8 minute read
There's a Sedge for That
Image: Spring flowers of Hayden’s sedge or cloud sedge (Carex haydenii) glow a golden wheat color against their green foliage.
Grass-like sedges are ecologically beneficial and come in infinite varieties.
STORY MICHELLE BRUHN
PHOTOS MT. CUBA CENTER
Sedges can easily get swept into the “just like grass” group. But, if we slow down and maybe even bend down to get a closer look, the diversity and ecological benefits of sedges may sweep you right off your feet.
I became obsessed with these plants as a young girl after noticing the little yellow pom pom blooms coming from what looked like grass. I was instantly intrigued. A few varieties of sedge happen to grow wild in the oak and maple hardwood forests and bogs that I grew up with. I now know that it was a sedge, specifically Carex pensylvanica, that caught my eye way back when. I still admire how Pennsylvania sedge produces their little tufts of green on the dry hills under the oaks. Their bloom time reminds me to hunt for the nearby patches of wild ramps.
Because sedges can be found across North America, you’ve likely seen them on a hike if not in a cultivated garden. Carex is a genus of herbaceous grass-like perennials with solid, three-sided/triangular stems.
There are many variations of the following rhyme, but this gives us the general idea:
Sedges have edges, rushes are round, grasses have knees that bend to the ground.
Most of the time this handy mnemonic device rings true, but nature likes to keep us guessing. With well over a thousand species worldwide, several hundred species in the United States and close to 200 species in Minnesota, diversity abounds. You can catch some of that sedge diversity on display with the 30-plus varieties grown at the Minnesota Landscape Arboretum in Chaska, Minn.
ABUNDANT DIVERSITY
Naming exactly which sedge you’re looking at can be extremely tricky. Sedges tend to require close inspection of the seeds—while some require microscopic viewing of the floral parts—to pinpoint the exact variety. But for the average home gardener, more important (and more useful) than knowing the exact Latin name is knowing how they fit into the landscape.
Because they grow in a shockingly wide array of habitats, there is “a Carex for every garden” says Sam Hoadley, Trial Garden Manager at Mt. Cuba Center in Delaware. Sam and his team recently completed a four-year trial evaluating 70 types of Carex. The results are in, showing sedges to be one of the most versatile problem-solving plants for home gardens. “Carex woodii, or Wood’s sedge, was the top performer in the trial, demonstrating the genus’ ornamental value and versatility in the garden. It excels in both sun and shade and offers a carpet of straw-colored flowers from April to May,” Sam says.
Sedges are also extremely low-maintenance plants. “We did almost nothing besides watering the plants in the first year,” Sam adds. “We found there’s literally a Carex for every garden application, from rocky outcrops to wet, shady bogs. And because they can thrive in such diverse growing conditions, they can be used as a unifying feature in a landscape to bring your eye from shade to sun and back again.”
ECOSYSTEM ALL-STAR
Carex also provide food and shelter for a wide array of native wildlife. Because almost all sedges are wind pollinated, the interactions might look different than what we’re used to (another way this plant family can get overlooked) but are just as important to the biodiversity of an area.
“Sedges provide food for specific native larvae like our Minnesota native Skipper butterflies (Lepidoptera hesperiidae),” says professor emeritus and University of Minnesota Extension specialist Mary Hockenberry Meyer. While insect larvae feed on the leaves, sedge seeds are enjoyed by birds and other insects.
In the Mt. Cuba Center Trial Gardens, Sam and his crew saw abundant frogs, toads and spiders in the Carex trial gardens, likely because the plants kept the surface of soil moist and provided ideal habitat.
With the increase in ecologically focused gardening, native sedges have become more sought -after for waterlogged applications (hello rain gardens) and as lawn alternatives. However, there are many other worthy ways to use this plant’s natural tendencies.
“Sedges are a group of perennials that can create a dense cover that reduces erosion and weed competition,” says Mary Hockenberry Meyer. “They have a place in the ‘matrix’ ecological system of landscaping, where uniformity is valued and tends to create a base level of growth covering the ground completely.”
Most grasses spread by bunching roots, while some sedges spread via rhizomes. This, coupled with Carex’s tendency toward deep and thick roots makes it great at preventing soil erosion and suppressing other weeds.
HOW TO USE SEDGES IN YOUR SPACE
Ornamental use
For ornamental use, Sam suggests Carex cherokeensis (Cherokee sedge) for its dark green foliage and many of the palm sedges for their unique form and flowers.
Native lawn alternative
A few Carex varieties tolerate annual mowing and are drought tolerant, making them smart options for lawn alternatives. They don’t do well with heavy foot traffic, though, so Mary says they’re best treated as ground cover that can more easily be kept in check. One of the biggest surprises for Sam’s team was that even when mowed every two weeks at 4 inches, Carex woodii made a decent lawn replacement option, especially for dry shade.”
• Carex pensylvanica: Pennsylvania sedge
• Carex woodii: Wood’s Sedge
• Carex flacca: blue sedge (on the aggressive side)
Average to Wet Shade
These varieties show off wider, ½ inch to ¾-inch-wide leaves that need at least partial shade to thrive. These can rival hostas for their variegated leaves. While tending to be slower growing, they will mature into 6- to 15-inch mounds of dense foliage.
• Carex laxiculmis: weak-stemmed wood sedge
• Carex morrowii: Japanese sedge (not native)
Dry shade
“Carex generally tolerate competition with tree roots like maples and spruce and offer a native alternative for planting in dry shade,” Mary says. Most sedges do well in shade in general, but for dry shade there are a few standout options.
• Carex pensylvanica: Pennsylvania sedge
• Carex radiata: Eastern star sedge
• Carex rosea: Rosy/curly wood sedge
Rain garden and wetland restoration
Aided by the shape of the stems, sedges can grow in low oxygen conditions by developing air channels in their leaves, stems and roots. These channels are called aerenchyma and allow oxygen to transfer from leaves to roots, making sedges at home in wetlands, bogs and rain gardens.
• Carex muskingumensis: palm sedge
• Carex bromoides: broom sedge
• Carex grayi: Gray’s sedge, or mace sedge
• Carex lupulina: hop sedge
• Carex stricta: tussock sedge
• Carex lacustris: lake sedge / hairy sedge
• Carex gynandra: Nodding sedge
SOURCING SEDGES
When sedge shopping, support trusted native plant retailers, such as Prairie Moon Nursery (prairiemoon.com) and Izel Native Plants (izelplants.com).
HOLDING SPACE
Despite their adaptability to so many diverse landscapes, they’re a little tricky to cultivate in a controlled setting. Add that they can also be difficult to distinguish, and you’ll understand why nurseries have been slow to gather enough stock. Luckily, as demand rises, so does supply.
Sedges are delightfully ubiquitous in our northern landscape, holding space everywhere from woodlands to wetlands. And, once you start noticing them in their natural habitats, you’ll want to add them to yours.
As Sam says, “Sedges add a layer of complexity and depth in any garden design, in a way that you may take for granted but you’ll miss once they’re gone.”
DID YOU KNOW?
While most sedges are wind pollinated, Carex fraseriana (Fraser’s sedge), formerly Cymophyllus fraseri, lures insect pollinators with its fragrant white flowers. Although not included in the trial, this fascinating species can be seen in the naturalistic gardens at Mt. Cuba Center.
