What To Plant On Steep Slopes For Wyoming Landscaping

Steep slopes pose special challenges across Wyoming’s varied landscapes: erosion from spring runoff and summer storms, thin or rocky soils, strong sun and wind exposure, wide temperature swings, and low summer rainfall at many elevations. Choosing the right plants and planting patterns not only keeps slopes attractive, it prevents soil loss, reduces maintenance, and increases slope safety. This guide lays out practical, plant-by-plant recommendations for Wyoming slopes, plus proven installation and maintenance techniques you can use on small residential hillsides or larger property banks.

Key Principles for Planting Steep Slopes in Wyoming

Successful slope planting in Wyoming follows a few non-negotiable principles. Apply these before selecting species or laying out the design.

• Use deep, fibrous or spreading root systems to bind soil and reduce surface runoff.
• Favor drought-tolerant and cold-hardy plants suited to the local microclimate and USDA hardiness zone (most Wyoming sites range from zone 3 to 6).
• Prefer native or well-adapted regional species; they establish faster, need less water, and support local ecology.
• Plant along the contour to slow water flow; create mini-terraces or check structures where necessary.
• Limit the use of heavy mulch or topsoil that can slide; use erosion-control fabrics, coir logs, or rock mulches where appropriate.
• Plan for staged establishment: initial erosion control, fast-establishing cover, then longer-lived shrubs and grasses.

Best Plants for Wyoming Slopes

Below are plant groups and specific species that work well on steep Wyoming banks. For each plant listed include common name, a short description of why it is appropriate, sun and soil preferences, and spacing guidance.

Grasses and Grass-like Plants (Primary Stabilizers)

Grasses form dense fibrous root mats and are the backbone of slope stabilization. Use bunchgrasses and sod-forming grasses that tolerate drought, wind, and cold.

• Thickspike wheatgrass (Elymus lanceolatus): Deep-rooted, drought tolerant, forms tight sod; good for erosion control. Full sun, well-drained soils. Space 12-18 inches.
• Bluebunch wheatgrass (Pseudoroegneria spicata): Native bunchgrass with deep roots and good drought tolerance. Full sun to light shade. Space 12-18 inches.
• Western wheatgrass (Pascopyrum smithii): Sod-forming, excellent on foot slopes and drier clay soils. Full sun, tolerates some saline soils. Space 12-18 inches.
• Blue grama (Bouteloua gracilis): Short, warm-season grass useful on dry, south-facing slopes. Full sun, poor soils. Space 12 inches.
• Needle-and-thread (Hesperostipa comata): Native bunchgrass for rocky, well-drained slopes; long roots help bind soil. Full sun. Space 12-18 inches.

Low Shrubs for Stabilization and Structure

Shrubs add woody roots, intercept rain, and provide winter structure. Choose low, spreading types for steep terrain.

• Mountain mahogany (Cercocarpus spp.): Deep roots, excellent drought tolerance, long-lived; works on rocky sites. Full sun. Plant 6-10 feet apart.
• Serviceberry (Amelanchier alnifolia): Native, moderate size, fixes slope with strong root system and provides seasonal interest. Full sun to part shade. Plant 6-10 feet apart.
• Snowberry (Symphoricarpos albus or S. oreophilus): Spreading, good bank cover and erosion control. Tolerates cold and poor soils. Plant 4-6 feet apart.
• Skunkbush sumac (Rhus trilobata): Mat-forming, drought-tolerant, good for steep dry slopes; spreads by roots. Plant 4-8 feet apart.
• Rocky Mountain juniper (Juniperus scopulorum): For larger slopes adding vertical structure; evergreen and drought-tolerant. Space 8-15 feet depending on size.

Groundcovers and Mat-forming Plants

Groundcovers help reduce splash erosion and establish quickly in gaps between grasses and shrubs.

• Kinnikinnick (Arctostaphylos uva-ursi): Evergreen, forms mats on alkaline or rocky soils. Excellent for sunny, dry slopes. Space 18-24 inches.
• Sedum species and stonecrop (Sedum spp.): Succulent groundcovers for very dry, sunny slopes or rocky crevices. Plant outcroppings and pockets.
• Creeping thyme (Thymus serpyllum): Drought-tolerant, low, aromatic mat for sun-exposed slopes; tolerates light foot traffic. Space 8-12 inches.
• Native sedges (Carex spp.): For cooler, moister micro-sites like north-facing slopes or draw bottoms. Space 12-18 inches.

Perennial Flowers and Accents

Perennials add seasonal color and habitat value without compromising stability when combined with grasses and groundcovers.

• Yarrow (Achillea millefolium): Native, tough, spreads slowly; sits well among grasses. Full sun. Space 12-18 inches.
• Prairie coneflower / Gaillardia (Gaillardia aristata): Long bloom season, tolerates dry soils. Full sun. Space 12-18 inches.
• Penstemon (native penstemon spp.): Deep roots, drought tolerant, excellent for rockier slopes and pollinators. Space 12-18 inches.
• Lupine (Lupinus argenteus): Fixes nitrogen and provides early color; works with grasses on slopes. Full sun. Space 12-18 inches.

Trees for Large Slopes (Use Sparingly)

Trees are useful on large slopes for windbreak and additional root reinforcement, but avoid dense tree cover which can increase runoff concentration and snow accumulation problems.

• Limber pine (Pinus flexilis): Native to higher elevations, windfirm, deep rooting.
• Bur oak or other drought-tolerant natives: Plant widely spaced to avoid concentrated runoff and windthrow.

Plant trees at least 15-25 feet apart and avoid massing them on the steepest parts of the slope.

Planting Techniques and Installation Steps

Correct planting technique is as important as species choice. Use this step-by-step approach for initial installation on steep slopes.

1. Assess: Map slope grade, aspect (north vs south), soil type, and erosion risk. Identify existing desirable vegetation to keep.
2. Stabilize first: On bare or eroding slopes install temporary erosion control – coir or jute erosion blankets, wattles, or straw mulch anchored with staples. These reduce soil loss while plants establish.
3. Improve planting pockets: Create small bermed pockets or shallow terraces on the contour to hold planting medium and moisture. Avoid top-heavy soil fills that can slide.
4. Plant a mix: Combine quick-establishing grasses or seed for cover with plugs of deeper-rooting bunchgrasses, shrubs, and groundcovers. Use seed mixes with at least two to three grass species plus native forb seed for diversity.
5. Mulch and anchor: Use rock mulch or light gravel on very steep, dry slopes. For soil mulches, use coir mats to hold mulch in place. Do not use thick wood chips alone on steep angles because they can slide.
6. Irrigate carefully: Use temporary drip irrigation or soaker lines along the contour for the first 1-3 seasons, then wean to follow natural precipitation patterns.

Watering, Maintenance, and Establishment Timeline

Establishment is the most maintenance-intensive phase. Anticipate 1-3 growing seasons depending on species and site.

• Watering: Newly planted shrubs and grasses need regular deep soakings for the first 1-2 seasons. Water less frequently but deeply to encourage root growth. On hot, dry south-facing slopes, plan weekly deep watering the first summer if natural rainfall is limited.
• Weed control: Remove invasive annual weeds during the first year to reduce competition. Hand pulling or spot herbicide in extreme cases.
• Mulch and erosion checks: Check erosion control fabrics after major storms, and refill any eroded pockets. Re-anchor if displaced.
• Pruning and thinning: Prune only if necessary. Avoid heavy pruning that reduces root growth.
• Monitor for wildlife and rodents: Use protective tree guards for young shrubs if voles or rabbits are a problem.

Design Considerations by Aspect and Slope Severity

Adjust species and technique based on exposure and slope steepness.

• South- or west-facing steep slopes: Use the most drought-tolerant grasses (blue grama, wheatgrasses), sedums, kinnikinnick, and shrubs like skunkbush sumac. Rely on rock mulch or coarse gravel to reduce evaporation.
• North- or east-facing slopes: Allow slightly more moisture-loving species such as sedges, serviceberry, and larger bunchgrasses. Plant denser to take advantage of extra soil moisture.
• Very steep slopes (>50% grade): Maximize contour planting, use coir logs or terraces, and favor mat-forming groundcovers and low shrubs. Avoid large soil loads.
• Gentle slopes (less than 30%): You can incorporate a broader palette including small trees and larger shrubs spaced to allow understory grasses.

Practical Takeaways and Checklist

• Prioritize deep-rooted native grasses as the base stabilizer.
• Combine quick cover seed with plugs of bunchgrasses, shrubs, and groundcovers for long-term stability.
• Anchor soil with erosion control blankets, coir logs, or wattles during establishment.
• Plant on the contour and create small bermed pockets rather than adding heavy topsoil that could slide.
• Provide supplemental deep watering for the first 1-2 seasons, then transition to native precipitation patterns.
• Use rock mulch or gravel on hot, steep slopes; avoid loose woody mulches that can move downslope.

Troubleshooting Common Problems

• Persistent erosion after planting: Check for gaps in contour planting, inadequate groundcover, or missing erosion control fabric. Add wattles, re-seed with a fast cover crop (annual rye for temporary cover), and re-anchor blankets.
• Plants dying back in first season: Verify watering schedule–plants need deep, infrequent waterings early on. Check rootball depth and planting pocket soil quality.
• Invasive weeds dominating: Remove before they set seed, and consider reseeding with a denser native mix. Mulch and competition from established grasses will reduce recurrence.
• Rodent browsing or girdling: Install small hardware cloth collars around vulnerable shrub trunks and use repellents where appropriate.

Planting steep slopes in Wyoming requires attention to soil, water, exposure, and plant root habits. With the right mix of native grasses, groundcovers, and low shrubs, plus proper contouring and erosion controls, you can create a resilient and attractive slope that reduces maintenance and protects your landscape for decades.