Gardening on slopes poses unique challenges, such as soil erosion, poor water retention, nutrient loss, and difficulty in root anchorage. These issues arise due to gravity pulling soil downhill, increased wind exposure, rapid water runoff, and exposure to harsh weather conditions.

To overcome these challenges, selecting the right plants is crucial for creating a stable and thriving slope garden. In this article, you’ll learn about some of the best plants for controlling erosion on slopes. You’ll notice that the best performers tend to be strappy, grass-like monocots with a robust fibrous root system. Add shrubs and trees with deeper roots to synergistically improve conditions dramatically.

The erosion control statistics you see in this article were tested by Todd Layt and Ian Paananen in 2007 https://www.ozbreed.com.au/best-plants-for-erosion-control/.

This slope is on a roadside, which means it probably doesn’t have much of a maintenance budget. The best-looking plant is definitely the strappy Tanika™ Lomandra, in the middle of the slope, which is doing a much better job of outcrowding weeds than the dry grasses below.

Ideal Plant Characteristics

• Robust Root Systems: Plants with deep, fibrous roots are essential for stabilising soil on slopes. These roots help anchor the plants and prevent erosion by holding soil layers together.
  
  
• Groundcover Capability: Covering the soil with above-ground growth can protect the soil from sun, wind, and rain, reducing erosion and maintaining moisture levels. They act as a protective blanket without sliding down the slope like mulch.
  
  
• Tolerance to Harsh Conditions: Choose plants that tolerate dry and sunny conditions. Drought and heat-tolerant species are better suited for slopes, which often experience dry conditions more frequently. On the other hand, varieties which are tolerant of wet feet are sometimes better for the bottoms of slopes, particularly in depressed areas.
  
  

Specific Plant Recommendations

Breeze™ Dianella caerulea ‘DCNC0’ PVR

Breeze™ Dianella is a tidy, tough ground cover plant ideal for erosion control. Unlike common varieties, it lacks messy canes, making it perfect for both commercial and residential landscapes. It thrives in full sun to part shade and tolerates humidity, cold, and moderate drought. Breeze™ Dianella strengthens the soil by 297%.

• Size: 60-70cm high x 60-70cm wide
• Planting Density: 4-6 plants per m²
• Care: Water as needed until established; prune every 3-8 years for best appearance.

Little Jess™ Dianella caerulea ‘DCMP01’

Little Jess™ is a dwarf Dianella with a clumping growth habit and short compact canes. It is highly drought-tolerant and produces purple flowers from September to November. It provides a 181% improvement to soil stability.

• Size: 40cm high x 40cm wide
• Planting Density: 6-10 plants per m²
• Care: Prune every 2-8 years; ensure the crown is not below soil level.

Little Rev™ Dianella revoluta ‘DR5000’ PVR

Little Rev™ Dianella is known for its compact blue-grey foliage and excellent architectural form. It requires little maintenance once established, making it a great choice for modern landscapes. It improves soil stability by 161%.

• Size: 30-40cm high x 30-40cm wide
• Planting Density: 6-10 plants per m²
• Care: Prune every 3-5 years as needed.

Evergreen Baby™ Lomandra longifolia subsp. exilis ‘LM600’ PVR

Evergreen Baby™ is a compact, fine-leaved evergreen Lomandra that is both drought and wet feet tolerant. It works well in sandy loam to heavy clay soils, contributing to its erosion control capabilities of 210%.

• Size: 40-45cm high x 40cm wide
• Planting Density: 4-8 plants per m²
• Care: Minimal pruning every 3-5 years; periodic watering during dry spells.

Lomandra longifolia ‘KATRINUS DELUXE’ PVR

Katrinus Deluxe is an improved form of Lomandra with stunning yellow flowers and a compact form. It strengthens the soil by 366%, making it a reliable choice for erosion control.

• Size: 70cm high x 70cm wide
• Planting Density: 2-6 plants per m²
• Care: Prune after 7 years if needed; avoid trimming in drought conditions.

Nyalla™ Lomandra longifolia ‘LM400’ PVR

Nyalla™ Lomandra features a fine leaf blue-grey form and provides excellent erosion control, strengthening the soil by 328%. It is resilient to coastal conditions and salt-laden winds.

• Size: 80-90cm high x 80-90cm wide
• Planting Density: 2-5 plants per m²
• Care: Minimal trimming; fertilise in spring or autumn.

Shara™ Lomandra longifolia subsp. exilis ‘ABU7’ PVR

Shara™ Lomandra is a compact form with blue-grey tones and yellow flowers. It is highly drought-tolerant and strengthens the soil by 225%, ideal for humid landscapes and mass plantings.

• Size: 45-55cm high x 50cm wide
• Planting Density: 4-6 plants per m²
• Care: Prune every 3-10 years; ensure the crown is above soil level.

Tanika™ Lomandra longifolia ‘LM300’ PVR

Tanika™ Lomandra is known for its soft evergreen foliage and drought tolerance, suitable for borders and mass planting. Its roots provide significant erosion control, at 250% compared with bare soil.

• Size: 70-90cm high x 70-90cm wide
• Planting Density: 2-4 plants per m²
• Care: Prune as needed every 3-10 years; avoid wet feet.

Strategies for Maintaining Slope Gardens

• Terraforming: Create stepped levels (terraces) on the slope to slow water runoff and reduce erosion, or dig bunds into slopes. Follow the age-old guidance of “slow the flow” of water.
• Ground Covering: Use ground-covering plants on steep slopes. Mulch will generally slide down unless there are plants to catch it. Geofabrics can help prevent erosion while plants establish – consider an organic product that will break down over time.
• Regular Inspection and Maintenance: Monitor for signs of erosion or plant stress; use drip irrigation to prevent erosion.

Conclusion

By implementing these strategies and plant choices, you can effectively manage erosion, improve water retention, and create a thriving, stable garden on slopes. Always consult local growers and horticulturists for specific regional advice to ensure the best results.