W
hat can I grow on a steep slope that is difficult to mow?” This is a question I frequently get asked by homeowners. And for good reason—working on slopes is uncomfortable, dangerous, and requires extra effort. An alternative to maintaining and mowing turf on these areas is to establish aggressive plants that are allowed to seed and sucker freely to fill gaps quickly, keep weeds out, and potentially cover large areas. When plants are allowed to meander, they look natural, like a tossed salad, so it’s a good idea to surround these areas with a split-rail fence or mowed turf walkway (if possible) to make them look as intentional as you can. It’s also best to include various species that bloom in spring, summer, and fall that also have attractive seed heads in winter. Densely planted, naturalisticstyle gardens don’t require mulching after being fully established (this is called green or living mulch), unlike conventional gardens where wood or leaf mulch is repeatedly applied. Mulch may wash away in heavy storms, so green mulch gardens work well on slopes. That said, mulching newly planted perennials and grasses is recommended during establishment (usually two growing seasons). The plants recommended below are long-lived and densely leafed to shade out weeds. When slopes are greater than six-to-one (about 15% slope), a biodegradable erosion blanket is recommended. These are made of biodegradable plastic mesh, woven with natural fibers like straw, wood shavings or shredded coconut hull. When planting into erosion blankets, the smaller the plant, the easier it is to install. Deep plugs work best for this application and will save you time and money. Plant them close,
Photos by Scott Woodbury.
Plant Aggressive Native Plants on Steep Slopes: An Alternative to Mowing Grass
Prairie dropseed (above) and little bluestem (below) easily adapt to slopes.
Blue wild indigo, golden alexander, and shining bluestar work well together. about 15 inches apart, and use an online plant calculator to determine the quantity (like the one at classygroundcovers.com). There are many native plants that work well on full sun slopes. Solid-performing perennials include (in order of bloom) golden Alexander (Zizia aurea), blue wild indigo (Baptisia australis), shining blue
SCOTT WOODBURY Horticulturist 10
July 2021 | kcgmag.com
star (Amsonia illustris), wild strawberry (Fragaria virginiana), Ohio spiderwort (Tradescantia ohiensis), Texas green eyes (Berlandiera texana), common milkweed (Asclepias syriaca), gray-headed prairie coneflower (Ratibida pinnata), wild bergamot (Monarda fistulosa), obedient plant (Physostegia virginiana), sweet coneflower (Rudbeckia subto-
mentosa), willow-leaved sunflower (Helianthus salicifolius), stiff goldenrod (Solidago rigida) and aromatic aster (Aster oblongifolius). These are medium to tall plants (3 to 5 ft.). The best companion grasses and sedges in this height range include little bluestem (Schizachyrium scoparium), switch grass, (Panicum virgatum), prairie sedge (Carex bicknellii), Short’s sedge (Carex shortiana), Bush’s sedge (Carex bushii), and yellow-fruited fox sedge (Carex annectans). In part shade, the best perennials to colonize on a slope (in order of bloom) include Jacob’s ladder (Polemonium reptans), common violet (Viola sororia, which may already exist on your property), wild geranium (Geranium maculatum), purple coneflower (Echinacea purpurea), star coreopsis (Coreopsis pubescens), purple Joe-pye (Eupatorium purpurea), woodland knotweed (Polygonum virginianum), garden phlox (Phlox paniculata), rose turtlehead (Chelone obliqua), and showy goldenrod (Solidago speciosa). The best grasses and sedges to include are river oats (Chasmanthium latifolium), American beakgrain (Diarrhena obovata), palm sedge (Carex muskingumensis), bur sedge (Carex grayii) and brown fox sedge (Carex vulpinoidea). Steeply sloped areas are infrequently used, frequently neglected, and often out of sight in the side or back yard. Instead of mowing or planting a conventional garden on it, why not consider a natural alternative. It’s a perfect place and time to tinker with a natural style of gardening. Remember to start small, build on your successes, cut plants back in March, cut spent stems high for the bees (10-12 inches) and make stem clippings that are small that fall to the ground with no need to rake up. This should make for happier gardening!
Horticulturist Scott Woodbury is the Curator of the Whitmore Wildflower Garden at Shaw Nature Reserve in Gray Summit, MO, where he has worked with native plant propagation, design, and education for 30 years. He also is an advisor to the Missouri Prairie Foundation’s Grow Native! program. Find native plants and seeds suppliers at grownative.org.
