Planting the green roof. What is a native plant, really?

Many folk have an opinion as to what a native plant is.

As a botanist and a lawyer by education, I typically use Aristotelian logic/reasoning to satisfy myself when answering a question.  My world view is centered around the classical world.  But I am trying to shake that up a bit.

Get rid of the thugs, a comment Ive read on this website has stuck in my mind and I cant seem to shake the thought.  Surely there is nothing in this statement I can rest an argument for defining a native plant on, so why I ask myself, does it keep ringing in my mind.

Earlier this summer I was asked to team on the design of four green roofs in Bermuda, with of course the caveat being the plants I chose should be native plants.  The island is volcanic and all plants are introduced, many the same species I work with along the eastern coast of the U.S.  I could use the logical definition, a Bermuda native plant is a species living on the island before humans arrived.  A native plant must be one deposited in the local terra firma by Mother Nature.  But as I reviewed what was on the island and all the available historical records, such as Nathaniel Lord Brittons 1918 treatise entitled Flora of Bermuda, bewilderment set in.

The whole cross pollination and hybridization issue confused me.  There have been a lot of plants brought onto the island over the last hundred years by humans and no one seems really sure what plants were on the island before record keeping became common place.

Once I started considering the nativar and genotype issues I really became concerned there would be no answer satisfactory to my above mentioned logic training as to what was a Bermudian native plant.

Could a human introduced plant be a native plant?  Maybe one carried on a raft like the Kon-Tiki as a food or ethnobotanical resource thousands of years ago?  Or are plants introduced by humans non-native?  In ten thousand years will Brazilian Pepper be considered native in Florida?

But maybe the issue was really one about invasive plants and not necessarily native status?

Now I was really going nowhere.  While some native plant enthusiasts analyze in minute detail genotype issues I daily fight the U.S Department of Interiors recognition that sedum is a native, along with much of the entire green roof industry players who take delight in emailing me of sedums non-invasive and adapted qualities and asking me why I am hurting a fledging green roof plant industry.

Watching acres of green roof sedum planted across North America each year makes me wonder if the majority of our neighbors and our municipal bureaucrats buying the sedum roofs dont really care about native plants, much less hybrids and cultivars.

Having a background in Florida ecology Ive watched the talking heads for years do more harm to global gopher tortoise populations because of their arguments against relocation due to contamination of the gene pool.  Many times a population was permitted to be destroyed rather than moved to cross-breed with tortoises several hundred miles away.  I honestly became disgusted with the narrow and fundamental-like focus.  Chalk it all up to our cultures adoption Aristotelean logic.  There must be a right and a wrong, a black and a white.  There is no correct shade of grey.

On the left hand are the crazies who want to import any and all and do monoculture, driven by capitalistic opportunity.  On the right are the talking heads who make the whole invasive, exotic, native plant definition out to be a seemingly impossible to resolve genotype issue, quickly to be left behind (except by the talking heads) as society really doesnt give an educated hoot.

Deciding what green roof suitable native plants to use in Bermuda was not getting any easier.

But the the thug statement kept ringing in my ears.

Obviously I dont want any thugs on the green roof.  So I decided to start by eliminating any thugs.  Native plants can be thugs too, like the willow and typha here in Florida.

After eliminating the thugs, the 10-20-30 rule I carry around everywhere turned out to be useful.

No thugs and no monocultures.  If you arent familiar with my version of higher taxa biodiversity through the 10-20-30 rule the explanation can be found here.

If you ask someone off the street what, in their opinion, is a native plant youd get many different answers.  Of course, within Aristotelean framework, opinions are not acceptable usually for basing a logical explanation upon.

Many in the world today, especially the green roof world, including the U.S. Department of Interior, consider sedum to be native.  If the government says a plant is a native does the plant then become a native?

Thank goodness I didnt have to consider endemicity for the project.

So I ended up steering away from all thuggin species (thanks Ursula!).  And made sure the roof would contain no more than ten percent of any one species, no more than twenty percent of all the plants being of any one genus and no more than thirty percent of the total plants chosen coming from any one family (sorry Asteraceae :) ).

Of course I need my CAM and C4 plants since the roof is nature irrigated only.

No thugs, 10-20-30 rule, CAM and C4 plants and I added the qualifiers that the plant could not be an obvious out of place landscape plant (though no good definition exists for such) and the plants must be grown from seed or cuttings of plants presently growing in a five mile radius, harvested in accordance with law and good judgment.

Laughingly, I decided the above specifications could meet the non-Aristotelean logical definition of a native plant.  And truly, there are other forms of logic existing in the world.  Who is to say Traditional logic is better than contradictory approaches?

And most important of all, the green roof is going to survive and grow without added irrigation or fertilizers, contribute to biodiversity, offer beauty, clean stormwater, sequester carbon, produce oxygen and create an integrated pest management system.

The perennial peanut and sedum mono-culture advocates are left out.

The syllogistic talking heads are still analyzing.

But the green roof design is completed and soon to be built.

And Ive decided situational logic is perfectly consistent with true logic.

Now, how do I convince the U.S. Department of Interior to get rid of their monoculture sedum green roof and plant natives instead?

 

 

 

© 2011, Kevin Songer. All rights reserved. This article is the property of Native Plants and Wildlife Gardens. If you are reading this at another site, please report that to us

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    About Kevin Songer

    Kevin and his wife Judy run MetroVerde, a plant-based biodiversity business.  Their focus is restoring wildlife habitat to the urban core, 'volumetric green' as he refers to the vertical landscaping.  Kevin's undergrad is in biology with a focus in botany and he holds the Juris Doctor in law (environmental and land use).  He worked for the USFWS while in law school on Endangered Species Act lawsuit data.

    MetroVerde's green roofs and living walls are designed for cyclone and hurricane impacted areas and designs center around native plants.  MetroVerde was awarded the North Florida USGBC's award for Innovation in Water Conservation and Landscape Design for the Villa Paraiso project.

    Kevin writes a daily green roof blog, Living Green Roofs and Seeds For Green Roofs. He is a LEED BG+C and an ISA Certified Arborist & Municipal Specialist Arborist. Follow @kevinsonger on twitter

    Comments

    1. Beatriz Moisset says:

      I applaud your work with green roofs. I would like to see more around here. Thanks for another great article.
      I understand your dilemma. When an ecosystem has been as severely modified as the one you describe, it may become impossible to find a balanced combination of natives that are easy to grow and do well under the circumstances. I think that, if the 100% natives goal has become impossible, the best option is more natives than in the surrounding area. This seems like a sensible compromise.
      I see the same dilemma when trying to create lawns for pollinators, by allowing a variety of broad leaved weeds or flowering small plants. Many of these grass companions are not native. But, then again, so are most grasses. So it is better to add some of them, native or not, to the almost monoculture of a perfectly manicured lawn. Of course, the best solution would be a wildflower meadow, but that goal is sometimes unattainable.
      Beatriz Moisset recently posted..Bees and vitamins

      Reply
      • Kevin Songer says:

        Beatriz you are so right about the monoculture problem. Nature never creates monocultures thank you for the encouragement and words of common sense.

        Reply
    2. Sue Sweeney says:

      Great minds ponder the same subject. Id be interested in your comments on my last two posts:

      The Nativar Dilemma http://nativeplantwildlifegarden.com/the-nativar-dilemma/

      Defining Native and Invasive http://nativeplantwildlifegarden.com/defining-native-and-invasive-2/

      and Vincent Visacheros similar posts

      Reply
      • Kevin Songer says:

        Sue I read yours and Vincent Visacheros posts. Your differentiation between the Urban Core and Suburbs is insightful and I agree. I also applaude your suspicion of nativars. Nativars are sometimes only a step away from exotics then invasives. In fact, I would go on to say that most any native plant purchased in a nursery is more an exotic than a native. The traditional reasoning holds that if mankind has brought a plant into an area it is exotic. For example, the native azaleas or native pitcher plants readily found on Floridas west coast can be found sold here in Jax as natives. Yes they are native to Florida, but they are really an exotic here in Jax. To me, except in pristine forests of the world, there are few natives left.

        But the plants that have longstanding history with an area, those that were here before the Americas were colonized by the Europeans are the plants I tend to gravitate to for use on the green roofs.

        I am attracted to those plants, and I call them natives for several reasons including;

        1. They exhibit higher survival rates on the harsh roof environment than most others,
        2. They attract magnitudes more pollinators than any other species this is so important to my food plants on the roof. On test roofs the food production has increased over one thousand percent when native wildflowers and weeds are planted alongside food over those roofs with only food plants or food plants and exotic landscape plants.
        3. They provide more unique beauty (this one is subjective and my opinion).
        4. Natives are reliable.

        I do not use native cultivars and I usually use only those cuttings or seeds that I have had for many plant generations. Judy and I have been growing native plants for many, many years.

        Maybe insects and wildlife are easier to define as being native or non-native. I suspect they do not hybridize quite as easily as plants though I am not a zoologist. But watching the native pollinators and smaller amphibians and reptiles that visit the roof, the native species make their way first on the green roof to the native plants and weed section, spending most of their time there.

        I attribute the massive amounts of pollinators and wildlife on our green roofs to the native plants we have growing there.

        I attribute the massive amounts of food we harvest from the green roofs to the native plants growing side by side with the food plants.

        For the Urban Core this is good. Green roofs provide a bit of green jungle to an otherwise black asphalt jungle.

        I think all is fair in the Urban Core as long as monocultures and invasives are avoided. Your point about the suburbs deserves listening to.

        Im now pondering native food plants. Though I love my peppers and tomatoes and beans on the roof, maybe it is time for me to learn about native foods. Surely there are many benefits to learning about growing food plants that historically have been considered native. Here they would be Guadalupe cucumber, yucca, cattails, grapes, and many others.

        I have made the change in my diet over the years to a beans and rice based diet but maybe now is the time to learn how to eat native plants.

        Native food plants do make a really interesting addition to any green roof. They are also almost as indestructible as native wildflowers and so much more drought tolerant than typical garden vegetables.

        And some exotic food plants can really become invasive too!

        I dont think I would ever go hungry switching to a native food plant focus. The Seminole pumpkin in my backyard covers 1/4 acre and has fruit all over it right now.

        Thank you for your comments and posts Sue. You have succeeded in raising more interesting thoughts for me to lay awake at night and think about, without having to ever come to an answer.

        Reply
    3. Kathy @nativegardener says:

      Kevin, I want to applaud the good work you do. The situation in Bermuda being volcanic rock is certainly interesting to hear about. It is good you put much thought & research into the solution. Native plants are always the best, of course, but on the roof I think the bottom line is as you said:

      And most important of all, the green roof is going to survive and grow without added irrigation or fertilizers, contribute to biodiversity, offer beauty, clean storm water, sequester carbon, produce oxygen and create an integrated pest management system.
      Kathy @nativegardener recently posted..In the News: Native Plants Deserve a Spot in Our Landscape

      Reply
      • Kevin Songer says:

        Kathy,

        Thank you for the comments. Native plants do deserve the spot in the landscape as you point out. I love your blog and I am extremely envious of your knowledge of cactus, sage and succulents for it is these plants with C4 and CAM photosynthesis processes that I use as wind breaks on our green roofs. They are the hardiest of the hardy.

        I followed your blog signed up looking forward to your posts.

        Kevin

        Reply
    4. Jorg Breuning says:

      Great article and I really appreciate that people are questioning more and more some of the ridiculous discussion about natives fueled by so called environmentalists or by bureaucrats that just picked a job in the environmental field because it is chic. In many cases these people are the same people that promote farming, hydroponics or other obscure ideas for extensive green roofs as environmentally friendly solutions. They don’t know how to do these things on the ground but they do claim they can do it on a roof. It is interesting that people focus on native plant discussions for green roofs that are no existent when you compare the green roof areas with man-made Parks, farmland, front or back yards where native ground/soil offers a completely different performance.

      The American or English-spoken green roof market for modern green roof technology is around 10 years old. So, the biggest problem is that all called or self- nominated green roof experts in Northern America are typically gained their professional experience in fields that are completely different of what might be helpful for the green roof technology or the native discussion. Geologists, mechanics, metal workers, farmers, nursery men, sales reps, lawyers or roofers representing the American green roof industry and try to gain experience on roofs of others that are actually paying for the “testing”. I already saw so many people and roofs literally coming and going and we are not at the tip of the iceberg yet. In 10 years from now I expect well-trained, next-generation green roof experts. Once these people are in key positions they will bring this discussion to a point where sense and simplicity finally takes over.
      Starting to “rule” nature with 10-20-30 rules seems even weirder and demonstrates that former experiences in another profession might not always be helpful when it comes to nature. Some former experiences are more helpful for promoting than for executing.

      For example if one plant out of the 10-20-30 assortment finds better than perfect conditions it likely out competes others without asking for specie, genus or family. Not always it makes sense starting something that most likely will not sustain or is impossible to maintain – beside the visual aspect. Environmental conditions are different every day and over the last hundreds of years even when you stay in the same location. Environmental conditions can be even more divers on ground remote location like roofs where everything, from exposure to a leak in the roof can offer advantages or disadvantages for a certain plant.
      However I believe that people will soon learn again the lesson that you cannot rule nature actually the nature laws are the rules we depend on. Modern green roof technology and all environmental technologies with living components is all about working together with nature not ruling it. We have to support nature with professional respect, courtesy and common sense.

      Since you cant get rid of people in environments where they haven’t been before the native discussion is already buried alive. “Invasive” should be the discussion.

      Reply
    5. Sue Sweeney says:

      Jorg your designs are actually quite visually nice and may be you do know a lot about the roof environment. For roofs and other elevated structures, is your end goal sustaining local native wildlife or something else? I suspect the latter.

      I work on the ground with the end goal of sustaining local wildlife and I assure you that, there, what is native is very, very important so that we can help nature (as you call it) heal the gaps in the ecological circle. BTW: how my team does it: We support nature with professional respect, courtesy and common sense. I guess we have at least that in common.

      Sue

      Reply
    6. Kevin Songer says:

      Jorg;

      Thank you for your comments. As I have said before, the world admires your long-standing green roof work. You have been involved in European and American green roofs for longer than most and you are to be recognized as an expert.

      I also appreciate you understanding the English language and your ability to study green roof work in many other languages. Unfortunately many have not made the effort to become multilingual and can only read about Germany and Italys and Europes green roofs through google translator. :)

      Most native plant people here in America are not involved with native plants because it is chic, they are involved with native plants because of a passion to understand nature. Here native plant people are referred to most commonly as nerds not chic. I would again remind you I have never been a banker or a baker or a car salesman. As you I have been a dirty fingernail gardener all my life.

      But the dirty fingernails is about all we share in common. I cannot reconcile nature as you speak of her with your monoculture sedum or sod roofs from your expansive Italian sod farms (even with thos few grasses you throw in). And when you speak of not understanding biodiversity at higher taxa (10-20-30 rule) perhaps this is because the old school industry of monoculture green roofs and sedum roofs must feel financially threatened by native plant enthusiasts wanting to support local wildlife biodiversity through the replacement of boring sedum with exciting (and chic) native wildflowers!

      Of course you will never totally agree with me. I honor your perspective because you are old school and have laid extensive, though somewhat mis-guided groundwork.

      Your name and style is renown. But as I said in my article, traditional logic such as syllogism was based on the assumption everything there is to know is already known and this is how I view old school monoculture thought. Fortunately the industry is making a clear break from all sedum roofs and all sod roofs. The old school had its chance but is dying out as a failed experiment.

      Your work was good in its time and though your roofs are so beautiful, they are not what mother nature would design. Mother nature is more rigorous than the 10-20-30 rule. Take a walk in the forest. Draw an imaginary 20 meter by 20 meter square across the ground, the size of a small green roof. Identify each plant by family, genus and species. You will find mother natures rule is magnitudes more complex than the 10-20-30 guidelines. You will never find a sedum or sod stretch in nature here as on your roofs.

      In fact, your sedum plants are escaping across the cities and urban core of the Americas becoming feral sedum, creeping silently down cracks and crevices of sidewalks and parking lots, growing everywhere, poised to take over! Many municipalities are now taking notice at this exotic invasive the old school has overused. Check out my blog for more info here on the old school sedums invasive species lists now in existence. http://kevinsonger.blogspot.com/2011/03/green-roof-sedum-plantings.html

      You are such a good sport too! I am still trying to find a chic native plant person who was a banker in a previous career. Let me know if you spot one first.

      Kevin

      Reply
      • Sue Sweeney says:

        well, actually, now that the subject has come up, I was in financial services 1980 thru 1998. However, Im not that chic unless you really like honestly dirty blue jeans.

        Reply
        • Kevin Songer says:

          Sue, dirty jeans are awesome as are native plants. One of my favorite native banker plants here in Florida is the hated $$$ Weed, Hydrocotyle.

          I so admire this evergreen plant on my green roofs

          She has been shown to remove more nitrogen from water than most any other plant. Hundreds of times more effective at cleaning stormwater than the S plant.

          Reply
    7. Ruth Parnall says:

      Kevin -

      Setting the definition of native aside, your approach to planting for green roofs seems very workable, sensible, and would probably fit one of my measuring sticks: Do no harm. Sounds as if your designs go way beyond the conventional by considering wildlife habitat and food production. I admire your efforts to Know the territory (another of my measuring sticks).

      On the issue of green roofs in general, I think designers and suppliers (you excepted) must not be fully understanding the specs from Europe which seem to be primarily for stormwater management, and may be why sedum is so popular. Most US communities are basically unconcerned about site runoff. Portland, OR may be the big exception in wanting to give runoff every chance to absorb into the ground, and the arid states and Carribean islands wanting to create chances to collect runoff for re-use.

      Im guessing that many green roofs here are motivated mainly by aestheticsa better view from ones hi-rise window. I should think that passive cooling for the rooms under the roof, for glare into windows above the roof, and for moderating the temperature above a city would have become important but seems not to be seriously considered. Otherwise, why would Mayor Bloomberg in NYC be an advocate for the white roof movementpainting roofs white, and reflecting all that heat back into the air (and of course contributing nothing to habitat improvement or food production).

      Reply
      • Kevin Songer says:

        :) Ruth white roof are sooo much less expensive than vegetative roofs. And they reflect all the solar gain back up into the sky, keeping the cities cooler!

        But within a year most white roofs have turned grey from dust and soon become black. However they can be washed back to white (bleached?)

        But the big advantage living roofs offer is the habitat and biodiversity value. So totally amazing how much wildlife comes.

        I love living roofs so much. Even perennial peanut and sedum roofs are soooo much better than black asphalt roofs.

        But native wildflower roofs and prairie grass roofs are the best hands down, running circles around silly sedum.

        Thank you for your comment!

        Reply
    8. UrsulaV says:

      *grin* Hey, glad to help in any small way! Down with thugs!
      UrsulaV recently posted..And now, a random moment with pollinator…

      Reply
      • Kevin Songer says:

        Zinnias are sooooo awesome, and a magnificent green roof plant. So is the pollinator!

        Reply
    9. Jörg Breuning says:

      In my statements it is not like it is in American politics: if you are against Republicans you must be a Democrat…
      I am not a Republican and I am not a Democrat. I introduced to the US not only Sedum Green Roofs – Sedum roofs that’s what the locals found as they google-translated some German literature (which is hardly available online). Aside with the Sedums I also introduced diversity and to convince one of the big shots with growing green roof plants it took me forever, on a daily bases as I helped him to start his company and his first book. It is all about diversity – I can just repeat it: is all about diversity. I never stated something else. Again I am the person that introduces diversity in the beginning of the green roof industry on many projects including the City Hall of Chicago (known as the first American green roof according modern green roof technology). I know I might repeat myself but I am not republican or democrat, not black or white, not yes or no – I am like nature, all colors with all shades (I simply blend in, like everybody would do if taken the shades away).
      To make my position as clear as possible:
      Growing native plants on extensive green roofs is almost impossible because the extensive environment is not a native environment in most location. To support native plants on roofs the set-up must completely chanced (e.g. Swampland for NYC) to a heavy high maintenance intensive system. This is so costly that green roofs would not be feasible because the environmental benefit- cost ratio is for intensive green roofs extremely bad. Doing and native environment on the ground would cost only a fraction AND on the ground it has all the necessary players that are essential to “maintain” everything. It has all animals including mosquitos, ticks, deer, raccoon, and bears or alligator. As a native expert you just cannot fade-out what you don’t like. Doing a native environment according a “rule” on the roof is fading-out things – whatever your criteria are.
      I don’t believe – I actually know that more than a billion sq.ft extensive green roofs are projected for the next 5-8 years. I am fighting for diversity on each of them. Diversity = other plants that Sedum that can still sustain under these extreme conditions. Some of them might be native in certain areas.
      Diversity on extensive green roofs is very important to support the growth and health of the Sedums that are the base plant to make the system work at any day of the year and that make sure everything stays in place for ever. This diversity also supports certain animals and plants to utilize extensive green roofs as a stepping stone to a hopefully new native environment. Extensive and divers extensive green roofs shall be also an important, affordable and highly efficient bridge to connect a native network throughout North America.
      For the cost of one square foot of native green roof you can construct probably more than 100 sft of native environment on the ground – if you get rid of the “Urban Sprawl” – Urban Sprawl is the #1 enemy of native environments and environmentalist. Because it is so difficult to fight against Urban Sprawl people look for alternative places than the ground and that is what makes me upset. Somebody must fight the battle on the ground – I focus green roofs since 1980 and I have a system in place that already supports the battle on the ground. Why reinventing?

      Reply
      • Kevin Songer says:

        Jorg

        With all your green roofs you have done more good for the urban core than most others have ever dreamed of. Kudos many times over.

        Yet why did you choose an exotic, alien, boring plant like sedum though?

        Native wildflowers are so much better suited here in the states!

        Natives are not reinventing the wheel. Just fixing a bad flat sedum and peanut tire.

        PS I really admire your complex multi-lingual ability and am honestly a bit envious. English is such a monoculture like sedum is.

        Though I speak spanish having grown up in Hialeah..

        “Son las mas Santos en el monte que en el cielo.” El monte is the forest of plants as Lydia Cabrera was referring to in her book Yoruban/Igbo/Fina book El Monte plant ecosystem being a complex interaction of divergent species coming together to form a perfectly functioning whole.

        I look forward to your valued perspective on green roofs because you have done this for longer than most.

        Thank you,

        kevin

        Reply
    10. Jörg Breuning says:

      By the way lichen flora, mosses, prairie land etc, etc are wast divers mono-cultures.
      Even the sand in the dessert has a diverse monoculture called bio crust with blue-green algae.
      Freshly eroded areas start with mono-cultures, too. Our design allows only a limited succession as you find in nature in many areas in the US and around the world.
      jbi

      Reply
      • Kevin Songer says:

        Jorg

        Thank you for the comments you challenge me constantly to think outside my comfort zone. I surely appreciate this though I disagree with you on a few minor points.

        There, Jorg, is no monoculture in nature (at least in North America!)

        Sorry.

        Nature abhors monocultures. Read this great article http://www.frontporchrepublic.com/2009/03/against-monoculture/

        Reply
    11. Jorg Breuning says:

      Kevin,
      Not sure whether I was really clear.
      1. I am not promoting Sedum monoculture.
      2. I am talking about divers monoculture in nature (this is a habit caused selection of plants).
      3. I am promoting a highly efficient living machine that can be easily implemented on almost every flat roof at affordable cost with extremely low maintenance (= max benefit for the environment).
      4. less than 50% of the articles and information on the web is true. I leave it up to you to believe me and I leave up to to believe me.
      5. I am challenging you and people because this is the most efficient way to educate when I see a deficit.

      Please re-read the four bulletin points again to make sure you understand my positions

      Reply
    12. Sue Sweeney says:

      Jorg and Kevin Question for you both, if you know. I greatly enjoy the NYC High Line, despite the gratuitous use of Id say about 10% non-native plants, which so detracts from the public education message that we need to send.

      What truly bothers me about it, though, is that I see very few insects or insect damage, and almost no birds. At first, I thought this was due to a lack of water but it hasnt improved much after the water features went in. Any ideas why?

      Reply
    13. Jörg Breuning says:

      Sue,
      NCY has tremendously changed by human intervention. Most of the former swampland of the city along the water fronts is reclaimed land. Away from the waterfronts it was a wild forest – still samples at the botanical garden of New York – in the Bronx. None of these environments I can find on Highline. It seems the native discussion is something where people have many different pictures in mind but not much common sense. Getting attention seems more important than the intent.
      As I said before on any ground remote projects it is very difficult to get ALL native players together. The smaller the area or the more remote the habit, the more difficult – and the more questionable whether it is worth the effort.
      The problem is the design intent. In a native environment you don’t necessarily want to have humans because they are not part of it and they literally keep other native players away by selection (“shoot the female deer because we have too much damage”). There is no combination. Either you design native environment or something for people. Central Park is something designed for people and it is well known for the high density of species (migrating and resident). Obviously habitat designed for humans can bring an unbelievable diversity – not necessarily native though but the combined benefit for both nature and human seem much bigger to me. Especially in a city where green is very important.
      On the Bronx Court House –standard extensive green roof – hardly any maintenance in the last 6 years and no irrigation. It simply is a Jörg Breuning (German) style, divers Sedum roof that currently is being used in a larger study of NYC green roofs, where both birds and arthropods present are being recorded.
      They say: “To date, multiple bird and insect species have been observed on the Bronx County green roof including northern mockingbirds, chimney swifts, goldfinch, and even a ruby-throated hummingbird. Surprisingly, soil and ground dwelling arthropods are some of the most common arthropod species collected, but various bees, butterflies, and crickets are always present.”
      We are talking about a 90% of the area as a 4 inch extensive green roof simply done as I did millions of square feet before and as efficient and cost effective as possible. However we have only occasionally human traffic up there.
      I avoid designing an egg-laying-wool-milk-pig. Having a clear design intent and keeping things simple benefits all. In cities it is all about the people and this needs to be served. Big and dense cities help to reduce Urban Sprawl (see other post) and help to protect native habitats.

      sorry for the long post this is the last one on this blog please email when looking for more

      Reply
    14. Kevin Songer says:

      Jorg you dont have to stop typing here this is very educational what you are saying. I think all those reading would enjoy your thoughts continued.

      I am going to respond also when I have a few minutes to write. I agree in part with Jorg though natives are used the ones used are not the weedy species but more later this afternoon.

      Jorg, by the way we have very successful extensive green roofs growing without added irrigation in 30mm of soil and less, and they have survived for years. The trick? We use native plants.

      Finally, the sedum divers is still an exotic species. It never will be a native. But the US government considers sedum a native so I guess they really have created an egg-laying-wool-sedum-native

      :)

      Reply
      • Loret says:

        Kevin, when you say sedum, is there a specific species you refer to?

        I looked up at the USDA plants database and find that they only consider certain species of sedum to be native in specific areas of the country:

        looks like those with considerable native coverage would be Sedum ternatum in the east and Sedum lanceolatum in the west, and then a few species sprinkled here and there as being native in certain states. I recall having sedum in my NY garden, tho am clueless as to the species it might have been. None of those listed in the USDA database are considered native to FL (now my home) so for me it would be a moot point (only natives, moving forward, for this gal).

        http://plants.usda.gov/java/profile?symbol=SEDUM
        Loret recently posted..The Sulphur Butterfly Emerged Already!

        Reply
    15. Kevin Songer says:

      Jorg:

      I dont use all natives either I need to say this so I am not appearing to be a hypocrite. I use lots of exotic food plants and lots of exotic flowers.. But the natives are always present and I believe they are key to my success.

      But what I just cant let go of is people just dont seem to care sedum is not a native Its just a principle. We should just go ahead and say this green roof is sedum, an exotic species. Then Id be happy If it even matters

      Thank you very much for your insight as always.

      Kevin

      Reply
    16. Kevin Songer says:

      Someone should go throw some Bidens seed bombs on the High Line I suspect it may be there now but it wasnt on the planting list. Add more weedy natives to provide habitat the High Line needs intense shelter and rugged, habitat not just nectar sources

      Reply
    17. Gloria says:

      This is a very interesting but confusing. Sedum alone or any plant for that matter can not be expected to create a functioning self sustaining system. So green roof people must find a workable community that fits into the surrounding community (rain fall, temperature scale, near the sea or inland,insects birds,etc.) and the specific conditions of the roof (exposed,wind,full sun,weight allowed etc.)
      Wayne Tyson says that a successful project (talking about restoration communities)is defined by sustainability , low invasibility ,productivity ,nutrient retention and biotic interactions. And that resetting basic conditions help natural systems recover lost or interruped functions faster.

      So using dominate native plants from similarly exposed disturbed regional sites, to set the stage so to speak,not necessarily using the natives that grew down below a couple hundred years ago but what grows on local dunes, barrens, recovering industrial-military sites or whatever communities applies to a particular roof,could be a place to start?
      Gloria recently posted..Harvesting seed.

      Reply

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