One of the biggies on our list of things to finish Underhill House this spring was seeding the roof. We got about 20 tons of screened, topsoil up there and planted see my post Planting Our Roof – A Prairie in the Sky https://digginginthedriftless.com/2013/05/21/planting-our-roof-a-prairie-in-the-sky/ about a month ago in mid-May.
That was intense, with the soil being hauled up in giant bucketful’s by crane, and then evened carefully out to be at least 3 inches deep everywhere on the undulating surface of our roof.
We seeded in two kinds of prairie grass that we were assured could make a go of it on a roof by the knowledgeable and helpful Prairie Nursery .
My experience is that prairie plants can be wonderfully tough – once they are established. But getting them to germinate and beat out the weed seeds in any soil they are inserted into can be tricky. Usually you nuke any bit of ground you want to turn back to prairie before planting the prairie seeds using an herbicide like Roundup.
We didn’t have that opportunity on the roof. The seed had to go into the soil and be covered with erosion mat the same day the soil was hoisted up otherwise it could all be blown away in the next big wind followed by a few dry days.
The two grasses planted are Sideoats Gramma Grass and June Grass.
Sideoats Grama Grass, Bouteloua curtipendula, is a good choice because it is one of the shorter prairie grasses and has a fibrous root rather than the downward torpedo root of so many prairie grasses. It’s drought tolerant. If it gets too dry, it will go dormant and perk up again when rain comes. It’s a warm season grass, which means it grows during the warm months of the summer. It’s also quite lovely. We’ve introduced it into our restored prairie. It can be shaded out by taller grasses, but that won’t be an issue on our roof.
Junegrass, Koeleria macrantha, another short fibrous rooted grass makes a good roof partner for Sideoats grama. It produces lustrous silver-green seed heads in early summer and grows actively when soil temps are cooler in spring and fall.
The sideoats gramma grass seeds were quite big, while the June grass seeds were extremely tiny, so I assume that the first grass up was sideoats grama. Over a week later, tiny, delicate spears of grass began coming up among their larger, earlier sisters.
Now both seem to be well established.
As to weeds, we have a few of those too, so about every week, we take a bare-foot stroll about the roof and pull out the broad-leafed interlopers.
It’s starting to look like a living roof, and that is so exciting.
There are some spots were germination has been light. Two big patches are the obvious spots where the soil was compacted by a tarp covered with a load of clay, which was carried to the roof by mistake. But there are some other thin spots too. And of course, nothing will be growing under the stones we placed along the edges to make sure the erosion mat didn’t take to the sky like a giant fibrous kite during some of the big winds we had right after planting.
Categories: Eco architecture