Sustainable Horticulture

Monrovia Falters…Industry Feels the Tremors

Posted by sustainable_hort on February 2, 2011  |  No Comments

Monrovia’s recent sales woes may indicate that a new marketing message is needed to revive a shell-shocked consumer.

I now look back at my years working for the Oregon nursery industry and realize it may have been a Golden Age for wholesale plant growers. The state’s sales skyrocketed over several decades from few hundred million to nearly one billion. Then it all collapsed. As the housing market dropped, so did landscape plant sales. Then, almost all commercial work stopped abruptly. Architectural firms shrank over night. This ripple hit the plant industry, especially the growers, and we have seen numerous growers go under or move into other horticultural crops. Sales this spring will probably improve slightly, but not enough to save many growers.

Monrovia has represented the peak of nursery industry production and marketing. Yet, like any industrial designed production systems, the operating costs are substantial. The company created new plants, led the “branding” effort (a marketing strategy that I always thought was over-sold), and used the garden centers to provide an effective distribution/sales platform. Now, with sales down drastically again, the company has been forced (by the banks) start selling “non-branded” plants to Home Depot to force sales. This obviously undercuts a basic part of their marketing/branding strategy of selling only to the independent garden centers. It has also created some severe comments from their customers.

But, it is not all their fault. All the quality products and clever marketing cannot “create” markets if there is, in this case, very little building going on. Add to this the panicked consumer…a one-two punch that has not just Monrovia but an entire industry on the ropes.

There are a few bright spots. Some narrow niche producers are keeping their sales at least even. Greenhouse operations that concentrate on annuals and especially vegetables are surviving. There was actually shortage last year of organic vegetable starts. Food costs, food safety concerns and a desire for better taste/nutrition are all driving this home garden trend. (See the next post on the urban homesteading movement.) A complimentary trend uses permaculture techniques to add native plants and create more plant diversity to draw beneficial wildlife.

But, the more general ornamental plant growers will need another marketing hook to push up sales. I propose turning to the strength of plants to provide a better, less polluting environment and lower energy use. I like to call the many uses of plants to improve our water and air a new “plant technology.” Sell plants because they provide solutions, not because they “decorate” our world. It is an old idea really. There is adequate research and successful examples to get consumers to look at plants, not as a “discretionary” expense, but necessary to improve one’s home and life. This “message” will sell better in the new consumer economy, one that is moving away from the wild spending of the last two decades.

Trees for CO2 Sequestration?

Posted by sustainable_hort on April 14, 2010  |  No Comments

(This is the first part of a two-part post on trees and CO2 sequestration, which looks at whether trees actually play a positive role. The second part will discuss the actual trees we should be using for this perceived benefit)

Trees can play an important, positive role in helping control the amount of carbon dioxide (CO2) in the atmosphere by absorbing that key greenhouse gas. The process, called “sequestration,” uses a tree’s photosynthesis to convert the problematic greenhouse gas to cellulose and oxygen.

As this concept has become more widely accepted and, as researchers continue to document trees’ benefits, it may expand market for some nursery crops. But, is all this excitement warranted, or do some recent questions contradict the enthusiasm?

What We Need to Know
The crucial questions at this stage become “does sequestration really work,” and if so, “which trees are most efficient at sequestration?” Research continues to delve into varietal and climate issues that affect how well a specific tree will capture CO2.

“We can certainly argue that trees, when they absorb CO2, buy us a period of sequestration,” said David Nowak, researcher at SUNY-CESF, Syracuse, New York.

But, Nowak, who has lead several major sequestration studies, points out there are many variables that need to be studied, including climate effects, tree species and age, and even the general maintenance issues.

“These all can impact the effectiveness of a tree to sequester CO2,” he said.

Other research has pointed out some distinct differences based on climate. In fact, recent computer models are even speculating that non-tropical trees might even increase planet temperatures.

But, planting trees in [any] climate is better than not. So, how does it work and what does research indicate as the best options for using trees to reduce atmospheric CO2?

What is Sequestration?…Removal of Air Pollutants
Air pollution can be reduced dramatically when plants take up CO2 and many airborne particles through their leaf stomata. Some other gases are removed by the plant leaf and stem surfaces. Gases absorbed by the plant stomata later diffuse into intercellular spaces. They then are absorbed and react with water films to form acids, or they react with inner-leaf surfaces. Some particles can be absorbed into the tree, though most particles that are intercepted are retained on the plant surface.

Some polluting particles may return to the air during transpiration or be washed off by rain. Later, the leaf and twigs may drop off the to the ground and start to decompose. This also releases some of the CO2 back, which offsets some of the early gains. Consequently, vegetation remains only a temporary site for retaining many atmospheric particles.

Benefits of Trees
Plant-It 2020 uses a ‘scientific estimate’ to develop the following statistics based upon the tree species, soil conditions and tree-planting methodology,

Their research indicated that 600 trees in the tropics would fill one acre, which could sequester up to 15 tons of CO2 annually. Other statistics include 40 trees (common varieties) will sequester one ton of CO2 each year; and that one million trees covering 1,667 acres could capture 25,000 tons of CO2 annually.

Research in major metropolitan areas showed the urban forests could have an impact. It was reported by David J. Nowak in “The Effects of Urban Trees on Air Quality” showed that in 1994, trees in New York City removed an estimated 1,821 metric tons (t) of air pollution at an estimated value to society of $9.5 million.

His research showed that while New York’s urban forests removed pollution more than Atlanta’s (1,196 t; $6.5 million) and Baltimore (499 t; $2.7 million), but pollution removal per square meter of canopy cover was similar among these cities (New York: 13.7g/m2/yr; Baltimore: 12.2 g/m2/yr; Atlanta: 10.6 g/m2/yr). These standardized pollution removal rates differ among cities according to the amount of air pollution, length of in-leaf season, precipitation, and other meteorological variables. Nowak’s work noted that large healthy trees (greater than 77 cm) annually remove about 70 times more air pollution (1.4 kg/yr) than small healthy trees (less than 8 cm in diameter) at 0.02 kg/yr.

His 2002 work matched earlier research regarding total CO2 sequestered within the US. Total carbon storage by urban trees in the coterminous United States is estimated at 700 million tons. These data correspond with previous analyses that estimated national carbon storage by urban trees as between 350 and 750 million tons and between 600 and 900 million tons. Carbon storage by urban trees nationally is only 4.4% of the estimated 15,900 million tons stored in trees in USA non-urban forest ecosystems. The estimated carbon storage by urban trees in USA is equivalent to the amount of carbon emitted from USA population in about 5.5 months based on average per capita emission rates.

The research reported that “urban forests in the north central, northeast, south central and southeast regions of the USA store and sequester the most carbon, with average carbon storage per hectare greatest in southeast, north central, northeast and Pacific northwest regions, respectively. The national average urban forest carbon storage density is 25.1 t/ha, compared with 53.5 t/ha in forest stands.”

He felt this data could be used to help assess the actual and potential role of urban forests in reducing atmospheric carbon dioxide, a dominant greenhouse gas.

Nowak’s research report stated the following:
“Air quality improvement in New York City due to pollution removal by trees during daytime of the in-leaf season averaged 0.47% for particulate matter, 0.45% for ozone, 0.43% for sulfur dioxide, 0.30% for nitrogen dioxide, and 0.002% for carbon monoxide. Air quality improves with 2 increased percent tree cover and decreased mixing-layer heights. In urban areas with 100% tree cover (i.e., contiguous forest stands), short-term improvements in air quality (one hour) from pollution removal by trees were as high as 15% for ozone, 14% for sulfur dioxide, 13% for particulate matter, 8% for nitrogen dioxide, and 0.05% for carbon monoxide.”

Meanwhile, www.plantit2020.org, has summarized recent forestry science studies in carbon sequestration related to trees, including the following:

The U.S. Forest Service estimates that all the forests in the United States combined sequestered a net of approximately 309 million tons of carbon per year from 1952 to 1992, offsetting approximately 25% of U.S. human-caused emissions of carbon during that period.

The US Forest Service also feels that large diameter; long-lived, leafy trees are more beneficial in regards to carbon sequestration. For example, they point to the fact that Atlanta’s 9 million-plus (mostly mature, broad-leafed) trees absorb about twice as much as Calgary, Canada nearly 12 million trees (many conifers).

They also noted that tree species is a strong determining factor regarding carbon sequestration, which vary by species in their rate of storing carbon, though research is still needed.
But, as a counter action, trees also vary in how many and how much harmful volatile organic compounds (VOC’s) they emit. One common example is isoprene, which produces the greenhouse gas ozone.

So, the best tree species is one that rapidly sequesters carbon but does not register high outputs of VOC’s. Long-lived trees (those living more than 50 years) are preferred by the Forest Service for carbon sequestration as dead trees rot – releasing all of the carbon that has been stored. US Forest Service recommends the following species for the United States…American basswood, dogwood, Eastern white pine, Eastern red cedar, gray birch, red maple and river birch.

Nowak does point out that the placement of trees actually has more impact that sequestration.
“The bigger impact comes from planting a tree in the proper location where it can provide cooling for buildings,” he said. “Just by preventing the added CO2 being emitted during air conditioning, trees can have four times the impact they have in sequestration.”

So, there are many functions to consider to maximize a tree’s impact on the environment, he cautioned.

Tropical Versus Temperate Zones
Another study, lead by Lawrence Livermore National Lab, indicated that trees planted closer to the equator sequester more carbon than those planted far to the North. Why this might have happened is still unclear. Some expert speculated that Southern tree species are often larger, long-lived, leafy trees compared to northern species.

Their computer models seem to confirm this observation. They built a model to determine the impact on temperatures forests have in different parts of the planet.

They focused on three key factors in their analysis:
• Forests can cool the planet by absorbing the greenhouse gas carbon dioxide during photosynthesis.
• They can also cool the planet by evaporating water to the atmosphere and increasing cloudiness; a deck of white clouds reflects incoming solar radiation straight back out into space.
• But, trees might also have a warming effect. They are dark colored, absorb sunlight and hold heat near ground level

“Our study shows that tropical forests are very beneficial to the climate because they take up carbon and increase cloudiness, which in turn helps cool the planet,” explained Dr. Bala, an author on the Livermore study.

So, the further you move from the equator, the more these gains are eroded she stated. The team’s modeling predicts trees planted in mid- and high-latitude locations could cause a net warming of a few degrees within a hundred years.

“The darkening of the surface by new forest canopies in the high-latitude boreal regions allows absorption of more sunlight that warm the surface,” Dr Baal said.

Counter Views
But, despite the general excitement over planting trees, no, literally planting forests as a solution to global warming, has hit some speed bumps recently.

In addition to the Livermore computer model concerns, two other recent papers in the scientific literature raised questions about the benefits of terrestrial carbon sinks. One paper, by Frank Keppler, Max Planck Institute, discovered that plants emit significant amounts of methane, which is a potent greenhouse gas, which traps heat much more efficiently than CO2.

Another study, by Robert Jackson, Duke University, found that plantations could reduce stream flow and increase salinization of soils to a greater extent than previously recognized. It looked at existing conversions and showed that the growing trees had larger water demands than crops or pastures “dramatically decreased stream flow within a few years of planting,” the authors wrote.

They also found that water use within existing tree plantations of all ages resulted in average stream flow reductions of 38 percent. Losses increased as the trees age, and “13 percent of streams dried up completely for at least one year,” the study said.

Overall, the tree farming used about 20 percent more rainwater, the study estimated. So, additional tree planting for carbon mitigation could have large impacts on nation’s water resources. This is ore of an issue in nations that net less than 30 percent of their total annual supplies of fresh water from rain, the authors predicted.

This has lead to experts some questioning the overall tree planting strategy, but others view this speculation as overblown.
Nowak also cautioned that urban tree management practices could diminish the net effects of urban trees on atmospheric C02. Activities used to maintain vegetation structure and health (e.g. from chain saws, trucks, chippers, etc.) emit carbon via fossil fuel combustion. Thus, too much maintenance could cause urban forest ecosystems to become net emitters of carbon unless secondary carbon reductions (e.g. energy conservation) or limiting of decomposition via long term carbon storage (e.g. wood products, landfills) can be accomplished to offset the maintenance carbon emissions

“Carbon released through tree management activities needs to be accounted for to calculate the net effect of urban forestry on atmospheric carbon dioxide,” he said.

He argues that unless there are secondary carbon reductions (e.g., energy conservation) or limiting of decomposition via long-term carbon storage (e.g., wood products, landfills), urban forests lose much of the sequestration gains. This, in turn, affects the species composition and tree maintenance activities chosen for an urban forest.

Some Conclusions
So, where does all this leave with trees and their effects on CO2 sequestration?

To maximize the net benefits of urban forestry on atmospheric carbon dioxide, Nowak wrote that urban forest managers should focus on the following:
• Planting long-lived, low-maintenance, moderate to fast-growing species that are large at maturity and matched to site conditions;
• Using maintenance activities that increase tree survival and longevity;
• Minimizing fossil-fuel use related to management and maintenance activities;
• Using wood from removed trees to delay decomposition or decrease the need for energy from fossil-fuel-based power plants (e.g., develop long term wood products; burn wood to heat residences); and
• Planting trees in energy-conserving locations.

This was summarized clearly by Greg McPherson in a Arbor Age article “Urban Tree Planting and Greenhouse Gas Reductions.”

He wrote that…”The climate benefits of trees in mid-latitude cities are not an illusion, although they certainly feel good. Reductions in atmospheric carbon dioxide are achieved directly through sequestration and indirectly through emission reductions. Still, planting trees in cities should not be touted as a panacea to global warming. It is one of many complementary bridging strategies, and it is one that can be implemented immediately. Moreover, tree planting projects provide myriad other social, environmental, and economic benefits that make communities better places to live.”

Thus, while CO2 absorption can be positive, putting the right tree in the right place remains critical to optimizing its benefits and minimizing conflicts with other aspects of the urban infrastructure.

Next part…coming soon. We will look at where trees work best, which trees might be the best, and include a long list of references on this topic. See you soon.

What Is Sustainable Horticulture?

Posted by sustainable_hort on March 24, 2010  |  No Comments

This is a quick thank you to all that have checked this blog and made so many positive comments. And more…a short view of where we are headed.

This blog was started to document, explain, revise, suggest and predict where the wide world of horticulture can honestly to create systems to grow plants that do not depend on petroleum based inputs (which at some point become scarce or at least much more expensive), but finds closed systems to supply those inputs. No one is saying it is easy, it still needs work and research, but natural systems are being identified. We just need to rethink some obvious biology, especially relating to soil, and how it has worked “sustainably” for millions of years.

Definitions are tricky…and “sustainability” is seems to be the rule in this case. There are many definitions, the majority of which tend to be bent to service those defining it. But, after reading numerous definitions, it seems to boil down creating ways to grow plants that will without harming workers or future generations later. Many include the definition of “environmental health, economic profitability, and social and economic equity.” This must mean “we must meet the needs of the present without compromising the ability of future generations to meet their own needs.” So, “stewardship” requires “maintaining or enhancing this vital resource base (soils, water and closed inputs) forever.”

Certain food and ornamental products have identified with this “sustainable” vision. More than identified, they have built businesses, created organic fertilizers and pesticides, established networks and distribution systems that are a first stage in creating a more sustainable horticulture. It might even lead to a more sustainable agriculture…a different conversation.

Even Miracle Grow, not the most organic product in the world, is now selling two soil amendment products. These miracle products, which the company promotes as containing “organic” components, promise healthy soils that “grow plants twice as large.” The company has recognized the concept, along with much of agriculture, that healthy soil is the literal and environmental foundation of sustainable horticulture, whether in farms or landscapes.

So, this blog first focuses on ornamental plant production. I am working with a wholesale grower in the wonderful Willamette Valley, Oregon, where plants like to grow. It is one of the main reasons I live here today. We are seeing if a grower of shrubs and trees can work towards a sustainable sustainability…one that works economically long term. A key phrase in this sentence is “long term.” And it may mean growing not the largest plant, but the healthiest plant. This is not just speculation, but has a background, starting with the works of Sir Alfred Howard and William Albrecht, and continuing today with the Rodale organization, the Leopold Center for Sustainable Agriculture, and ATTRA. I suggest reading New Opportunities in Sustainable Landscapes and Can Nurseries be Sustainable? on this blog, and investigating the references. Let’s keep the discussion going.

At the same time, this site will point to new uses of plants from green roofs and walls, to storm water control with green streets, to growing food on empty rooftops and in our neighborhoods. We find cities planting more trees, urban agriculture sneaking into backyards and along cities edges, plants being used to clean water and air, and cool our heat islands. This is all positive and needs to be recognized as an important environmental strategy, one that can also create jobs. Obviously, without plants, there is no food or air, there is no “us.” So, it becomes important to recognize and utilize plants at every level we can.

Finally, this discussion site will lead to the introduction and testing of organic input products here in the Northwest (with application nationally), and we will be providing some of those products through this site and with advertising support. This all works toward my focus, helping horticultural growers (both food and ornamental) move, step by step, to a sustainable future while still providing the planet with plants.

And, a main test site will be our organic produce operation, 19th Street Farms. Since the links on this template are not working right, just type in “www.19thstreetfarms.com/blog/” to get to the site. I will use this blog for other content, but the site will busy in summer. It is also our CAS/Farmers Market site where we are continually talking with our customers. So look under specific categories for your favorite topic.

MORE COMING SOON…

Plant Lists for Bioswales and Rain Gardens

Posted by sustainable_hort on March 18, 2010  |  No Comments

This post, as promised, presents a quick overview of the various plants used in bioswale and rain garden environments. It is not as simple as just throwing a few water tolerant plants in the ground. Careful plant choice and placement play key roles in successful “wet” landscapes.

Plant selection for these projects is driven by several key factors including the following:

Obviously, the basic site conditions play a huge role. Factors like sun exposure, soil depth, physical and chemical properties and moisture holding capacity can vary, so need to be understood for successful plantings.

What is the intended function of the project? For many projects, the landscape’s performance, including infiltration, pollutant removal and evapotranspiration rate will determine its success.
But, there can also be safety issues, which may require added protection such as surrounding hedges. Finally, aesthetics play a role since many working landscapes sit in neighborhoods and other public areas. While visible, they can seen as an amenity, and even provide some recreational opportunities.

No landscape is going to be maintenance free; so long term needs should be studied. This is one area where the plant material choice can have dramatically different cost impacts.
Finally, recognize each site’s natural water regime. Check the depth, frequency and duration of soil saturation, which will vary daily, seasonally or annually. For instance, Portland, Oregon, is considered a “wet” climate, but the summer is extremely dry. Plants in these urban, constructed wetland must survive extreme variations. A similar garden in Atlanta, Georgia, or Columbus, Ohio, would get significant summer rain.

Actually every rain garden or bioswale has its own “zones” that have different requirements, according to the Virginia Department of Forestry’s Rain Gardens Technical Guide. The guide points out that the center, and deepest, part of the garden best grows the very wet to wet-loving plants. Meanwhile, the middle of the garden’s side takes wet to dry plants, while the upper rim takes drier types of vegetation.

The guide lists other factors affecting the choice of the plants for rain gardens:
• Decide on objectives, such which wildlife you want to attract, then decide on the varieties you would plant to attract those species. [Refer to reference list below]
• The rain garden’s location affects use of fruit-bearing plants and trees, since if it is near the driveway or walkway, it could create messes and maintenance issues. Trees next to a power line or too close to a house are not good choices.
• If the bioswale are near enough to receive runoff from a road that gets chemical treatments for ice in winter, choose plants that tolerant salt.
And then there is actual selection of species and varieties…and a common question, should we plant natives compared to introduced, commercial varieties?

Why Native Plants?
The majority of the web sites that deal with bioswales or rain gardens are also now recommending using natives. So, why is this the accepted trend?

As Withrow-Robison and Johnson point out in the OSU publication Selecting Native Plant Materials for Restoration Projects, “selecting appropriate plant materials for restoration projects helps make any of these projects more successful. They state that, “‘appropriate’ means choosing species that are suitable for the site, are grown from locally adapted sources, and have a solid genetic composition.” In many cases, this leads to using native species.

So, what is a “native plant?” Most definitions say a “native plant” occurs naturally or has existed for many years in an area, and they can be trees, flowers, grasses or any other plants. “Local adapted sources” can mean those plants have adapted to a very limited range, living in unusual environments, under very harsh climates, or growing in unique soil conditions. Yet, while some had a very limited range, many others live in diverse areas or easily adapt to different surroundings.

So, to summarize the strengths of using natives in bioswales and rain gardens.
• First, native plants are better adapted to the local climate. Once planted and established, do tend not to need extra water or fertilizer.
• Secondly, many are deep rooted, allowing them to survive droughts. This is especially important in the Northwest, where the normal wet weather can disappear for several months during the summer months.
• Third, native plants provide habitat and food for native wildlife and, are thus very attractive to the diverse native bees, butterflies, beetles and birds, all important pollinators.

These plants, which include many wildflowers, sedges, rushes, ferns, shrubs and small trees, grow on the edges of natural wetland, also have root systems that enhance infiltration, moisture redistribution, and diverse microbial populations involved in biofiltration.

A key point to remember is that rain gardens, unlike a water garden, will be dry most of the time. Plant selection should include those that tolerate short periods of inundation, but not require constant standing water. In areas that will have moist, well-drained soil, select plants with moderate moisture requirements. For drier sites like the edge of your rain garden, plant species with low or moderate moisture requirements.
Meanwhile, any perennial plants need to be hardy in your growing zone.

Each region has growers of appropriate native and related plants for rain gardens and bioswales.

In fact, some successful growers will collect seed their own seed from the local area. For example, one Oregon native plant producer has collected seed for plants such as snowberry (Symphoricarpos albus), salmonberry (Rubus spectabilis) and twinberry (Lonicera involucrate) in the immediate area, using on a couple of mother plants for each. Another grower collects all her Pacific dogwood (Cornus nuttallii) from two trees growing at a nearby park.
See references below for several recommendation lists.

These three urban plant technologies are just part of a wider set of alternative Best Management Practices (BMPs). Many are simple, practical designs, but provide effective storm water management. Some even add aesthetic enhancements to the urban, suburban, and rural landscapes. They can be cost effective to build while providing long-term sustainability for city infrastructure and conservation of a city’s water resources. These include filter strips, grassed swale, green roof, and infiltration basin, planters and trenches.

So, as the cost savings are identified, the demand for specific plant materials should increase. At this point, the trend seems to be moving toward regionalized, native plant materials. Since there are a number of operations already propagating this niche, they may have the best opportunity to benefit from this particular green movement.

References:

The following references are available online and have been updated relatively recently, so they contain more current research and data regarding various plant choices.

• Rain Gardens Technical Guide Virginia Department of Forestry
www.dof.virginia.gov/mgt/resources/pub-Rain-Garden-Tech-Guide_2008-05.pdf

• Selecting Native Plant Materials for Restoration Projects by B. Withrow-Robinson and R. Johnson, OSU publication EM 8885-E, November 2006.
extension.oregonstate.edu/catalog/pdf/em/em8885-e.pdf

• Plants for Stormwater Design
www.wildflower2.org
Native plant database and suppliers directory for North America.

• Rain Gardens Technical Guide – Virginia Department of Forestry
Central Office
900 Natural Resources Drive, Suite 800, Charlottesville, Virginia 22903
www.dof.virginia.gov
Phone: (434) 977-6555 – Fax: (434) 296-2369
VDOF P00127; 05/2008

• Brooklyn Botanic Gardens, Rain Garden Plants.
This web site offers regionalized lists of suggested plants for rain gardens. Not as extensive as other sites, its easy to use breakdown is a good starting place in identifying plants for an effective design palette. www.bbg.org/gar2/topics/design/2004sp_raingardens.html

• 10,000 Rain Gardens (www.rainkc.com) has an extensive site that features a diverse list of plants for rain garden situations. It also has a search feature that allows criteria selection from five categories, so a nursery could focus first on what it is already growing, expand to closely related varieties, and then look for new opportunities that would fit within existing production systems.

• Bluestem Services: (www.bluestemservices.com) Has numerous plants lists, but two feature nearly 100 plants for rain gardens and wetlands.

Worm Culture…Helping Save the Planet

Posted by sustainable_hort on March 9, 2010  |  No Comments

OK…I admit the headline is a bit overblown…but I have been encouraged by recent increased activity around using worms to recycle bio-materials, mainly food waste.

I have personally followed the vermiculture movement for decades, since these hard working organisms both help create healthier soils and are indicative of them. My static compost bins have long since turned into worm bins, and more than handle all our food waste. I have even been testing commercial worm castings in a container plant production system as part of an organic mix.

Equally important is the idea that vermiculture might be an answer to one of our concerns…getting rid of food waste. Most of it now travels to a landfill site to be buried with all the other “garbage.” But, is it really “garbage” or “waste?” Current vermiculture systems can take the mountains of food waste and turn them into worm castings (poop), a rich and biologically active soil amendment.

While many authors have praised worm castings as improving soil health, there has been limited research into how they affect plant growth. But, a recent study at North Carolina showed that adding “vermicompost” to the container mix for Hibiscus plants showed dramatically improved growth with a 20% compost mixture. For more information, contact Michelle McGinnis at michelle_mcginnis@ncse.edu.

I have seen similar results in my testing.

If you don’t believe there is a food waste issue, read the book “Waste” by Tristram Stuart. This covers the food waste issue world wide, with many depressing statistics on how much food gets thrown out. In fact, studies show that “around half of all food in the US is wasted!” And, this is a trend that has tended to increase over the past few decades. So, the raw material is there…we just need systems to collect, process and distribute this potential soil builder. It would solve several problems at once.

In fact, here in Portland, there is a neighborhood activist, Randy White, who is trying to organize neighborhoods into worm composting centers. (He can be contacted through his website “Bright Neighborhood” at www.brightneighbor.com.) Those in the specific area would invest $250 and contribute all their food waste to their local worm farm. The wastes would turn into soil food and given to those that supplied the raw materials…recycling within the neighborhood

If you don’t know much about this, a good place to start is with the website www.vermiculturemanual.com/en/index.html. It lists links to courses, and contains lots of basic information. Or, you can get much of what you need free with the “Manual of On-Farm Vermicomposting and Vermiculture” by Glenn Munroe (Organic Agriculture Centre of Canada). This PDF publication is available online at www.agbio.ca/DOCs/Vermiculture_FarmersManual_gm.pdf.

Other books include “In Their Own Words: Interviews With Vermiculture Experts” edited by Peter Bogdanov; and “Beyond Compost: Converting Organic Waste Beyond Compost Using Worms” by Tom Wilkinson. They are available through online sites…just type in “books on vermiculture” to find them.

This site will follow this activity, both locally here in Portland, and internationally. It is just one of what I like to call a “middle-of-the-road-radical” solution to a problem. One where it seems everyone, including the public in general, gains something positive.

Plant Lists for Green Roofs Continues to Expand

Posted by sustainable_hort on February 27, 2010  |  No Comments

Every green roof requires plants of some kind. While various succulents have proven relatively dependable in a roof’s harsh environment, there are many research projects looking at many other plants. As the results come in, new opportunities for the nursery industry and growers will appear.
But, at this point, there still seems to be a rather limited view of what plants might be best on our roofs. This post is part one of a two part article on green roof plants and environments. The second section will look at the basic types of green roofs we now see being built. This post also contains an extensive reference list.

Plants for Roofs
When reviewing plant use on green roofs, it is useful to first divide the discussion into “extensive” or “intensive” use.
“Extensive” roofs are generally installed for environmental/ecological reasons, not as additional human living space. If the roof is visible from surrounding buildings, the plant material may be irrigated, but often it is not watered. So, only tougher varieties that can go dormant for dry periods are chosen.
Define “intensive”…Moves beyond the purely environmental uses to creating livable spaces…multi-use spaces defined and enclosed in almost traditional landscape plantings though many of the plants are at a smaller scale. Use of containers, raised beds, and deeper soils allow for larger and vertical varieties. This concept is more developed in
Europe, though the re-urbanization movement with more concentrated condo living may demand more of these spaces be developed.
Yet, even within the more limited “extensive” options, the plant palette is still a work in progress. As Nigel Dunnett and Noel Kingsbury wrote:
“The horticultural potential of green roofs has yet to be fully realized. The majority of extensive green roof rely on a small number of species and cultivars that are use ubiquitously.”…”Widening the range of plant species used beyond the widely used sedum carpets has many potential benefits.” (b)

Broadening the Research on Plants for Green Roofs

Part of what Snodgrass called being “discovered” was all the research on the plants and soils for these roofs that has exploded in the last several years. After some notable green roof failures (see below), specific plant research is acutely needed so regional collections can be developed that will be successful in most situations.

Soil Depth Key to Plant Variety Success
Soils are one area of active research. The proceedings of the Green Roofs for Healthy Cities annual conference contain many reports and papers on soil make-up and depths relating to successful plant establishment on green roofs.
Add decades of practical experience, especially in Europe, and there are some basic parameters on soil depth and successful plants. The shallowest soils, with only 2 – 3 cm (0.8 – 1.2 inches) of medium, will grow only sedums and mosses. Substrate depths of 5 – 8 cm (2 –3.2 inches) support a wider range of succulent species, grasses, and herbaceous plants. Depths of 10 – 20 cm (4 – 8 inches) allows for a wide range of drought-tolerant perennials and grasses to be grown, as well as tough sub-shrubs. These depths will also support turf grass and lawns. Depths of 30 – 50 cm (12 – 20 inches) will support many perennials and shrubs to be grown. Trees generally need depths of 80 – 130 cm (32 – 52 inches).
The soil media composition is just as important as media depth to plant variety success. The percentage of organic to mineral matter, and the organic source material’s nutrient providing capacity, both play roles in the plants’ success. There are many ongoing research projects that will help determine which of the various media mixes work best in specific climates and situations. Soils need regional versions, similar to the choices with plants.

The Regional Need…
It is also generally accepted that one plant, or even one plant family, will not fit all the varied roof environments, due to both climate and differences in roof height and configuration. As mentioned above, nurseries like [Snodgrass] recognized the trend early, began with plants already successful in the regional climate, and began supplying contractors.
Nigel Dunnett discussed the same issue, stating…”because roof greening originated in central and northern Europe, the limestone meadow flora of this region has tended to dominate the plant-selection…partly because of its eminent suitability and partly because a variety of seed mixes are readily available. Yet, outside this region this limestone meadow flora may be regarded as inappropriate or potentially unsuccessful, particularly in areas with longer and hotter summers, making it important that local mixtures are investigated for their suitability instead.” (e)
The Northwest climate is a perfect example of a region that is probably not well understood. It has an image of grey skies and rain, yet is has a Mediterranean climate with little summer rain. This is different than much of the US that can have significant summer rains.

Early Northwest Project Teaches Hard Lessons
In fact, an early eco-roof in Portland provided a lesson in what not to do. The project, a green roof on the new Brewery Blocks development in northwest Portland was designed by Gerding Edlen Development. They eventually faced challenges at three points: drainage, soil and plants selection.
First, they misjudged the need for some slope in the drainage pattern. Since run-off was to be slow, they felt the level roof should not prevent water from eventually moving off. But, the roof was not completely level, and their drainage boards were too thin, leading to a pooling of water. Many of the plants did not like their “feet” wet and died.
Then, the soil had too much organic material. Most successful green roof soils have a small percentage (no more than 10%) organic material and are mostly made of inert materials such a perlite, ground lava rock, and other light-weight materials. In fact, many of the successful genera and species thrive in low-nutrient, sandy conditions, as mentioned above.
Finally, there was the plant selection. When designed in 2002, there was limited information on green roof plants. GED looked to Europe, borrowed many of the German succulents. But, they did not survive Oregon’s wet winters and very dry summers.
These problems were solved several years into the project by just starting over. Lessons learned, more information available, and hiring several experience consultants helped turn it around.
GED partner Dennis Wilde summed up the experience:
“First, hire landscape architects that have vegetated roof experience,” he stated in a 2008 Eco-Structure magazine article. “(Then), develop a deep understanding of the drainage, soil and plant issues you need for a successful installation.” (r)
At this point, most regional research continues to concentrate on plants that evolved in exposed soils, often mountainous areas, with rocky, sandy or xeric conditions. Adapted to cope with a lack of water, the plants have a morphology (see below) that stores water and reduces water loss. Many have fleshy leaves and stems that help deal with drought and high temperatures, with Sedums being the dominant choice. (n)
Dunnett presented research that showed there runoff was not generally affected by vegetation complexity or taxonomic composition of the communities. He noted seasonal differences. The winter months’ high precipitation quickly saturated the soil run-off was similar from all treatments. In the summer, with intermittent rains, run-off differed in relation to the plant canopy structure, where precipitation is lost to interception, stem flow and evaporation, along with transpiration.” The thicker the vegetative cover during low rain periods (summer), the more effective the roof is at capturing rain.(z)

Heavy Use of Sedums (Succulents)
As mentioned above, the heavy use of sedums is based on their survival rate in generally harsh environments. These plants will both store water and have a special type of metabolism called ‘Crassulacean Acid Metabolism’, CAM for short. CAM plants are unique in that under drought conditions their stomata (leaf pores) are open at night rather then during the day, as is the case with most plants. CAM plants exchange gasses (oxygen and carbon dioxide) in the dark when it is cooler and less windy. CAM plants are up to ten times more efficient with water conservation than non-CAM plants.
Many of these same plants will also go dormant, particularly during the drier periods. This is particularly important in the west coast’s Mediterranean climate. While some regions actually have a “wet” reputation, these states can be relatively dry from late spring until mid-Fall. This is in direct contrast to much of the US where summer rains are common.
This gives them a decided advantage when green roof conditions dictate certain limitations. Thus, the majority of green roofs you visit will have at least some sedums and succulents. Some roofs will be nothing but these plants.

Research Confirms Sedum’s Strengths
2006 research from Michigan State University tested sedum’s repudiated superior performance in low water conditions, common on green roofs. 25 Sedums were compared to several Michigan natives. The plants were watered at varying intervals. The non-sedum natives only survived if they received water every two days. In contrast, several sedum varieties were alive after 89 with no water. (a).
These plants have been used in Europe for decades, so early U.S. designers borrowed the palette without necessarily having the same climate. Results have been less than perfect. This may be due to the fact that much of Germany receives significant rain amounts in the summer and different winter conditions than many U.S. regions.

Nurseries Find Success with Succulents
Emory Knoll Farms, now possibly the largest U.S. green roof plant nursery, currently grow more than 100 different varieties for green roofs. Snodgrass’ choices are based on European sedums, selections from the Denver Botanical Garden, and many plants from South Africa, particularly the Ice Plant varieties. (d)
Green Living Technologies lists nearly 50 Sedum cultivars that are used in their hybrid mat-layered systems (see more below).
Intrinsic Perennial Garden is another supplier of green roof plants, They even have their own blend of native plants called the BIO-diver-CITY™ Blend These are Midwest native plants selected by Intrinsic Perennial Gardens, Inc. after trialing over 100 plants for the tough conditions of a green roof environment in the Midwest. (x)

Grasses
Green roof varieties drop off quickly after the sedums and related plants. A more limited range of grasses have also been successful, including many Festuca and Carex choices/
Grasses usefulness in green roof planting depends significantly on soil depth. Research indicates that very shallow soils (5 cm and less) will only support a couple small Festuca species and a restricted range of short sedges (b). Thus, the Festuca species appear on many green roof plant lists.
Yet, grasses continue to be popular choice since many can go dormant and revive vigorously when watered, or the rains return. Yet, several authors have noted a concern that they might create a fire hazard. This may represent another area of research.
Still, other varieties are suggested for use on green roofs. These include the following grasses and grass-like plants.
• Agrostis pallens (Bent grass)
• Calamagrostis stricta (Slimstem reedgrass)
• Panicum virgatum (Switch grass)

Other Choices
Meanwhile, the more aggressive nurseries are now offering the following plants: ferns, Alliums, many herbaceous perennials, and even mosses. The research below contains many newer choices now being tested.
It was surprising that research showed mosses might play a more important role in establishing a green roof than has been recognized. A recent paper discusses the BRYOTECH Process, a method developed for the industrial production of pioneering plant mosses associated with microorganisms. The authors provide brief summaries of results of studies that explored the effects of soils with a “biological crust” on plant growth and performance. According to the authors, mosses and other symbiotic plants and soil micro-organisms can create green roofs that immediately incorporate the living elements that nature would introduce over a much longer period of time: micro-organisms associated with mosses, and wild seeds of dependent xerophilous plants. The need for maintenance of plants and the use of fertilizers is greatly reduced. The various studies and works carried out by the firm MCK Environment demonstrate that the use of mosses is key in re-vegetating land where colonization is particularly difficult. This principle is also applicable to green roofs. (t)

References:
Those interested in plants for green roof should get a subscription to “Eco-Structure” magazine (www.eco-structure.com); and “Living Architecture Monitor,” published by Green Roof for Healthy Cities, (www.greenroofs.org).

(a) Evaluation of Crassulaceae Species on Extensive Green Roofs. Durhman|VanWoert|Row|Rugh|Ebert-May, Angela K. |Nicholaus|D. Bradley|Clayton L.|Diane. Proceedings: Greening Rooftops for Sustainable Communities 2004, 2004, 3.6.

(b) Plant Options for Extensive and Semi-Extensive Green Roofs. Nigel Dunnett and Noel Kingsbury. Proceedings: Greening Rooftops for Sustainable Communities. 2004 conference proceedings, 2.2.

(c) Native Coastal Plants for Northeastern Extensive and Semi-Intensive Green Roof Trays: Substrates, Fabrics and Plant Selection: Jeff Licht, EdD, LLC, Jeremy Lundholm, PhD Wayland, MA, Roof Garden Consultant / St. Mary’s University, Halifax, Nova Scotia, Canada Rooftops for Sustainable Communities 2006, conference proceedings, 4.3.

(d) Green Roof Plants. A Resource and Planting Guide. Edmund C. and Lucie L. Snodgrass. Timber Press. 2006

(e) Planting Green Roofs and Living Walls. Nigel Dunnett and Noel Kingsbury. Timber Press. 2004.

(f) Rain Gardens. Nigel Dunnett and Andy Clayden. Timber Press. 2007.

(g) Plant Options for Extensive and Semi-Extensive Green Roofs. Nigel Dunnett and Noel Kingsbury. Proceedings: Green Rooftops for Sustainable Communities 2004 conference proceedings, p 16.

(h) Water-Efficient Plants for the Willamette Valley. Regional Water Providers Consortium publication. Information at www.conserveh2o.org.

(i) The Green Fuse: Using Plants to Provide Ecosystem Services. Sustainable Plant Research and Outreach (SPRout) publication. A literature review. Rene Kane. 2004

(j) Evaluation of Sedum ternatum in a Shaded Green Roof System. C. Hise, V. Jost, K. Luckett, S. Morgan, T.Yan, and W. Retzlaff. Southern Illinois University Edwardsville, 2006.

(k) Plant Species Evaluation for Extensive Green Roof Applications in the Midwestern United States. S. Kaufman1, V. Jost2, K. Luckett3, S. Morgan1, T. Yan1 and W. Retzlaff1. 1Southern Illinois University Edwardsville. 2006.

(l) Evaluating Plants in Green Roof Systems Following Establishment. Sydow M.1, K. Forrester2, V. Jost3, K. Luckett4, S. Morgan5, and W. Retzlaff1, 2. 1Department of Biological Sciences; 2Environmental Sciences Program; 3Jost Greenhouses; 4Green Roof Blocks, St. Louis MetalWorks, Inc.; 5Department of Civil Engineering; Southern Illinois University Edwardsville. 2006.

(m) Evaluating Green Paks Green Roof Systems. R. Lucas1, H. Luckie1, V. Jost2, K. Luckett3, S. Morgan1, T. Yan1 and W. Retzlaff1. 1Southern Illinois University Edwardsville, Ill. 2006.

(n) Native Survivors. By Ron M. Wik, Living Architecture Monitor, pages 24 – 25. Winter 2008.

(o) Hot and Humid, What Plans Work Best in Tropical and Subtropical Situations? By Steve Skinner, Living Architecture Monitor, pages 26 –27. Winter 2008.

(p) Drought…Evaluating the Performance of Green Roof Plants and Growing Medium. By Dr. Bill Retzlaff, Dr. Susan Morgan, Kelly Luckett and Vic Jost. Living Architecture Monitor, page 29. Winter 2008.

(q) Oregon State University Stater, Winter 2008, pages 21 – 26.

(r) Best Intentions, article by Jim Schneider, Eco-Structure magazine, April 2008, p. 44 – 47.

(s) Establishment and persistence of Sedum spp. and Native Taxa for Green Roof Applications, By Monterusso, Michael A., Rowe, D. Bradley, Rugh, Clayton L., Michigan State University. HortScience 40(2):391-396, April 2005.

(t) Mosses, A Necessary Step for Perennial Plant Dynamics. Chiaffredo|Denayer, Michel|Franck-Olivier.. Greening Rooftops for Sustainable Communities, Portland, OR, June 2-4, 2004, p. 9.

(u) 100 Extensive Green Roofs: Lessons Learned. Snodgrass, Ed. Proceedings: Greening Rooftops for Sustainable Communities, May 4-6, 2005, p. 6.

(v) White|Snodgrass, John W.|Edmund. Extensive Greenroof Plant Selection and Characteristics. Greening Rooftops for Sustainable Communities, p. 14.

(w) Whitlow|Compton, Thomas|Jeannette S.. 11-MAY-2006. A Zero Discharge Green Roof System and Species Selection to Optimize Evapotranspiration and Water Retention. Greening Rooftops for Sustainable Communities, Boston, MA, May 11-12, 2006, p. 12.

(x) Hauth|Liptan, Emily|Tom. 30-MAY-2003. Plant Survival Findings in the Pacific Northwest. Greening Rooftops for Sustainable Communities, Chicago, Illinois, May 30, 2003, p. 13.

(y) Rowe|Monterusso|Rugh, Bradley|Michael|Clayton. 01-JAN-2007. Evaluation of Sedum Species and Michigan Native Taxa for Green Roof Applications. Greening Rooftops for Sustainable Communities, Washington, DC , May 2-4, 2005, p. 13.

(z) Dunnett|Nagase|Booth|Grime, Nigel|Ayako|Rosemary|Philip. Vegetation Composition and Structure Significantly Influence Green Roof Performance. Greening Rooftops for Sustainable Communities Greening Rooftops for Sustainable Communities, Washington, DC, May 4-6, 2005, p. 10.

(aa) Taken from Blackdown Horticultural Consultants Limited’s PDF brochure, available at www.greenroof.co.uk.

(bb) Article “Just Add Water: Wetlands Green Roofs for Enhance Performance” in The Green Roof Infrastructure Monitor, Fall 2007, p. 6 – 9.

(cc) Houghten, F. C. et al. 1940. Summer cooling load as affected by heat gain through dry, sprinkled and water covered roofs. ASHVE Transactions. 46:231-242.

Trees Prove Valuable in Several Ways

Posted by sustainable_hort on February 21, 2010  |  No Comments

Several posts ago I mentioned several confirmed environmental benefits of planting trees. The good news keeps coming.

First, a study from the east coast indicates that trees are growing faster, probably due to the increase in CO2. The study, published in The Proceedings of the National Academy of Sciences, concentrated on hardwood stands in Maryland that were representative of east coast tree populations. The work showed trees were growing an additional two tons of plant material per acre annually as the CO2 levels have increased 12% in the last 22 years. This is another indication that plants may yet save the planet. Gaia in action.

Then, a recent article in the Oregonian (Portland, Oregon) cited a recent research study that estimated the added value of having full size trees in a yard was $7000! Of course, as the article points out, there are a lot of added costs. And, your neighbor that shares that shade tree also gains value from it presence…without the costs. I tended to focus more on the fact that trees improve land values, and not the article’s concern that the “neighbor” was not sharing the upkeep costs…only getting the value. This is definitely a positive study for those supporting more trees in our urban/suburban settings. Make them fruit trees and they are even more valuable.

Finally, another book to recommend…Between Earth and Sky by Nalini M. Nadkarni. Not another descriptive collection of trees for yards, this one specifically discusses trees and their “intimate connection” to us. It goes beyond economic value into a more spiritual connection that is demonstrated by our long relationship with trees.

Soil Health and Organic Fertilizers

Posted by sustainable_hort on February 12, 2010  |  No Comments

Below is another response to an online post. The basic question was “what are good organic fertilizers” and some responses questioned whether they work or not. These are my quick thoughts…the books listed below apply to sustainable horticulture in many ways.

First, I am not so sure that “plants don’t know the difference” between petroleum-based and organic nutrition. A healthy, vibrant soil community provides the nutrition, and often the protection, plants need to be in prime health. This does equal using “dry weight comparisons” as the measure of health. Plants can grow too fast, too much nitrogen actually enhances disease and pest issues, and NPK is not the only factor is consider in plant health.

There are some key works that support this idea of “healthy soils equals healthier plants,” some pre-World War II. I would suggest reading Health & the Soil and An Agricultural Testament by Sir Albert Howard, the works of Dr. William A. Albrecht, Science in Agriculture by Arden Andersen, and Ask The Plant by Charles Walters and Esper K Chandler. A more recent work, Healthy Crops, A New Agricultural Revolution, by Franci Chaboussou, examines 75 years of research in this area. It provides a fairly convincing argument against current application practices with nitrogen fertilizers and many pesticides and herbicides, since they can be shown to increase pest issues. Even recent popular works, such as Teaming with Microbes by Jeff Lowenfels and Wayne Lewis, are identifying a simpler approach to soils, what is in some ways, an older agriculture.

Secondly, I would agree there tends to be a lot of hype around these products…just look at the compost tea issue. Several decades ago, some organic products were being sold as “magic,” which over-shadowed similar products long-term benefits.

But, I went back to Oregon State University decades ago to study composting, got a horticulture degree, and ended up in the Oregon nursery industry, which grows many of its products in relatively artificial systems. I have tested the options, learned to grow most plants without excessive N, using organic pest controls (though few were even required). There is getting to be more research into soil health, we have major ag schools adding organic production to their curriculum, and the consumer is asking more questions. Meanwhile, my organic farm seems to be flourishing and early tests in a local ornamental nursery show “organic” shrubs and trees are not only possible, but may be even cost effective. These products work, you can achieve equal production, and many are sustainable…often taking consumer waste and turning it into plant food. These are natural cycles we should continue to tap.

Trees Saving the Planet?

Posted by sustainable_hort on February 1, 2010  |  No Comments

The New York Times is reporting that a new research report, being published in today’s issue of The Proceedings of the National Academy of Sciences, indicates that trees are growing faster, perhaps in response to the atmosphere’s added carbon dioxide. (http://www.nytimes.com/2010/02/02/science/earth/02trees.html)
This relates to my last three posts that discussed the increasing role plants will play in solving climate change issues. This plant and planetary reaction seems to confirm some of the Gaia theories of James Lovelock, see site: (http://en.wikipedia.org/wiki/Gaia_hypothesis).
So, does this mean that the cooler temperate regions might actually see increased growth of not only the natural vegetation, but agricultural crops as well? There are already early olive ventures in the Willamette Valley of Oregon, moving up from California. Will Oregon start growing oranges next? Or maybe avocados!
Follow this site as we investigate, synthesize and report on the new “plant technologies,” including green roofs, green walls, bioswales, higher respirating plant varieties, plant site placement, etc.

New Opportunities in Sustainable Landscapes

Posted by sustainable_hort on January 30, 2010  |  1 Comment

This article appeared in the Oregon Landscape Contractor’s magazine. It is related to my last post that discussed how growers, retailers and landscapers might take advantage of new “green” trends and technologies. This focuses on how “Sustainable Development Offers New Opportunities for Landscape Contractors.”
And…thanks for your many positive comments on my content. Much more to come.

Many major developers are ‘going green,’ not just for good public relations, but also as an economically beneficial strategy. Innovative landscape firms have a tremendous opportunity to join this effort, position themselves as “green,” and dramatically increase their business.
“These are not little changes, but this is a sea change,” explained landscape architect Paul Morris, speaking at the annual meeting of Oregon Landscape Contractor Association in December. By 2010, industry studies predict a $19 to 38 billion in the residential green building market, he said.
Morris works on planning and sustainable issues for Cherokee Investment Services, Inc., an international development firm. He said that his company has long recognized the many benefits of incorporating sustainable technologies into their projects.
“These are no longer just warm-fuzzy things we’d like to do,” said Morris. “There are calculable benefit costs that can now be identified.”
In fact, his company, with $2 billion in assets, is the leading private investment firm in “brown field” development, working on abandoned and idle industrial and commercial urban sites often with environmental degradation and contamination, distinguished from “green fields,” undeveloped land outside urban areas. It plans to spend $250,000,000 on remediation projects, he said.