One of the most challenging landscape issues is what to plant and how to manage gardening on slopes and inclines.
From firsthand experience, I can confirm the ups and downs of dealing with plants on a slope. We’ve lived on one for more than 20 years, and it’s working well for us.
When slope plantings are well executed, it’s not only pretty to look at for you and passersby, but it also can be mostly trouble-free, which is the goal.
The reality with slopes is that everything goes in one direction — downward, especially soil and water. Wasting water that rolls downhill is not good in any circumstance. And forget trying to mow grass on a steep slope: You might as well install padding and safety netting at the bottom because someone along the way (probably you) will be rolling down to the bottom.
If you have several feet in length and a deep rise or an entire hillside, then landscaping the area can be a big job and probably needs to be budgeted for and planned. If your slope vision includes using rocks, stonework, boulders, terracing, or installing retaining walls, it makes sense to partner with a reputable landscape company which has completed successful slope projects. Ask for references and call them, then drive by finished projects so you can see for yourself the quality of their work.
There always seems to be a hitch or two in landscape projects. Ordinary delays just happen, from late-arriving supplies to weather postponements. Expect to possibly pay overages in time and materials if using a professional. Get permission from your local municipality if the project is on or near the public right of way. You most likely will have to submit a landscape plan and obtain a permit. Changing water flow on a slope may affect nearby yards. And always call 811 before work begins so any buried utilities are located with flags or paint.
Your plant selection should be based on the size of the area to be planted, the sun exposure, soil conditions and moisture availability. The plan should include appropriate irrigation for the plants. Consider installing drip irrigation set perpendicular to the slope, so water goes directly to each plant, making it a very efficient system with no runoff.
If the slope is currently turf grass, one workaround is to kill it and leave it in place to serve as a stabilizer and mulch for new replacement plants. Simply cut out dead turf areas where plants will be installed. In time, the new plants will grow and cover visible dead turf.
Direct seeding is tricky on slopes and can be less successful, keeping the seeds from spilling away when watered. If seeding, try using weed-free straw mulch with netting or specialized seed starter mats.
There are plenty of plants that will happily grow on slopes. Do your homework and learn about the plant characteristics:: foliage and bloom color, insect and critter resistance, wind exposure, blooming period, height and plant spread. Choose plants that have similar soil, sun and water requirements and will work for your elevation.
Plantings with a mixture of groundcovers, shrubs, native grasses and herbaceous perennials are a good strategy for slope stabilization.
Try not to place single plants here and there unless you’re going for a patchwork look. Install them in groups or drifts. Spread grasses and larger shrubs in the middle layer for continuity.
When choosing herbaceous perennials for slopes that need cutting back in spring or regular deadheading, be sure to locate them within easy reach.
Independent local nurseries often carry plants designated to grow on slopes. And don’t forget the bigger ticket options to install terracing, retaining walls of concrete, stone and brick, or add rocks and boulders. Plants can still be tucked in here and there.
Below is a short list of plants to consider that can grow well in many slope situations. They are designated by sun exposure: S: 6 or more direct hours of sun; PS: light (3-5 hours of sun), partial (sun and shade during the day); SH: mostly shady conditions.
Woody groundcovers and low shrubs
Baby Blue Rabbit brush (Chrysothamnus Ericameria nauseosus var. nauseosus): S to part SH
Bearberry, Kinnikinnick (Arctostaphylos uva-ursi): S to SH
Cotoneaster (Cotoneaster spp.): SH to part S
Creeping Oregon Grape Holly (Mahonia repens): SH to PS
English Ivy (Hedera helix): SH
Euonymus Coloratus Purple Wintercreeper (Euonymus fortunei var. Coloratus): PS to S
Forsythia Arnold Dwarf: S
Juniper horizontalis species: S
Hall’s Honeysuckle (Lonicera japonica Halliana): S to part SH
Manzanita Chieftan, Colorado, Panchito (Arctostaphylos): S to PS
Mountain Lover (Paxistima canbyi): part S to SH
Pawnee Buttes Sand Cherry (Prunus besseyi Pawnee Buttes): S
Rose Shrubs (Rosa spp.): S
Snowberry and Coralberry (Symphoricarus species): SH to part S
Sweet Autumn Clematis (Clematis paniculata): S
Sumac Autumn Amber (Rhus trilobata Autumn Amber): S
Sumac (Rhus aromatica Grow-Low): S
Herbaceous groundcovers
Ajuga, Carpet Bugle (Ajuga reptans): SH to S
Common Periwinkle, (Vinca minor): part PS to SH
Creeping Jenny, Moneywort (Lysimachia nummularia): S to SH
Creeping Phlox (Phlox subulata): S
Kannah Creek Buckwheat (Eriogonum umbellatum var. aureum): S to PS
Germander (Teucrium chamaedrys): S to part SH
Gold on Blue Prairie Zinnia (Zinnia grandiflora Gold on Blue): S
Hardy Geranium (Geranim spp.): S to part SH
Himalayan Fleeceflower, Border Jewel (Persicaria affinis): S to part SH
Orange Carpet Hummingbird Trumpet (Zauschneria garrettii): S
Pachysandra, Japanese spurge (Pachysandra terminalis): SH
Rockcress (Arabis spp.): S
Spotted Dead Nettle (Lamium maculatum): SH
Stonecrop (Sedum spp): S
Thyme (Thymus spp.): S to part SH
Veronica Snowmass (Veronica x P018S): S to PS
Wild Strawberry (Fragaria spp.) S to PS
Ornamental grasses (3 feet and under)
Blonde Ambition Blue Grama (Bouteloua gracillis Blond Ambition): S
Caterpillar (Harpochloa falx Freeda): S
Hardy Fountain Grass (Pennisetum alopecuroides spp): S
Indian Rice Grass (Achnatherum hymenoides): S
Japanese Forest Grass (Hakenochloa macra Aureola): SH
Little Bluestem (Schizachyrium scoparium): S
Prairie Dropseed (Sporobolus heterolepis): S
Sedge (Carex spp): S to SH
Silver Bluestem (Bothriochloa saccharoides): S
Undaunted Alpine Plume Grass (Achnatherum calamagrostis): S to part SH
Undaunted Ruby Muhly (Muhlenbergia reverchonii): S
Betty Cahill speaks and writes about gardening in Colorado. Visit her at http://gardenpunchlist.blogspot.com/ for more gardening tips.
