CATS ON A COOL, GREEN ROOF
Not Green Enough
I’m looking up at my green roof, my evergreen roof, and it’s not green enough. Literally. I had expected that by now the roof would be solid green. It’s not.
The green of this roof was supposed to come from the plants growing on it. Because conditions up on the roof are very harsh, the plants I chose were tough ones, hens-and-chicks (Sempervivum spp.). Hens-and-chicks look like little cabbage heads of stubby, succulent leaves. Baby plants push out from around the mother plants, grow, and make more babies, and so on, ad infinitum. Or so I hoped.
The roof only has a couple of inches of “soil” on it and covers a porch, so has no heated space or insulation beneath it. If winter temperatures plummet to 10 degrees below zero, not uncommon here, temperatures within that thin layer of soil also plummet to 10 degrees below zero. If summer temperatures hit 95° in the shade, the soil, which is shaded at one end, also hits 95° — and more in the sunny end. The roof never gets watered, except by natural rainfall.
The hens-and-chicks have established and survived and spread. But not enough. By now, I expected the roof be packed solid with hens-and-chicks, with excess plants spilling decoratively over the front edge. But too much soil still shows. Part of the green problem is that hens-and-chicks are not all that green; the leaves are more pale blue-gray.
Enter Angelina
So I’ve been taking steps to green up the roof.
The first step has been introducing a companion plant for the hens-and-chicks. The plant, which I believe is ‘Angelina’ rocky stonecrop (Sedum rupestre), has been magically appearing here and there in and around my rock walls. Well, not magically. As with other succulents, ‘Angelina’ easily grows into whole new plants wherever any piece of stem or leaf merely drops onto the soil. Over the past few years, whenever I’m so inclined, I grab a few pieces of ‘Angelina’ and toss them up on the roof. They’ve rooted and spread, parading up there as forest-green patches.
I periodically get more serious with ‘Angelina’. “More serious” means filling some cell-type seedling flats with a “soil” of equal parts moist peat and perlite, and poking inch-long pieces of leafy ‘Angelina’ stems into the mix. After a winter in the greenhouse or a sunny window, those cuttings are rooted enough to plug into holes I dibble into the soil on the roof among the hens-and-chicks. The roof is a little more than 100 square feet. Each plant could potentially fill up a square foot in a couple of seasons, so 100 cuttings of this plant would do the trick and take up only a couple of square feet of space in their holding cells.
Another step to making the rooftop greener is to beef up the “soil.” The soil is actually a mix of equal parts peat and calcined montmorillonite clay (a.k.a. kitty litter, unused). The mix is heavy enough not to blow away, and the peat is relatively resistant to decomposition. Some shovelfuls of this mix periodically tossed up on the roof replace what’s washed away or settled.
The mix is lean in nutrients so, come spring, I could also beef up the rooftop with some fertilizer. Not much, though, because succulents are light feeders and too much fertility would encourage weeds.
Is Green Better Than . . . ?
I don’t get it. Green roofs are so “in” these days, for their green appearance and for their environmental green-ness. Sure, green roofs insulate rooms below from heat and cold. And green roofs capture and evaporate some rainwater rather than let it run down gutter pipes and into sewers or streams. The air above green roofs stays cooler than that above conventional roofs, so heat islands aren’t created.
But are the above good enough reasons to put plants on a roof? After all, good insulation also insulates, a lot better than soil and with a lot less weight. And how much water could a roof of succulent plants — plants known for their low water usage — evaporate?
Much as I love plants, I’d rather see solar panels on roofs. My green roof is for looks (and not sunny enough for solar panels).
And A Bow To The Weeds
My green roof is a testimonial to the tenacity of plants. Despite the leanness of the soil mix and its being initially pretty much weed-free, some weeds have colonized the roof. And they survive, despite the harsh growing conditions up there.
The weeds that came in weren’t succulents, but grasses and perennials such as foxtail grass and goldenrod. Every time I look up at the roof, I am awed at how these and other plants not only got there, but how they manage to survive there year after year.
Weeding up there would seem such a travesty — and be very difficult.
UPCOMING PRESENTATIONS
I will be offering lectures and workshops at a number of venues across the country in the upcoming year. If interested, go to the “Lecture” page of this website for a current listing, which will be updated as needed.
IN WITH ENDIVE, OUT WITH ASPARAGUS
First Harvest At Season’s End
Finally, I’m harvesting endive from the garden, just as planned when I settled seeds into mini-furrows in a seed flat back in July. After leaves unfolded on the seedlings, I gently lifted them up and out of their seed flat, helping them up with a spatula slid beneath their roots, and into individual cells in a GrowEase Seed Starter.
Also as planned, a bed in the vegetable garden was freed up from harvested sweet corn in early September. After removing corn stalks and slathering an inch of compost on top of the bed, the endive plants were snuggled in, 2 rows down the 3-foot-wide bed, with one foot between the plants in each row. In October, I laid row cover over the plants, plus a tunnel of clear plastic film supported by hoops, to protect plants from bitterest cold.
Endive harvest could have begun earlier. But there was no need to, with so much other fresh salad fixings in the garden. And cold weather anyway helps bring out the best in endive. The inner leaves, partially blanched as they folded in among themselves from close planting, are now especially sweet, succulent, tender, and tasty.
What Endive, Who?
Just to be clear on the identity of my endive, it’s botanically Cichorium endivia var. latifolia, also called escarole, broad-leaved endive, or Batavian endive. Besides delicious fresh, it’s a key ingredient in the classic Italian white bean and endive soup.
I used to also grow another endive, C. endivia var. crispum, also called curly endive or frisée. It’s very similar, except for frilly leaves. In my experience, it’s less succulent and more easily damaged by cold.
We’re not yet finished with “endives.” There’s also Cichorium intybus, also known as Belgian endive or witloof chicory, with small heads that are torpedo-shaped and pale green or white.
More machinations are needed to grow this Belgian endive, beginning with sowing in spring and waiting the whole season for a large taproot to develp. At season’s end, the roots are dug up, trimmed to a foot or so long, then packed together upright in boxes of loose potting soil, sawdust, or anything else that will hold moisture. The roots resprout, and the goal is to keep the developing heads in the dark, either by putting a few inch depth of sawdust or sand over the roots or by keeping the whole box in darkness. Too much trouble for me. Plus, very little flavor. (Also, mine weren’t all that successful.)
Bye, Bye Asparagus
Speaking of pale leaves, I’m happy that my asparagus’ leaves yellowed a couple of weeks ago. The plants had been growing vigorously all season since harvest ended in July, the green stems and leaves gathering sunlight to pump energy down to the roots, to store and then fuel next year’s growth of the young spears. Finally, the plants yellowed as what nutrients were still left in the stems and leaves headed downward, to the roots.
My short-bladed brush scythe was the perfect tool to make quick work of the plants, a fluffy addition to the compost pile.
After July, germinating and growing weeds became too hard to reach and root out among the 6-foot-high forest of feathery stalks. With the asparagus shoots and leaves cleared away, I was recently able get into that bed for a final weeding. The two-inch-deep mulch of leaf mold I spread after weeding will slow weeds down next year, conserve soil moisture, and feed soil microbes and, in turn, the asparagus plants for what I predict will be a bountiful harvest.
