Ed Snodgrass, owner of Emory Knoll Farms and Green Roof Plants will be speaking for our NARGS Chapter this Saturday. I am going to a dinner for him tonight too. If anyone has some specific questions for him, I should be able to ask him. I haven't read his book(s) yet, but it (and him) should be interesting. It's surprising how many rock garden plants do well on the roof.
Roof Gardens
See if you can find out how much the "extensive" (shallow) type of plantings actually weigh, soaking wet, say after a heavy rain. I (and the architect...) figure if it weighs less than fifteen pounds per square foot, we will try it this year on a house we are currently working on. Also, is an epoxy roof a suitable candidate or should an "epdm" roofing system be used?
Thanks, Leftwood. That Green Roof Plants site is great, I hadn't run accross it yet in researching a planted roof. Guess I better buy the book!
http://www.greenroofplants.com/
Good questions, Claypa. Somethings I'd like to know too.
Back from dinner and as usual, our speaker is a dynamic man. Conversation led to many subjects. He is a wealth of knowledge, and is experienced in alternative energy sources too. He waters his entire nursery with a very small pump, smaller than our house sump pumps, and it runs on solar energy.
Back from the banquet. Great talk, great banquet. 68 people attended, more than when Panayoti was here. (But we've been working hard on new recruits.) As is now our tradition, some (hopefully most) of us bring appropriate anonymous gifts to be redistributed among the attendees. I also brought Giant pussywillows (Salix chaenomeloides) from my yard that seemed to be perfectly timed to coincide with the gathering. The bouquet was 4.5ft x 4ft, and everyone was glad when I said I didn't want any to take back. (People love anything free.)
Contrary to what you might think from Ed's site regarding what he sells at his nursery, Ed Snodgrass does a lot of green roofs without sedums too. In his presentation, he spoke more in general terms regarding specifics, but was happy (and able) to answer specific questions we had.
Regular soils are NOT used on roofs. Free draining mediums based from things like pumice or other volcanic rock, baked clay aggregate, etc. are used. Things used as light weight additives in commercial concrete are good, he says, because they can withstand the huge temperature fluctuations without breaking down. A baked clay aggregate called Turface is readily available in Minnesota. One of our Chapter members has had a self-made green roof for more than 10 years, another for 20 years, and both used Turface as their soil medium base. Ed says you could use pea gravel with some compost if you wanted, but that would be a very heavy roof!
So, using the recommended soil mediums, figure a maximum of 6-7 pounds per square foot vertical inch. Thus, for a 3 inch cover, that would be 18-21 pounds per square foot. This is a laboratory testing at full water saturation. Ed stressed that this is in addition to other load requirements, like snow.
When I asked him about the waterproof layer, he said inorganic products would be best as plants cannot "eat away" at them. Things like epdm, pvc, etc. are good, as opposed to something like asphalt. He cautioned me when I use the word "waterproof", and said that many times the glue used for epdm is water soluble. I mentioned epoxy, and Ed didn't know anything about it. There was another greenroof contractor in the audience, and he hadn't heard of its use either.
He also made it clear that green roofs are probably not maintenance free from a gardening standpoint, especially if they are given additional water. A grade of 3 inches per foot is the maximum you can get away with without using some kind of baffle system to keep the medium from sliding off the roof.
Thank you for sharing the information Rick.
Can I take you off topic for a bit to ask what your chapter
did to grow the membership?
Tammy, we have been participating in as many garden fairs as possible. You know, where you have a table, perhaps with some rock garden books, display troughs, even empty troughs(styrofoam ones are all the rage now), membership info (don't forget the national too), yearly meeting schedule, sample newsletters, etc. We have them at our Arboretum, a couple nurseries sponsor them at their nurseries, and some cities/suburbs in the area have them too. A state fair display when we can.
We put together a slide presentation on rock gardens, with a written narration (to make it easy), to give to other groups like local garden clubs. Anyone in our Chapter is encouraged to sign it out and use it.
We have a publicity chair who keeps a list of contacts, like for the Arboretum newsletter, Minnesota State Horticultural Society, local and city newspapers, etc. She keeps them abreast of our upcoming activities so they can print them in their appropriate printed sections. Articles on rock gardening in said periodicals helps too.
Basically, it's get the word out any way you can. Members becoming involved in other Societies/garden clubs are natural focal points for questions by interested parties. I have recruited two members from the GardenWeb community.
I have to say also, that since we made our spring plant sale open to the public (and publicized it), we have been raising a lot more money to bring in better speakers at our regular meetings in addition to our annual banquet. This sale is probably about one-fourth alpine plants. We have a membership table there too, and keep a list from customers that want to be contacted about future events.
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If you'd like to read a bit more about my recent banquet experience (admittedly a bit egocentric) see this thread and scroll down to Leftwood's March 30 entry.
http://davesgarden.com/community/forums/t/827365/#new
Yet another thread to watch.
Well, I guess it's up to the architect to decide if our roof can be made stronger. Around here roofs have to be built to hold 36" (if I remember right) of snow, because it can and does happen once in a great while. The fifteen pounds I mentioned was our leeway beyond the expected loads. Turface weighs 9.5 pounds a square foot at 3 inches deep, and it's easy to believe it could hold a gallon of water (another 8 pounds or so), plus the plants... I like sedums but it's nice to know there are other choices. I'll contact that nursery and see if they can help. Maybe some plants would be lighter than others - it sounds funny, but it might make this possible.