How to Garden on a Slope: The Best Plants and Tips to Beautify a Hilly Yard
Tracy Heuermann transformed the steep grade of her Illinois backyard into a cascading garden. Here's how she did it — and how you can use her ideas in your own not-so-flat yard.
When Tracy first visited her future home on a one-acre site north of Peoria, she saw a treacherous hillside eroded into deep ruts. Water and gravity had steadily conspired to carry away topsoil and nutrients. Railroad ties barely held the hillside in place. It all got Tracy's imagination churning — enough to buy the place. A longtime Master Gardener and co-founder of the Midwest Hosta Society, she could see the potential: flowers grown on inclines, ascending like clouds of texture and color to embellish the slope.
Tracy and her contractor husband, Victor, visited the inspiring hillside gardens of England's famed Chelsea Flower Show. "The terracing on the cliff overlook at Kiftsgate made me believe that we could do this in our backyard," Tracy says. The couple carved five levels from their yard's heavy, clay-based soil and poured 12-foot concrete retaining walls to brace the tiers. About half of the height of each wall plunges below the surface of the hillside, anchoring it to the land. To soften the look of the man-made walls and transition the garden into the surrounding woodland, Tracy incorporated free-flowing, organic design elements, such as curvy grass paths and tumbling phlox.
Today, Tracy and her husband have a beautiful hillside garden overlooking the emerald panorama of the Illinois River Valley. Tracy and Victor continue to develop the garden, nurturing new specimens and caring for established ones. "It's essential that the garden bring joy to you," Tracy says. "This one's brought a lot of joy to my family."
Here are Tracy's expert tips on how to fight soil erosion and which plants to choose for a slope.
How to Plant on a Slope
Using these savvy tactics, Tracy turned eroded land into a fertile hillside.
Bind Soil with Sturdy Roots
Any plant helps, but those with deep, clumping roots (trees, shrubs, grasses) are especially effective, as are groundcovers, which find and fill empty spaces.
Related: 15 Easy Midwest Groundcovers
Remove Weeds Carefully
Pulling them disturbs fragile soil. Healthy plantings and groundcovers will eventually crowd out most weeds. Until then, use mulch to smother weeds and to fortify the soil. Pull weeds when they're small. Knock dirt from roots and put it back in the ground.
Make a Rock Garden
Place stones or boulders among plants to trap soil and moisture and slow water runoff. You'll get a more natural look by scattering rocks of a uniform type.
Build Terraces and Retaining Walls
It's a costly solution, and you probably need a landscape contractor for help. But terraces, softened by cascading plants such as creeping phlox, dramatically transform even the toughest terrain.
Best Plants for a Slope
What are the best plants for a slope? Here are some of Tracy Heuermann's best bets plus picks from The Best Plants for 30 Tough Sites, compiled by University of Minnesota Extension Master Gardeners.
Candytuft (Iberis sempervirens)
Fragrant white flower clusters stand 12 inches tall on 'Snowflake' and 'Purity'. Zones 5-9.
Tracy's favorite, 'Rozanne', spreads rapidly and bears near-opalescent purple petals. Not to be confused with pelargonium, commonly referred to as geranium. Zone 5.
Creeping Myrtle (Vinca minor)
Tracy plants these deer-resistant purple, blue or white starlike flowers at the border of the forest preserve. Zones 4-9.
Creeping Phlox (Phlox subulata)
This lime-green, furry mat blooms wildly with pink, red, purple or white flowers in late spring and early summer. Zones 3-8.
'Flower Carpet' Rose (Rosa)
Spreading vigorously up to 4 feet, this groundcover rose pretties a slope with deep rose-pink blooms. Zones 5-8.
Siberian irises wave purple blooms in early spring; the bright green, grasslike leaves create a textural backdrop when the blooms are spent. Zones 4-9.
Mix tough shrubs and perennials among groundcovers to add taller accents on a slope. A favorite for shady gardens, hostas distinguish themselves with bold leaves in shades of green. Zones 3-8.
Mock Orange (Philadelphus) Extremely fragrant, this shrub blooms reliably, even in poor soils. Zones 5-8.
Colorful, bell-shape buds shoot off erect, spiky stems on this natural slope inhabitant. Zones 5-10.
Snowberry (Symphoricarpos var. laevigatus)
Tiny pink flowers burst out in summer, followed by namesake "snowball" berries, which last well into winter. Zones 3-7.
Nectar-filled magenta or white flowers draw hummingbirds. Tracy grows several varieties, including 'Wine and Roses' (Zone 4), 'Java Red' (Zones 4-8), 'Pink Princess' (Zones 5-9) and 'Polka' (Zones 4-7).