Banks and slopes are often;

• Difficult to access
• Prone to erosion
• Prone to soil drying
• Often overrun with weeds

To help stabilise the soil and give speedy coverage, strong-growing climbers or ground-cover plants are required.

Thorough preparation and careful planting are particularly important, as soils on banks and steeper slopes are often poor and sandy. Remove all perennial weeds and add well-rotted manure or garden compost where possible.

A suitable soil test (RHS Soil Analysis Service) will help identify the soil texture and acidity or alkalinity which will influence the range of suitable plants.  Acid-loving or ericaceous shrubs grow best in a pH range of 4-6, and ideally pH 5-5.5.

On steeper slopes coarse coconut matting or similar material can be pegged down so that the soil on the slope, temporarily cleared of vegetation, is less likely to wash off. Plant through the matting. As the matting decays, stem-rooting plants should root-in to provide good consolidation.

Make watering easier by planting individual plants on a small horizontal shelf of soil – this way the water won’t run straight off. Thoroughly water-in plants to settle the soil around the roots after planting. Apply a general fertiliser such as growmore (or in March following autumn planting), followed by a mulch if possible to help conserve moisture during the summer months. Keep a regular check on watering needs throughout the first growing season, including the winter months with evergreens.

Deciduous:

Achillea millefolium - Native to GB and Ireland
Hydrangea anomala subsp. petiolaris AGM
Jasminum nudiflorum AGM
Neillia incisa 'Crispa'

Evergreen:

Ajuga reptans ‘Catlin’s Giant’ – Cultivar of Native to GB and Ireland 
Arctostaphylos uva-ursi 'Vancouver Gold': acid soils only. Cultivar of Native to GB and Ireland 
Calluna vulgaris: acid soils only. Native to GB and Ireland
Ceanothus thyrsiflorus var. repens AGM
Cotoneaster
Euonymus fortunei ‘Dart’s Blanket’
Euphorbia amygdaloides var. robbiae - Variety of native to GB and Ireland
E. amygdaloides ‘Purpurea’ - Cultivar of native to GB and Ireland 
Gaultheria shallon: acid soils only
Hedera colchica AGM, H. colchica ‘Dentata Variegata’AGM
H. hibernica AGM - Native to GB and Ireland
Hypericum calycinum
Lonicera japonica ‘Halliana’AGM
Mahonia repens
Rubus ‘Betty Ashburner’, R. tricolor
Thymus pulegioides ‘Aureus’ - Cultivar of native to GB and Ireland 
Thymus serpyllum ‘Pink Chintz’ - Cultivar of native to GB and Ireland
Vinca major
Vinca minor - Native to GB and Ireland (Archaeophyte)

Suggested planting distances 90cm-1.2m (3–4ft) apart. Space closer on poor soils and in difficult situations. In good conditions effective cover should be achieved after two growing seasons.

Links

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It is neither usually realistic nor safe to maintain close-mown grass on a steep bank or slope. However, in a less formal setting long grass can be a good option. There are several ways to achieve this;

• Sow direct onto bare soil with either a conventional lawn mix or a wildflower perennial meadow mix
• On very steep sites sowing may not be an option. Instead try wildflower turf (for example MeadowMat from Enviromat or Wildflower Turf) or a seed-impregnated biodegradable mat
• Enhance existing grass by planting up with wildflower plug plants and/or bulbs suitable for naturalising such as crocus, snowdrops and many narcissus