Potential green roof plants

[GreenRoofer]

Stipa hymenoides looks very promising. Already growing the Bouteloua gracilis, which I affectionately call eyebrow grass due to the seed head. Also growing Schyzachyrium scoparium, Bouteloua curtipendula, Koeleria cristata, and Panicum virgatum.

[cohan]

Some of us are fans of Sedum here! I started some basic rock gardening in my teens, and had started growing cacti and succulents indoors just before that, so my first plant loves are succulents, and any succulents that can be grown outdoors in this cold climate are exciting to me, including Sedums, both common mat forming species and less grown small clumpers. I only have a few now, but hope to expand that number over time!
I'm sure the bulk of people who will be using buildings with green rooves, appreciate a more lush (taller) vegetation, but personally I love areas that have low plants only longterm. Although trees/shrubs can be wonderful for shade and form, I know when I lived in the city, the most exciting thing to me was any space where I could see/feel the sun and have a clear view for more than a few metres!

[Lori S.]

I'd wager too that most people here are growing a variety of Sedums...   The more commonly-grown species may not always feature largely in the "to die for" alpine plant discussions, but just browse around a bit (e.g. the "What do you see on you garden walks" threads) or go to main page and the plug the word "sedum" into the search function.  

Great discussion on green roofs!  Thanks, GreenRoofer!

[RickR]

A lot of people villify Sedums, even on here....

I would like for NARGS as a whole to view Sedums more favorably, I know they're 'too easy', but they can act as a placeholder for more slow to establish species. And in flower, they can be stunning as a mass.

When I mentioned that my friends "resolved to have no Sedum or Sempervivum spp." on their shed roof, I didn't mean they didn't like them.   They grow many sedums in their gardens and numerous troughs.  I think they wanted to prove that they weren't a necessary components on a green roof.  Thirty years ago when they built it, I believe this was a prevailing notion.  I am sorry to have mislead you, if this is where you got the idea that NARGS looks down on sedums. 

As rock gardeners, we just use sedums differently from your green roof ecology theory.  While alpine and green roof ecologies do intersect, obviously, they are not the same.  I grow seven sedum species, myself.  Likewise, grasses certainly are beautiful on a green roof, but I erroneously assumed you were asking for alpine compatible materials.  My apologies, then, for my past comments on same.

[Hoy]

In Norway green roof usually means turf on the roof. Turf has been used in millenia although it fell out of use last century. Now it is increasingly popular, especially on cabins:
http://www.google.no/search?q=torvtak&hl=no&client=firefox-a&hs=vaN&tbo=d&rls=org.mozilla:nb-NO:official&source=lnms&tbm=isch&sa=X&ei=PpoDUYi8J5L14QTgtIAg&ved=0CAoQ_AUoAA&biw=1280&bih=666

Although grass is the predominant type of plants, other kind of plants are used too:
http://www.google.no/search?q=gr%C3%B8nne+tak&hl=no&client=firefox-a&hs=9w2&tbo=d&rls=org.mozilla:nb-NO:official&source=lnms&tbm=isch&sa=X&ei=opoDUa-HNoiL4gSgzoDAAw&ved=0CAoQ_AUoAA&biw=1280&bih=666

Here is my version:

[Tim Ingram]

It's great how this Forum stimulates new ideas. This brick shed in our garden has been enveloped in wisteria and covered by the neighbour's leyland cypress for years and needs renovation! We were simply going to re-roof it, but now it's obvious that we should plant it as a 'green roof', even if on slightly smaller a scale than discussed earlier. It won't be able to carry the weight of Trond's cabin (!) and tallish, drought tolerant species would be necessary to show up well - grasses, irises, maybe annuals like Omphalodes linifolia. Will be an interesting project and I am very grateful that this thread got started.

[RickR]

Forgot to mention about our Chapter banquet with Ed Snodgrass:

Each table had a centerpiece that doubled as a doorprize.  We made little 8 x 8 inch houses complete with green roofs, planted with alpines.  Gosh, they were cute.

[Hoy]

Rick, was it only one winner at each table?

Tim, exciting project! keep us informed how it develops!

[RickR]

1 centerpiece per tabie = 1 winner per table.

But for the last ten years, it has become a voluntary tradition at our banquets that anyone can bring door prizes if they want.  We usually have more gifts than there are attendees!  We've had to streamline that part of the evening (door prize giveaways) because it was taking too long to distribute them!

[GreenRoofer]

For small green roof projects you can make your own media out of 80% Expanded shale clay slate (available as a concrete weight reducer at large concrete distributors) or even lava rock, lighter color the better. You can also use Pumice if you can find it in your region. Add 20% half and half mix of aged compost and pine bark mulch and you've got it. The ESCS tends to go alkaline over time, but that's not hard to fix. That is essentially an entry level green roof media, I know of one distributor that blends his own media for all his projects.

You can use a pond liner as your waterproofing membrane, and many green roofs omit the water retention layer without ill effect, especially if you don't mind irrigating once or twice a month when it's hot. 

What a fun project that would be, I've been fantasizing about greening a shed, and putting some sort of wire on the outside, and training passion vine and cucumber vine onto it, for this cool green structure.

[cohan]

I think I got the link somewhere on this forum the other day, but don't see it at a quick glance in this thread, so just in case- do check out the green roof plant selections at hardyplants.com

[GreenRoofer]

So HardyPlants.com advocates Achillea, Allium, Aquilegia, Acaena, Sedum, and Dianthus. One of the Alliums they suggest is A. tricoccum, a woodland plant. The Aquilegias, Achilleas, and Dianthus would melt out in an extensive system. They might survive in Semi-intensive. Good source for seeds. Not sure about the Acaena, that's new to me.  I'm trialing Aquilegia caerula, and A. canadensis. I'm hoping they like growing in 6inches of gravelly medium in the hot dry sun. They'll be watered a little, but the ultimate goal is to not water more than once a month. I cheated last summer because of the drought and heat wave. I don't expect much to survive when it's 100 and hasn't rained in 3 months, including me! It's hot up there, and I can't take it for long sometimes. It's fun to garden somewhere that almost no one is allowed to go, no rabbits, no deer, no slugs. There's pigeons, crows, songbirds, lots of killdeer, tons of insects at any floor, mainly grasshoppers, spiders, syrphid flies, wasps, bees, butterflies and moths. The flying insects become very rare on the really tall buildings. Everything else can live happily on the top of skyscrapers, nature is amazing. One book people on here might like, is called 'Life at the Limits', it's about life existing where it would seem unlikely.

Lots of the plants that fail on the green roof will likely end up in my future garden or current outdoor windowsill planters. We had an icestorm in Chicago last night, all my plants had a thick coat of ice.

[RickR]

I have encountered some questionable advice in the past, too, on hardyplants.com.

 Allium tricoccum, especially, would be a terrible green roof plant! 
I think they just listed their entire selection of Alliums, without regard to speciesl 

[cohan]

In my many years living in large cities, I was very seldom on any kind of rooftop! Mind you I only very rarely lived or worked in high rises.. I did have a few seasonal pots outside a second story door on a little patch of roof in a 3 story Victorian house, but that's about it! Interesting to know what birds and bugs make it to the heights!

I wonder if you are familiar with the great (late) Brasilian modernist landscape architect Burle Marx? He's a long time favourite of mine, and I was recently looking at some of his gardens, and noted a number of roof installations (sorry, don't remember which of those shown at the link below included rooves)- usually including water.. these were long before the current interest in green rooves..
http://www.mraggett.co.uk/rbm/index.htm

[Tim Ingram]

This gets more and more interesting when you start to think of city buildings as simply being another ecosystem, and it is obvious that plants are a lot more finely tuned to environments than we often give them credit. I have a book by the incredible French plantsman, Patrick Blanc, who creates vertical plantings on buildings. What comes across is how closely he has studied natural ecosystems where plants grow on rocks and in such extreme conditions and he has developed his plantings on such individual study. It seems obvious but it takes a lot of confidence to follow your own nose and work it through. The results are amazing and completely transform the barren appearance of many city landscapes. That combination that Mark mentions between architects and plantspeople is a brilliant one when it's allowed to come off.