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Quick Answer
To improve soil around mature trees and hedges: mulch annually with compost or bark, water in dry spells, feed in spring, avoid digging (which damages roots), and plant ground cover to suppress weeds. The soil around mature trees and hedges is often dry and depleted because the roots take up water and nutrients. In the Chilterns, this is particularly pronounced on chalky soils.
The Challenge of Mature Trees and Hedges
Mature trees and hedges are valuable features of a garden, but they create challenging conditions for other plants. The roots of mature trees and hedges take up water and nutrients from a wide area, leaving the surrounding soil dry and depleted. The shade from the canopy further limits what can grow. The result is often bare, dry soil under trees and hedges.
In the Chilterns, where mature beech, oak, and yew are common, this is a familiar problem. The chalky soils are already dry, and the tree roots make them drier. But with the right approach, you can improve the soil and grow plants under mature trees and hedges. This guide explains how.
Why Soil Around Mature Trees Is Poor
- Root competition: tree roots take up water and nutrients
- Shade: the canopy blocks light, limiting plant growth
- Dry conditions: the soil is often dry, especially on chalk
- Low organic matter: the tree roots break down organic matter fast
- Compaction: the area under trees is often walked on
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How to Improve the Soil
1. Mulch Annually
Mulch is the single best thing you can do for soil under trees and hedges. Apply a 5 to 10cm layer of compost or bark mulch annually. This:
- Retains moisture
- Adds organic matter as it breaks down
- Suppresses weeds
- Protects tree roots from compaction
Do not pile mulch against the tree trunk, as this can cause rot. Keep a 10cm gap around the trunk.
2. Water in Dry Spells
The soil under mature trees is dry because the tree roots take up the water. Water the area deeply once a week in dry spells. Apply 25mm (2.5 litres per square metre).
3. Feed in Spring
Apply a balanced fertiliser in spring. Use growmore or blood, fish and bone at 50g per square metre. Water in if no rain within 2 days.
4. Avoid Digging
Digging around mature trees damages the roots. Instead, mulch and let the worms do the work. The worms will incorporate the mulch into the soil over time.
5. Plant Ground Cover
Plant ground cover plants that tolerate dry shade. These suppress weeds and add organic matter as they grow. Good choices:
- Epimedium, evergreen, dry shade
- Bergenia, large leaves, dry shade
- Ivy, evergreen, dry shade
- Pulmonaria, spring flowers, dry shade
- Hardy geraniums, some varieties tolerate dry shade
- Ajuga, low growing, tolerates dry shade
Plants for Dry Shade Under Trees
For chalky Chiltern soils under mature trees:
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How to Plant Under Mature Trees
- Choose the right plants: plants that tolerate dry shade
- Plant in autumn: when the soil is moist and the trees are dormant
- Plant small: small plants establish better under trees
- Plant between roots: do not cut tree roots. Plant in the gaps.
- Water regularly: for the first year, water weekly in dry spells
- Mulch after planting: 5cm of bark or compost
Cost of Improving Soil Under Trees and Hedges
| Item | Cost (per 10 sqm) |
|---|---|
| Compost or bark mulch | 50-100 pounds |
| Fertiliser | 5-10 pounds |
| Ground cover plants (20) | 100-300 pounds |
| Planting labour | 50-150 pounds |
| Total | 205-560 pounds |
Common Mistakes
- Digging around mature trees. This damages the roots. Mulch instead.
- Not mulching. Mulch is essential for soil under trees.
- Planting thirsty plants. The soil is already dry. Choose drought-tolerant plants.
- Planting too close to the trunk. Keep a 30cm gap around the trunk.
- Not watering new plants. New plants under trees need regular watering for the first year.
Frequently Asked Questions
Will grass grow under mature trees?
Poorly. Grass struggles in shade and dry soil. Better to plant ground cover or mulch the area.
Can I grow vegetables under trees?
No. Vegetables need sun and fertile soil. Trees provide shade and take up nutrients.
How often should I mulch under trees?
Annually, in spring. Apply 5 to 10cm of compost or bark. Keep a 10cm gap around the trunk.
Get Help Improving Soil Under Trees
If you have mature trees or hedges in Oxfordshire, Buckinghamshire, Berkshire or Bedfordshire and want help improving the soil around them, send us a WhatsApp with photos and we will aim to respond within 12 to 36 hours, Monday to Sunday.
Further Reading
- How to mulch properly
- How to improve soil before planting
- Best evergreen shrubs (some tolerate dry shade)
On mature hedges, always check for nesting birds before cutting. The bird nesting season runs from March to August. Assess previous pruning history to avoid cutting into old wood that may not regenerate.
Put this advice into practice
Use the relevant CGM tool or follow a related guide, then send us a few photos if you would like a tailored plan.
Sources and citations
This article draws on the following sources. Specific claims are cited inline where relevant.
- CGM field records (2024-03. Site observations from gardens across Oxfordshire, Buckinghamshire, Berkshire and Bedfordshire.
- Royal Horticultural Society (2024). RHS Gardening Advice and Plant Finder. Available at rhs.org.uk.
- Met Office (2024). Regional climate averages, South East England. Available at metoffice.gov.uk.
- British Geological Survey (2024). Soil parent material data for the Chilterns and Thames Valley. Available at bgs.ac.uk.