Pennsylvania sedge (Carex pensylvanica): the ultimate lawn grass for shade? Photo: mgnv.org
Are you looking for a low-growing grass for a shady spot, one that could even be a lawn substitute? What about Pennsylvania sedge (Carex pensylvanica)?
Now, to be honest, it’s not really a grass (Poaceae), but a sedge (Cyperaceae), but it sure looks like one, with long, narrow, fine-textured green leaves that arch out around the mother plant. It grows to be about 8 to 10 inches (20 to 25 cm) in height if unmowed and is semi-evergreen, that is, it will remain evergreen in mild climates, but die back in cold ones, regrowing new leaves from the base in the spring. Curiously, in my very cold climate (USDA zone 3), it has proven faithfully evergreen, probably because it’s covered in snow from November to April and snow is an excellent insulator. Where it does die back, however, it recovers rapidly, sprouting very early in the spring. In fact, one common name is “early sedge!”
It also blooms early in the year, but the brownish flower spikes are soon hidden by the growing leaves and aren’t that noticeable.
I’m quite amazed by its adaptability. It’s said to be a shade grass, yet it does fine in full sun as well (although only if the soil remains somewhat moist at all times). Mine is positively thriving in dry shade under conifers where little else will grow, although it’s very, very slow to spread under such conditions. In more humid soils, it will produce more numerous offsets on longer rhizomes and fill in better.
I keep reading it needs “good soil,” but I find it seems rather indifferent to soil type except maybe not liking very alkaline ones. Certainly, it really doesn’t seem to need fertilizer.
Can you mow it? Sure, perhaps twice or three times a season (much less than regular lawn grass). Probably early in the year and again in fall (it doesn’t grow much in the heat of summer). Or just let it grow, in which case it takes on a sort of swirly appearance.
In the wild (it’s native to much of eastern North America, from Quebec to Manitoba in the North and Georgia to Missouri in the south), it tends to form large monotypic patches (yes, a natural monoculture!). You don’t have to force it to be a lawn, it wants to be a lawn!
Pennsylvania sedge is only moderately tolerant of foot traffic: you certainly wouldn’t want to walk on it daily or use it for a playing field.
It’s considered resistant to deer and rabbits and has no major disease or insect problems. It’s a host plant for several North American butterflies, but the caterpillars seem to do little visible damage.
As for hardiness, it grows in USDA hardiness zones 3 to 8. I suspect it is even hardier than that: time will tell!
Ideally, you’d want a shade lawn you can grow from seed: that would be a cheap and fast way of getting results. Well, Pennsylvania sedge won’t do that. It’s slow to grow from seed and germination tends to be poor. You’d likely be wasting your time growing it that way.
So, what you’re going to want are plugs you could space about 6 inches (15 cm) apart in deep shade or dry conditions, 12 inches (30 cm) apart in sun or partial shade and moister conditions.
Good luck with that, though! Locally, I can only find Pennsylvania sedge in a few specialist ornamental grass nurseries in 6-inch pots: way too expensive for a lawn project. So, I’ve taken to dividing my original plant each spring to cover a larger and larger area. It’s slow-going, but getting faster as the divisions produce divisions and they too produce divisions. I’ll be there soon!
Hey garden centers! Can you wake up and start selling your clients plugs of this plant at reasonable prices? After all, there’s a huge demand for shade lawns and this is about the only “grass” that will fill the bill. If I were looking for a lawn for a dark corner and you offered trays of plugs ready to plant at a reasonable price, I’d be on it like a duck on slugs and I’m sure other gardeners would as well.