Impact of Adjacent Allelopathic Trees and Anti-Allelopathism Potential on Green Roofs

Allelopathy is the little referenced yet extremely important green roof secondary design principle of the bio-chemical influences certain plants and trees have on other plants and in this instance - on green roof plants.  The Breaking Ground Green Roof planting area is surrounded on three sides by tall trees. Some of these trees are deciduous and loose their leaves during the winter, others like the laurel oaks keep leaf cover most of the year.


An alleopathic tree usually exerts negative influence on adjacent vegetation via a number of different processes including;

• Fog & dew drip
• Leaf litter
• Volatilization 
• Sap drip
• Pollen
• Other biological processes

Trees impacting the Breaking Ground Contracting green roof include;

• Triadica sebifera, Chinese tallow - western border of green roof
• Quercus laurifolia, Laurel Oak - northwestern corner and eastern side of green roof
• Platanus occidentalis, American sycamore - southeastern and southwestern corners of green roof

According to the University of Georgia, School of Forestry Resources , there are a number of significant allelopathic trees requiring attention when planting other plants nearby.  They include;

Strong Potential for Allelopathic Impacts 
Acacia spp
Acer saccharum
Ailanthus altissima
Celtis laevigata
Celtis occidentalis
Eucalyptus camaldulensis
Eucalyptus globulus
Eucalyptus spp 
Juglans cinerea
Juglans nigra
Leucaena spp
Myrica cerifera
Picea engelmannii
Platanus occidentalis 
Populus deltoides
Prosopis juliflora
Prunus cornuta
Prunus serotina leaf 
Quercus falcata leaf 
Quercus marilandica
Quercus rubra
Quercus stellata
Robinia pseudoacacia
Sassafras albidum
Ulmus americana


Moderate Potential for Allelopathic Impacts
Abies amabilis
Abies balsamea
Abies grandis
Acer circinatum
Acer negundo
Acer platanoides
Acer pseudoplatanus
Acer saccharinum
Aesculus glabra
Aesculus hippocastanum
Aesculus octandra
Arbutus menziesii
Carya illinoensis
Carya ovate
Corylus spp
Crataegus spp
Fraxinus excelsior
Ginkgo biloba
Gleditsia triacanthos
Juniperus monosperma
Juniperus scopulorum
Kalmia spp
Picea spp
Pinus banksiana
Pinus contorta
Pinus densiflora
Pinus edulis
Pinus elliotii
Pinus monophylla
Pinus ponderosa
Pinus sylvestris
Prunus pumila
Quercus alba
Quercus borealis
Quercus douglasii
Quercus gambelii
Quercus michauxii
Quercus shumardii
Rhododendron maximum
Rhus copallina 
Sorbus sitchensis
Tsuga canadensi



Slight Potential for Allelopathic Impacts
Abies concolor
Aesculus spp
Betula pendula
Carpinus spp
Casuarina spp
Cupressus macrocarpa
Fagus spp
Fraxinus spp
Larix decidua
Picea excelso
Pinus palustris
Pinus spp
Populus spp
Pseudotsuga menziesii
Quercus petraea
Quercus robur
Quercus rubra
Salix pellita
Sambucus racemosa
Sequoia sempervirens
Taxus brevifolia
Thuja plicata
Tilia americana
Tilia cordata
Tilia planifolia
Ulmus laevis
Ulmus parvifolia
Umbellularia californica

As mentioned, the BReaking Ground Contracting Green Roof will be adjoined by Chinese tallow trees, Laurel Oaks and American Sycamores.

Quercus laurifolia, Laurel oak - although literature suggests laurel oak does not possess allelopathic qualities, care should be given to potential impacts of pollen and flower litter.  The laurel oak adjacent the northwest corner of the green roof has stained the white TPO and covered the roofing material with a layer of leaf and pollen litter.  Though laurel oak may not exhibit direct allelopathic influence on the green roof plants, potential for covering the plants with litter exists.  Continued site inspection will be required to confirm any impacts on the green roof plantings.

Triadica sebifera, Chinese tallow - one medium height tree exists adjacent the western border of the BGC green roof.  Chinese tallow has been the subject of numerous allelopathic studies and research.  Interestingly, research exists to support the theory of Chinese tallow leaf litter and fog drip may actually support germination and shoot growth on adjacent plants.  In fact, Chinese tallow was shown to actually improve germination and growth rates in Little Bluestem, Schizachyrium


Importantly, the American Sycamores, Platanus occidentalis located in the southeastern and southwestern corners of the BGC green roof have the potential to exert significant negative influence over the green roof plants.   As indicated in the above list, American sycamore produces strong allelopathic effects.  Data exists showing the active ingredients, scopoletin and chlorogenic acid found in the sycamore leaf may interfere with the ability of stomata on certain plant's leaves to malfunction,  interrupting the vital processes of photosynthesis and either stunting plant growth or killing the plant.  Close observation will be required on the effects of the American sycamore on the entire green roof planting area and in particular, the southeast and southwest corner plantings.  Pruning of sycamore limbs away from the green roof may be necessary.


Finally, good green roof design incorporates the effects of adjacent trees and other vegetation and allelopathic effect possibilities.  Recognizing and dealing with a potential allelopathic problem is much easier and more cost-effective up front.  Know the basics of adjacent tree and plant allelopathism and how your green roof design integrates into a site with pre-existing trees.


One of the related positive issues of anti-allelopathism and green roof adjacent trees is a benefit derived from leaf micro-nutrient content.  Tomorrow's topic will explore the antithesis of allelopathic impacts and look at the potential biological and chemical benefits from adjacent trees.

Green Roofs & Invasive Plants - Wisteria, Wisteria sinensis

Botanical name : Wisteria sinensis

Wisteria

Family/Famille : Fabaceae

We have spoken about invasive plants and green roofs here in these posts before. 

The most recent discussion centered around Nandia, Nandina domestica and the Gainesville Regional Utilities Greenroof project. Fortunately, with the help of the Florida Wildflower Foundation the Nandina was removed from the planting schedule.

Yet another beautiful but invasive plant species green roof designers should be aware of is the very hardy and drought tolerant Wisteria.

Wisteria sinensis

Wisteria or Wisteria sinensis is listed by the Florida Exotic Pest Plant Council as a Category 2 plant.

I am the first to admit the attractiveness and scent from wisteria is almost too alluring to resist. However I have also seen first hand the damage the plant can do as it is practically choking to death many of the large sweetgum trees on our Urban Farm. One part of me says - it is worth the color and beauty but then common sense kicks in and I realize we must take care with the plants we use in our landscapes and especially on our green roofs.


There are many alternatives for green roof plant use including both native species and landscape friendly species - species not native to an area yet also not considered invasive.
As mentioned in the post:

"The Florida Friendly Landscape program, an effort of the University of Florida and Florida's Water Management Districts, offers a concise and effective website for designing with ecologically friendly water conservation and ecological concerns.  Moreover, the website offers an interactive online design program to assist in selecting eco-friendly landscape plants.

Additionally, the Florida Native Plant Society offers many resources focused on preserving native ecosystems and plant communities.  Their Education and Outreach webpage makes available an example list of public gardens and natural areas using native plants for landscaping."

Ultimately, green roof design must be approached with consideration for many factors most of us do not consider, such as;

• Native or exotic invasive qualities
• Drought resistance
• Wildlife value
• Fire fuel contributor (high volatile oil content - remember how dry xmas trees burn!)
• the 5 H's and much more.

Green roofs are a popular trend within the green building industry today.  The offer important benefits including;

• Cleaning of nutrients from stormwater runoff (if the roof and stock plants are non-fertilized)
• Providing much needed vertical green habitat to Urban Core wildlife (such as the green Florida anole - which in turn provides superb integrated pest management)
• Creating beauty for people
• Sequestering Carbon and CO2 and providing fresh oxygen as a result of photosynthesis, and more.

We must though, be aware of how we embrace green roofs.  We must take into account all issues, especially those with potential impacts on our ecology and environment. Selecting green roof plant species if a good place to start in designing a Florida Green Roof.

Update on Urban Farm Raised Veggie Beds, Jacksonville Permaculture

Last Photo was Feb 1.  Last month brought little rain but lots of vegetable growth in the raised bed organic soil medium. Watch how the veggies grow.  The first three photos are mid February and the last was taken first week in March.

We are already enjoying our homegrown organic produce and saving a bundle while growing them!

Jacksonville Urban Farm Raised Veggie Beds

Jacksonville Urban Farm Raised Veggie Beds

Jacksonville Urban Farm Raised Veggie Beds

March 2011 Jacksonville Urban Farm Raised Veggie Beds

Green Roofs at Apopka High Career Day - Amazing Ideas from Students

MetroVerde participated in the first annual Apopka, Florida High School Career day with four interactive hour long sessions.

I was quite impressed with Apopka High School's facilities and staff.  ROTC members escorted us guest speakers to our respective rooms.  The school was clean, bright and full of talkative young people.   Ms. Erin Poppert, the Science teacher who was responsible for supervising the Green Roof session ensured I had all the proper audio visual tools needed and participated in each of the four sessions.

Apopka High School

Apopka High School Career Day, Green Roofs

We talked about what green or living roofs were and touched on their benefits;

• possible insulation qualities
• habitat and support for biodiversity
• food production
• stormwater cleansing
• integrated pest management
• beauty - sense of place
• production of oxygen and sequestration of carbon
• and more

Reviewing the 5 H's of Florida Green Roof design principles - 

1. Hurricanes
2. Heat
3. Humidity
4. Hard Freezes
5. High Winds

I could see students - the future scientists, engineers, botanists and entrepreneurs' eyes widen, thinking about the possibilities for economics, environment, health and opportunity.

We discussed rooftop permaculture at length and because we are actively involved in a rooftop permaculture project I thought it would be insightful and useful to solicit their ideas as to what vegetables would be good to grow on a roof.  I know the vegetables I like to use, and know what is drought tolerant and technically feasible to grow.  Sometimes however I find myself caught up in the technical and artistic components of a living roof to the point where I miss the human taste differences issue.

I wanted to find out in a broad, general sense what vegetables the young adults would prefer to grow on a green roof's garden.

• Tomatoes - usually the very first response - most everyone wanted tomatoes!
• Potatoes
• Onions
• Green beans
• Strawberries
• Cucumbers
• Cabbage
• Broccoli
• Carrots
• Lettuce
• Celery
• Peanuts - a very good suggestion (adding peanuts could produce fuel!)
• Blueberries
• Squash - calabasa
• Grapes
• Pumpkins
• Eggplant
• Watermelon
• Peppers
• Raspberries
• Bananas
• Oranges
• Basil
• Rosemary
• Radishes
• Turnips
• Kiwi
• Pineapple
• Corn
• Greens
• Soy beans
• Pinto beans

Interesting!

I will look over the list and learn from it, for understanding people's tastes is an important facet of rooftop permaculture.  Now all the above plants may not work on a green roof.  Many have varying soil requirements and other horticultural needs.  But a comprehensive list of desired vegetables from a broad cross-section of a geographic population is important data.  Understanding the people component to green roofs adds to the potential for long term success.

The Apopka High School day was much fun and I enjoyed the opportunity to interact with creative minds.

Ms. Poppert has fashioned a great science agenda for her students.

I suspect there will be some important future green roof and horticulture research develop as a result of the students inquisitiveness and Erin's efforts.

Florida Biodiversity & Permaculture Green Roof Project - Getting Started, Breaking Ground Contracting

The Green Roof for the Breaking Ground Contracting project in Jacksonville has begun!

Today the roofing contractor will be finishing the edges of the TPO.  Once the edges are sealed and the gutters up the drainage stabilization mat will be attached to the TPO.

The TPO is 80 mil and has a 2" drainage slope from the center towards the east and west edges.

Roof level view of BGC Green Roof Pad

The Breaking Ground Contracting green roof will support rooftop permaculture, native wildflowers and grasses and other endemic species and Florida Friendly Landscaping (drought tolerant) plants.

BGC Walkway to Green Roof, Solar & HVAC to left

Recall wind and light are the two most significant green roof design variables.  We call them primary design variables.  The wind and light summary chart is as follows.

MV GreenRoof Primary Design Variable Chart

Following the design principles we've been discussing here, the wind exposure is primarily from the south.  The following roof grid summarizes wind and light exposure.

BGC Green Roof Primary Design Schematic - Wind & Light Impacts

A green roof and rooftop permaculture mission statement is in development progress and plant layout proceeding based on design parameters.  Follow us as we proceed through the rood assessment into design and then installation.

Feel free to email us with your questions and we are always happy to receive comments.

Green Roofs and Permaculture

Growing food on rooftops is popular in many urban areas.  New York may be leading the way, especially with projects like the Eagle Street Rooftop Farm.

We are working on a Jacksonville, Florida green roof with a significant rooftop permaculture component this spring.

Vegetables are already seeded and many sprouting.  The Dinosaur Kale is about sixteen inches tall and the rocket arugula is growing well also.

We chose the roof area with the most morning sun and afternoon shade for the garden area as roof temperatures climb rapidly during the afternoon.  Though many vegetables, such as the Brassicaceae are considered C4 photosynthesis processing plants and drought tolerant, morning sun and afternoon shade is best.

Here back in the green roof plant nursery we have recently adopted farm fowl on our urban one acre lot.  With several chickens, ducks, geese and a turkey we've had to build enclosures to keep the neighborhood cats, raccoons and hawks from eating our birds.

This weekend we successfully constructed the $50.00 turkey enclosure.  At 200 SF the price per square foot calculates to be approximately twenty five cents per SF - not bad!

Green Roof Turkey House

The turkey castle is roofed with lemongrass, spinach, borage, onions, parsley, cucumbers, cantaloupe and cow peas.

The enclosure is made with simple farm posts, bent electrical conduit and wildlife - bird netting.

The soil media for the green roof is a very lightweight mix of perlite, vermiculite, sand and compost (compost about 50%).  We'll keep the roof fertilized with turkey pellets.

Green Roofs and Permaculture

And as our turkey appears to be a good flyer - I suspect he will be roosting often with the veggies.

Integrating vegetables, fruit and other items such as honey not only provides food for people but also habitat for wildlife.  Increasing the plants insects need increases biodiversity.  Pollinators are an important component of urban core gardening.

Rooftop permaculture - the new frontier for green roofs!

Green Roof & Rooftop permaculture - Economic Opportunity for the Urban Core

One of the components of the new Breaking Ground Contracting green roof will be a working permaculture garden.

Today we will be planting 10,000 yellow onions and garlic cloves for the project.  The cloves and onion sets are already sprouting so within a week the plants should be nice and green for end of month installation.

Garlic cloves for the BGC Green Roof Permaculture Garden & Green Roof

I was peeling apart heads of garlic until midnight last night.  Good time for green roof planting now due to the new moon.

Learning about Native Plants for Living Walls & Green Roofs

Native plants play an important role in supporting worldwide biodiversity heritage.

For a great blog post on just how important native plants are for supporting biodiversity, read the post here at Wildlife Garden.

One of the many ways to learn about native plants is to 'look up'.  This week I spent several hours walking in the moat of the old Spanish Fort in St. Augustine.  In my opinion the National Park Service has it backwards - they charge for going inside the fort but allow you to walk for free in the moat and around the grounds.  The moat is where you can see many, many native and other plants species growing in the coquina walls!

Castillo de San Marco, St. Augustine

As you can see in the above photo, most plants grow underneath the downspouts on the walls.  Though the downspouts provide water primarily when it rains, they also collect dew and fog from surrounding areas and funnel the water to the plants.

Interestingly, learning about green roof and living walls plants from the fort offers insight into those plants that not only do well under the hot Florida sun and with no additional irrigation, but also the plants shed light on soil media composition.

Coquina shell and the limestome mortar have a quite high pH level.  High pH is usually one of the toughest issues to work with on green roofs and living walls.

Samolus valerandi

Pteris vittata & 2 Cuban anoles

Wildlife seeks out plants, especially those providing resource benefit such as food or nectar or shelter.  Native plants are best suited at providing the most optimum level of ecological benefit to those wildlife endemic to an area.

In otherwords, planting native plants on green roofs and living walls encourages and supports native populations of insects, birds, reptiles, amphibians and other wildlife.

Many popular landscape plants used on green roofs may not offer the same level of resource benefit.

Learning about your local native plants broadens design capabilities for both green roofs and living walls.

Limestone & Coquina Walls are Harsh Ecosystems

Green Roof, Southern France from Natural Materials & Native Plant Species

Very excited to share a series of photographs of a green roof in Southern France constructed primarily using natural materials rather than massive amounts of plastic trays and parts.

The basic design was fashioned from the LivingRoofs.org design guide - a great resource for anyone interested in constructing a green roof.  The LivingRoofs.org is, in my opinion, one of the very best resources for green roof design.  Rather than focusing on commercial advertising the LivingRoofs.org site focuses on making available important design data and examples of green roofs from around the world.

The photos here depict in chronological order the basic system approach.

Thorough research into native plants was conducted, inventorying local native plant species according to bloom time, life cycle, biodiversity value, maintenance requirements, water issues and drought tolerant qualities and more.

Interestingly, native reed, Arundo species was used for drainage along with broken and crushed tile, stone, sand and compost.

The reed used is a endemic plant, one used locally for roofs.  Reed roofs have been historically popular in the Mediterranean area and can last as long if not longer than asphalt shingles.  For an interesting review of reeds used for roofing material check out the many websites offering reed roofing products.

This project is particularly significant in the evolution of world-wide green roof technology as it is a strong statement concerning sustainability and biodiversity.

In many aspects our green roof industry has become stale and stagnant.  Most if not all systems today are plastics based, have extremely high carbon footprints with use of petro-kiln expanded inorganics for soil media, use monocultures of one or two plant Genus - most of which are exotic plants not even native to the area.

All this is great for the bank.  But not so good for site ecology.

Today, in my opinion many green roof systems are 'greenwashed' with true sustainability value.

Some say green roofs constructed around monocultures of exotic plants that require regular irrigation and fertilization may be better than asphalt roofs.  However, in my opinion, the forced use of exotic landscape plants on a roof filled with plastic trays is no different than GMO practices - forcing an unnatural product into our environments.

So this green roof in Southern France may have now set the standard for all future truly sustainable green roofs.

Native plants with ethnobotanical and biodiversity value cover the native soil and drainage materials.  The woven geo-synthetic fabric is the only material not found locally in nature - and this could possibly be replaced with hemp fabric or cotton burlap.

When I look at this roof I see the beauty of native and natural materials.  I do not see in black plastics and overused plants.

I can tell you the industry will immediately point to long term life cycling comparisons.  They will argue expanded shale lasts forever whereas green roofs using natural materials will decompose over time.  Big corporate green roof industry will argue that the mats of one or two plant Genus are extremely low maintenance and much better suited for the general population than wildflower populations that may evolve and change with the seasons.

But this roof, designed with ingenuity and a heart for long-term biodiversity and sustainability is greater in significance, in my mind, than the largest turf or sedum roof built in the last decade.

The methods, materials and plant design here now becomes a standard of sustainability for green roofs.

Certainly improvements and adjustments will be developed and implemented.  Yet the statement of a true 'green' roof leaves a lasting impression in my mind.

Enjoy the photos.  For more information contact the designer and builder on twitter - http://twitter.com/toitsverts

Geosynthetic liner

Arundo Reed

Drainage layer - Reed

Crushed tile & reed

Native Plants for Biodiversity & Ethnobotany

Using Native Plants for Green Roof Species

Green Roof Native Plants

Benefits of Green Roofs - Fighting Cancer and Other Diseases

Green roofs and living walls can help clean the air and allow us to breath easier.


Many geographic locations acros the globe have air contaminated with Volatile Organice Compounds also known as VOCs.


Volatile Organic Compounds (VOCs) are chemicals created by industrial pollution and automobile engines among other processes.  VOCs are the primary cause of Urban Smog.  


They are also responsible for the formation of cancers, respiratory problems and other serious health issues.

According to the US EPA, the Health Effects of VOCs include:

Eye, nose, and throat irritation; headaches, loss of coordination, nausea; damage to liver, kidney, and central nervous system. Some organics can cause cancer in animals; some are suspected or known to cause cancer in humans. Key signs or symptoms associated with exposure to VOCs include conjunctival irritation, nose and throat discomfort, headache, allergic skin reaction, dyspnea, declines in serum cholinesterase levels, nausea, emesis, epistaxis, fatigue, dizziness.

The ability of organic chemicals to cause health effects varies greatly from those that are highly toxic, to those with no known health effect. As with other pollutants, the extent and nature of the health effect will depend on many factors including level of exposure and length of time exposed. Eye and respiratory tract irritation, headaches, dizziness, visual disorders, and memory impairment are among the immediate symptoms that some people have experienced soon after exposure to some organics. At present, not much is known about what health effects occur from the levels of organics usually found in homes. Many organic compounds are known to cause cancer in animals; some are suspected of causing, or are known to cause, cancer in humans.

For more health information on VOCs from the EPA click here. 

According to a new study - one confirming what we already know - plants -  - clean these harmful VOCs out of the air.   Read about the study in a National Science Foundation Article here.

This study makes it clear that it is especially important to have as many plants inside your building or home as the levels of VOCs inside a structure can be up to ten times the ambient levels outside.


Plants act as filters for air and rainfall, actually removing and utilizing harmful nitrogen.  They also remove carbon from the atmosphere by using CO2 to produce much needed energy compounds and then plants pump oxygen back into the atmosphere.

As we are bombarded with pollutants each day, in our water and in the air - installing interior living walls, exterior vertical green - green roofs and living walls, Urban Permaculture - City Gardens, wildflowers and trees - can pay off with significant benefits.

Ultimately, we may live longer.  Ultimately, we may beat the odds with cancer or respiratory diseases.

Restoring Volumetric Green to the Urban Core is critical.  Today, go out and plant a seed or a grown plant.  Bring another inside.  Hang plants from your patio walls and your kitchen window.  Keep plants in your home.  Install a green roof.

Green roofs and living walls - cleaning stormwater, creating habitat, providing a sense of place and beauty and - importantly - fighting disease by removing pollutants!

Surround yourself with plants today.  You may breath better and live longer. 


Remember, the benefits of adding volumetric green to the Urban Core include;

• Cleaning Rainfall runoff and stormwater
• Providing wildlife habitat
• Supporting biodiversity
• Creating habitat for endangered plants
• Integrated pest management - supporting pest consuming invertebrates and amphibians
• Noise insulation
• Reducing Heat Island effect
• Creating a Sense of Place and Landscape Beauty
• and more

Wan to learn more?  Email us here.  We will be glad to help you with your next living wall or green roof design project!

Native Plants for Green Roofs and Living Walls - Seeds For Green Roofs

Great Native Plant Photos on the Seeds For Green Roofs website this morning.  Check out the Lamium and Nephrolepis pictures.

Rooftop Permaculture - GMO, Brassica oleracea Root Architecture

"Gene manipulated corn fields feed people"

The above comment was a response this morning to one of my suggestions rooftop permaculture can help.  It is really sad because some truly believe this.

Fortunately - like the present Middle East changing of the old, stale guard and influx of new ideas, I believe rooftop permaculture and vertical permaculture is well on its way to replacing the old and becoming the new frontier in volumetric and rooftop green.

Green Roof Rooftop Permaculture - Brassica

Green Roof Vegetables - Broccoli

The broccoli here were pulled from the roof garden this week.  We had the Brassica growing in 4" of light weight highly organic composted and very well drained soil on a 4/10 slope.  You can see just how the vegetables became with no additional fertilizers and zero pesticides and herbicides.

Unfortunately, large corporations view rooftop permaculture and the citizens taking the task of feeding themselves back into their own hands as a serious threat to profits.

But I reject the above statement that "Gene manipulated corn fields feed people" as the only successful approach.

Many people may want to eat GMO corn products.  Yet I believe a large portion of the population may not want to.

So I see a grassroots movement arising to support rooftop permaculture, one where common people can make nutritional decisions for themselves rather than having the State or a Large Multi-national Corporation do so.

Check out just how big the Brassica grew.  Look at the root architecture.  We planted them close together to brace against wind issues and ate the greens daily. The plants adapted to the 4" soil (100mm) dispelling the myths of need for deep dirt to grow.

ECHO, see http://echonet.org is a great resource for rooftop permaculture practices, tips and design guidelines from a cost-effective approach.

Our $2.00 worth of seeds provided a daily bunch of organic greens and broccoli tops that would have cost US $ 5 in the store for six months.  As I see it the numbers work out to be close to $1000 savings in food costs, not to mention the health benefits.  That is just for organic broccoli alone.  Add the collards, mustards, sugar snap peas, pok choy, turnips, potatoes, tomatoes and the benefit of fresh air and gardening companionship and one can easily see the economic advantage.

No thank you to GMOs and to the outdated, stale industry guru's that are old news.

Green Roof Sedum Plantings

I am fascinated by the Sedum (Hylotelephilum as some botanists suggest).  They are hardy, drought tolerant, can switch between C3 and CAM photosynthesis and several native species provide food for endangered Lepidoptera species including the Grey Chi and San Bruno Elfin Butterfly.

There are many native Sedum species considered native to  the US.  Some are even protected by law as threatened or endangered as in;

• Pennsylvania
• Oregon, and
• Kentucky

Green Roofs have been shown over the long term to provide great opportunity for the re-establishment of endangered species.  Green Roofs may provide an important opportunity for those threatened or endangered Sedum species to recover.

There is a wonderful American Society of Landscape Architects article on the web focusing on a Green Roof with several popular Sedum species as part of green infrastructure installed to help the Rock Creek Watershed.

The Sedum's used in the project were;

• S. sexangulare
• S. album
• S. spurium
• S. rupestre
• S. tectractinum
• S. floriferum
• S. kamtschaticum, and possibly others.

From a habitat, stormwater, 'sense of place' and heat island effect, this project was timely and ecologically important, and so too were the Sedum plantings.

Yet as you will read, many of these species are potentially invasive and have been recorded on state and organization invasive plant lists.

Importantly however, Sedum should not be singled out as the only invasive or potentially invasive plant when discussing green roofs.  There are many potentially invasive plants that could be associated with green roofs.  Last year we posted a brief article on the use of Nandina spp. on the Gainesville, Florida Regional Utilities Green Roof (thankfully the Nandina was subsequently removed from the planting schedule).

Here in Florida, Sedum have difficulty with Southern Blight Fungus and tend to dampen off during the long hot and humid summers.  In Jacksonville, S. reflexum appears to do the best on living roofs though it too suffers from the humidity.

Sedum propagates easily according to botanical literature and others, as suggested in the Emory Knolls Farms website.  In fact, spreading cuttings and clippings of sedum leaves and stems is suggested as a quick approach to filling a green roof with more plants.

However, some Green Roof companies raise a red flag about invasive species, such as S. sarmentosum where as the Roofscapes, Inc site indicates;


"The only Sedum that might be considered invasive is Sedum sarmentosum, also known as Star Sedum,Gold Moss, Stringy Stonecrop, or Graveyard Moss. It has green spearhead-shaped leaves, lemon yellow flowers, and long tendrils. We do not recommend using this species."

But it is not just green roof plant nurseries that promote Sedum's ability to grow into full size plants from the tiniest of cuttings, other ecological or nature websites suggest the same.

An interesting article and discussion of Sedum and Green Roofs can be found on the Taking Place website where the article entitled Sedum2 mentions of S. floriferum (one of the Sedum species used above mentioned watershed project);


 I’m careful to throw the weeded stems away in the garbage, because the tiniest little bit of stem or spare leaf will root in where it lands and start growing.  It’s not a problem (so far) here, because I do maintain my garden; I wonder about pieces of sedum escaping from roof gardens or green roofs, and rooting in, say, along a river bank or in pavement cracks.  It’s attractive, but it can cover and smother other plants if allowed. 

Importantly, S. sarmentosum has been considered an escaped and invasive species in Japan, subject to numerous studies.

Any plant that roots quickly from leaves and stem cuttings could potentially escape a roof.  Birds carry plant material from the roof on a daily basis.  Here in Florida as well as other windy areas, wind is a strong potential vector of plant DNA.  Fern spores are known to have been carried across the Pacific Ocean on winds, introducing Asian ferns to the Americas.

I suggest, planted anywhere Sedums will escape and start to naturalize.  How bad this naturalization will become is another question.

As a plant biologist my own opinion is Sedum will initially only naturalize within the disturbed environments of the Urban Core of cities such as Jacksonville here in the southeastern US, because of the humidity and Southern Blight fungus issues.  I personally believe it will have a hard time becoming established in the Florida swamps.

Not so the case elsewhere.

Here in the US there are many red flags and concerns now being raised concerning Sedum use and the potential for invasive activity.

For example;

• The City of Indianapolis cautions against the use of both S. sarmentosum and S. hispanico in the Indianapolis Stormwater Green Roof Technical Design Manual
• The Invasive Plant Association of Wisconsin lists S. acre and S. purpureum as having invasive qualities
• Missouri's Exotic Pest Plant list includes S. sarmentosum as a category B exotic present in Missouri
• Virginia's Department of Conservation and Recreation ranks S. sarmentosum as an invasive species
• Massachusetts suggests it is necessary to gather additional data on the S. telephium as part of the Managing Invasive Plants program.
• The Great Lakes Indian Fish and Wildlife Commission list Sedum spp. as a terrestrial  invasive
• Wyoming's Natural Diversity Database report lists S. acre as a noxious weed plant located across F.E. Warren Air Force Base
• New York's state Early Detection Invasive Plant Program lists both S. sarmentosum and S. telephium species
• U.S. Fish and Wildlife Service list S. telephium on their invasive plant list
• S. acre, S. albo-roseum, S. purpureum, S. ruprestre and S. sarmentosum are listed as Alien Plants by Illinois' State Museum site
• USDA Forest Services, Non-Native Invasive Plant List lists S. telephinum/ S. purpureum on their Invasive Plant list
• US Natural Resource Conservation Service maps naturalized and escaped non-natives, including Sedum.  Their database of non-native Sedum species occurrences is informative.  They suggest "These plants are introduced to some part of the PLANTS Floristic Area, though they may be native in other parts. While many are harmless or beneficial, others that are not already invasive or noxious have a high potential to become so in all or part of their range. In general, introduced plants are likely to invade or become noxious since they lack co-evolved competitors and natural enemies to control their populations."  Sedum species listed include;
• S. acre
• S. aizoon
• S. album
• S. dasyphyllum
• S. dendroideum
• S. hispanicum
• S. hybridum
• S. kamtschaticum
• S. linare
• S. mexicanum
• S. ochroleucum
• S. praealtum
• S. refluxeum
• S. sarmentosum
• S. sexangulare
• S. spurium
• S. stoloniferum, and 
• S. ternatum

Other Countries too, view Sedum species as an invasive plant, including;

• Poland, New Zealand, Switzerland
• Czech Republic
• Japan - see above
• New South Wales
• British Columbia
• Ontario Society for Ecological Restoration
• Canadian Wildlife Service
• Mediterranean regions
• and many others

Many Not-For-Profit organizations and preserves also consider Sedum to be potentially invasive. A few include;

• Nature Conservancy of Canada - Garry Oaks Ecosystems lists S. acre as an established invasive species
• Wisconsin Botanical Information System tracks county by county where the many different Sedum species have escaped and become naturalized
• Washington State University Extension Blog has a comment " My plant peeve right now is sedum. It's used and promoted extensively for green roofs and rooftop garden use, because it grows so well in extreme conditions -- which makes it also quite willing to grow in not-so-extreme conditions. I planted a handful that a neighbor had given me, and it now has spread through one garden bed, along the base of a rock outcrop on the other side of the yard (I took a snippet and parked it from the bed onto the outcrop, not knowing how it would spread and spread), and now is moving into the lawn. It's easy to pull out, but a tiny piece will root, so composting is out, and vigilant disposal is necessary. I have yet to see sedum on an invasive species list, but predict that it will show up on a bunch of them in the next few years, as pieces make their way off of rooftops and into the on-the-ground landscape. "
• Mid-Atlantic Gardener's Guide says 'Many smaller sedums are invasive..."
• Grassroots websites suggest Illinois' Draft Invasive Plant documents list both S. sarmentosum and S. telephium are invasive
• The New York Botanical Garden's notes S. sexangulare has been newly noted in the Torrey Range as an exotic species

Yet Sedum will continue to be used across Green Roofs here in the US and the World.

The issue is not really about Sedum.

The issue is one of native plants and exotic, introduced landscape plants.

Do we feel comfortable with the practice to replacing native plants with introduced species because the introduced species are easier to use, hardier and more resilient (maybe because of the lack of natural predators)?

I believe Sedum can be managed appropriately on Green Roofs.  Rooftop growing areas can provide habitat for those native Sedum too, offering protection for those endemic plant species threatened by monoculture takeover of exotics.

The key component to successful exotic Sedum usage is awareness of its plant biology, maintenance practices, local exotic and invasive species management plants, state and federal laws and proper coordination with state and local Native Plant and Invasive Plant organizations.

Many of the lists above are not law.  Sedum is not illegal to use.

The lists above caution us to take account of our practices.

Changing the constituency of Nature can be a dangerous act.

Modeling Green Roof & Rooftop Permaculture Plant Design Performance

As previously stated, light and wind appear to be the primary design variables impacting green roofs and rooftop permaculture.


Understanding how your rooftop garden or green roof plants - vegetables, native plants or other - are impacted by light and wind is very important.


Recall from previous posts, discussions about identification and boundary delineation of  roof areas according to levels of available light and present wind loadings.  The roof under consideration was sectioned off on a five meter grid and assigned design levels of wind and light influence according to the following simplified diagram.  Light and wind can be considered the two primary design factors.

Green Roof Design Diagram

This is not to say the secondary design variables are not important, as they are.  Secondary green roof design variables include:

• Climate and Weather
• Rainfall
• Non-Rainfall Air Water Vapor and Humidity
• Dew, Types of Fog and Frost
• Smog
• Temperatures
• Adjacent vegetation
• Nearby Allopathic Plants
• Adjacent Exotic Invasive Species, and
• Local Seed Source

Though not used to determine the roof polygon boundaries, the secondary variables play an important role within a design model considerations and we will discuss those interactions in detail in future sections. 

Importantly, certain light wavelengths are required for photosynthesis.  Without light photosynthesis does not occur and plants do not grow.  Light is the first primary design variable to be considered when creating roof ecosystem polygons.

Wind is the second of the primary design factors used to determine roof ecosystem polygons.
  

Though ambient outside air temperatures, precipitation, air quality and other design variables are generally consistent across the roof, light availability and wind effects can change depending upon where one stands on the same roof.  Both light and wind are critical factors in designing a green roof for dry and arid climates.  Without adequate light plants will not live and consistently buffeted by desiccating winds plants may cease to transpire and quickly die.


Understanding how wind and light impact the green roof can afford the designer the capability to predict plant growing success.


The following diagram suggests that the optimal growing space on green roofs and for rooftop permaculture lay in areas with moderate to strong sunlight and still to slightly moderate winds.

Green Roof Design Diagram

Finally, understanding the light and wind levels across the roof under consideration can help avoid so-called 'dead-zones'.


Dead zones are areas on the green roof subject to light and wind conditions beyond suitable for most C3 and C4 plants.


CAM and other hardy succulent plants are those most desired for roof areas identified as harsh, a result of too much light and/or too much wind.


Know your wind and light levels.


Your green roof plants will grow accordingly.