Category: Soil, Compost & Mulch Read time: 8 min read

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8 min read Easy Read Best read in Summer
Chalk soilSandy soilBuckinghamshireBerkshireBedfordshire

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Published

13 May 2026 · 8 min read

Last reviewed

19 July 2026

Reviewed by a senior CGM team member.

The short answer

Quick Answer

Chalk soil is alkaline (pH 7.5 to 8.5), free-draining and often shallow. Plants that thrive: lavender, rosemary, salvias, alliums, beech, yew, clematis and most Mediterranean plants. Plants that struggle: rhododendrons, camellias, blueberries, heathers and other acid-loving plants. Improve chalk soil by adding organic matter and growing acid-loving plants in pots of ericaceous compost.

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What Is Chalk Soil?

Chalk soil is formed from the calcium carbonate remains of marine organisms. It is alkaline (pH 7.5 to 8.5), free-draining and often shallow (sometimes only 10 to 20cm deep over solid chalk). The Chiltern Hills are made of chalk, so gardens in High Wycombe, Amersham, Princes Risborough, Wendover, Stokenchurch and surrounding areas have chalky soil.

What Grows Well on Chalk Soil

Herbs and Mediterranean plants

  • Lavender, the classic Chiltern plant, loves chalk
  • Rosemary, evergreen, drought-tolerant
  • Salvia, long-flowering perennial
  • Thyme, low-growing ground cover
  • Sage, evergreen culinary herb

Flowering perennials

Shrubs and trees

  • Photinia, red new growth in spring
  • Choisya, evergreen, scented flowers
  • Pittosporum, evergreen structure
  • Roses, thrive on chalk if well fed
  • Beech, the classic Chiltern hedge
  • Yew, formal hedges, long-lived

Climbers

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What Struggles on Chalk Soil

Acid-loving plants cannot tolerate the high pH of chalk soil. They will go yellow (chlorosis) and die. These include:

  • Rhododendrons, need pH 4.5 to 6.0
  • Camellias, need acid soil
  • Pieris, needs acid soil
  • Blueberries, need pH 4.5 to 5.5
  • Heathers (most varieties), need acid soil

If you want to grow these plants on chalk soil in the Chilterns, grow them in large pots of ericaceous compost and feed with an ericaceous plant food twice a year.

How to Improve Chalk Soil

Add organic matter

Chalk soil is often thin and low in organic matter. Add a 5cm layer of compost or well-rotted manure each spring and dig it in. This improves water retention and adds nutrients. See our soil improvement guide.

Mulch annually

A 5cm mulch of bark or compost in spring suppresses weeds and retains moisture. Chalk soil dries out fast in summer, so mulch is essential for gardens in High Wycombe, Princes Risborough and Wendover.

Water in summer

Chalk soil drains freely, which means plants can suffer in dry summers. Water newly planted specimens regularly through their first summer.

Grow in raised beds

For plants that need deeper soil or different conditions, build raised beds and fill with topsoil. This gives you control over the soil without having to replace the chalk.

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Testing Your Soil

Test your soil pH with a simple kit (5 pounds from a garden centre). If the pH is above 7.5, you have chalky soil and should choose plants accordingly. See our guide to the best plants for chalk soil for more recommendations.

Get Help with Your Chalk Soil Garden

If you have a garden on chalk soil in the Chilterns and need help with planting or soil improvement, contact us on WhatsApp.

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Further Reading

Estate Note

In established gardens, soil structure takes decades to build. Avoid deep cultivation near mature trees and shrubs, as their fine feeder roots extend well beyond the canopy.

Relevant local areas

This advice is particularly relevant to gardens in these areas.

Useful next steps

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.

Open the plant planning toolOpen guide Low-maintenance plants for Chiltern gardensOpen guide Best plants for chalk soil in the ChilternsOpen guide
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Sources and citations

This article draws on the following sources. Specific claims are cited inline where relevant.

  1. CGM field records (2024-01. Site observations from gardens across Oxfordshire, Buckinghamshire, Berkshire and Bedfordshire.
  2. Royal Horticultural Society (2024). RHS Gardening Advice and Plant Finder. Available at rhs.org.uk.
  3. Met Office (2024). Regional climate averages, South East England. Available at metoffice.gov.uk.
  4. British Geological Survey (2024). Soil parent material data for the Chilterns and Thames Valley. Available at bgs.ac.uk.