WHAT CAN I PLANT ON MY SLOPE?

By Lynn Kuhn | Special to Lake Panorama Times

As I reflect on the 2024 season, one of the most common requests from clients and friends has been, “What can I plant on my slope?” This topic certainly deserves more time and space than I can give it here, so I’ve distilled my list down to just three shrubs and three grasses. My criteria is tough. To make the list, the plants MUST have the following characteristics:

Deep and/or spreading root system, preferably fibrous
Shorter than 4’
Seasonal interest with blooms, fall color or both
Clean, good-looking foliage
Tolerant of deer, drought and full sun
Low maintenance once established

THREE SHRUBS FOR SLOPES

1. ARONIA (Chokeberry)

You may have heard about Aronia, the superfood chock-full of flavor, antioxidants and more. And, yes, you can make wine from it. But it is also a super-shrub known for its gorgeous glossy leaves, white flowers and intense red-orange fall foliage. Recently introduced cultivars are all of the above plus compact in habit. Look for these cultivars:

Ground Hug
8-12” tall by 2-3’ spread
Low Scape Hedger
3’ tall by 3’ spread
Low Scape Mound
18-24” tall by 18-24” spread
Iroquois Beauty
2-3’ tall by 3-4’ spread

2. DIERVILLA (Bush-honeysuckle)

Despite its common name, Diervilla is not related to the invasive non-native honeysuckle shrub called Lonicera. To learn more about Lonicera and its long list of problems, go to Identify and Manage Invasive Bush Honeysuckle | Good Growing | Illinois Extension | UIUC.

Diervilla not only meets the criteria listed above but also offers an opportunity to combine different cultivars for a showy matrix of colored foliage. This is also due to the way it colonizes, growing into a beautiful thicket that hugs the slope. The key is to select cultivars that are relatively the same size. The cultivars listed below will grow to 3-4’ tall by 3-4’ spread.

Kodiak Black
Kodiak Red
Kodiak Orange
Kodiak Fresh
Nightglow
Butterfly

3. GROW-LOW SUMAC (Rhus aromatica “Grow-Low”)

The sumac family is filled with uniquely beautiful plants, especially the colonies of Smooth Sumac along Iowa roadsides that are turning bright red this time of year. Grow-Low Sumac’s form and texture is remarkably different. Like other members of the family, it is extremely hardy and tolerant of just about everything you can think of including deer, rabbits, black walnuts, clay soil, salt and drought. Mature size is 2-3’ tall by 6-8’ spread. Fall color varies depending on how much sun/shade. Expect yellow fall color in shade and bright orange to red in full sun. When planting on a slope, I recommend spacing them 5’ on center to cover the slope quickly. This plant doesn’t mind a little bit of overlapping.

THREE NATIVE GRASSES FOR SLOPES

An unfortunate common sight on slopes is a combination of many different shallow rooted ornamental plants planted too far apart with mulch sliding down the slope between groupings. This is a high maintenance situation that does not prevent erosion. Instead, plant a deep-rooted native grass, such as one from this list. The deep fibrous root system will act as a filter for dirty runoff and pollutants from surrounding streets and rooftops. At the same time, water percolates into the soil which keeps the plants happy and helps to recharge groundwater aquifers. Once the grass is established, add small pockets of colorful perennials or bulbs.

1. PRAIRIE DROPSEED (Sporobolis heterolepis)

Prairie dropseed matures in about three years and is well worth the wait. Consider a companion planting of Carex brevior (aka Plains Oval Sedge) amongst Prairie Dropseed to provide early spring coverage. Another lovely companion is Kalimeris incisa “Blue Star,” which blooms late and resembles a small daisy or aster.

Prairie dropseed will grow 6-9” tall in early spring, then to 30-40” tall late summer in bloom. Expect a spread of 12-18” after two years, and 24-30” after four to five years. There are a few nice cultivars, however, for slope coverage, I recommend the straight species.

2. LITTLE BLUESTEM (Schizachyrium scoparium)

There are many cultivars, or nativars, of Little Bluestem. I chose the following due to their shorter height and other characteristics. All will have 3-5’ deep root systems depending on the overall diversity of the surrounding plantings.

Blaze (best fall color)
2-3’ tall by 18-24” spread
Carousel
2-3’ tall by 2-3’ spread
Standing Ovation (upright and won’t flop with burgundy tips)
3-4’ tall by 12-18” spread
Prairie Blues
3-4’ tall by 18-24” spread
Twilight Zone
3-4’ tall by 18-24” spread

3. SIDE OATS GRAMA (Bouteloua gracilis)

Side oats grama’s roots will extend 2-4’ into just about any soil. One of its most unique characteristics is the row of flowers along the stalks that will form into seeds. It also can be used as a lawn substitute. The most beautiful cultivar is “Blonde Ambition” at a mature size of 2-3’ tall by 2-3’ wide.

MAINTENANCE TIPS

Herbaceous plants (grasses, perennials, bulbs) can be cut back early spring with a mulching mower, with no need to remove the cuttings.

Keep weeds under control and water regularly the first two years. Once established and filled in, weeds will be minimal and supplemental water should be unnecessary.

For woody plants, I recommend coppicing, which is an underused practice of cutting woodies back to the ground in early spring usually every three to 10 years, depending on the condition of the plant and its ability to recover. Coppicing can keep the foliage looking fresh and more vivid.

Keep volunteer woody plants from getting established. Oak and mulberry trees are notorious for this. Pull them if you can or cut them back and treat the stump to ensure it won’t grow right back. If you stay ahead of it, it will diminish over time.

Have you had success on your lakeside slope? I would love to hear about it. Email me your success stories and questions at lynn@conversationgardens.com.