Chalky soils: plants for

Chalky soils are alkaline, so will not support ericaceous plants that need acid soil conditions. Very chalky soils may contain lumps of visible chalky white stone. Such soils cannot be acidified, and it is better to choose plants that will thrive in alkaline conditions. Many chalky soils are shallow, free-draining and low in fertility, but variations exist, and where there is clay present, nutrient levels may be higher and the water holding capacity greater.

Chalky soils: plants for

Quick facts

Top 5 plants for chalk:
Agapanthus
Campanula
Clematis
Delphinium
Lavandula

Introduction

When planting on chalky soils it is important to first establish how deep the topsoil is. Many trees and shrubs that will tolerate alkaline soil conditions may become chlorotic (yellow) on shallow soils over chalks. In some gardens the soil layer may be very thin indeed – only a few inches – before hitting solid chalk. Where this is the case, topsoil will need to be brought in to make planting possible. On shallow soils over chalk where increasing soil depth is not an option, wildflower mixes selected for chalk tolerance may still thrive.

Practical considerations

When planting on chalky soils;

  • Break up the chalk to a depth of 75cm (30in) so that plant roots can spread out and establish
  • Whether bringing in new soil or improving existing soil, add plenty of well-rotted organic matter such as garden compost, composted green waste or farmyard manure
  • Smaller plants get established more quickly than more mature specimens
  • Mulch plants with organic matter to conserve moisture
  • Attention to watering will be required for a longer period than with other soil types as plants on chalky soils may take several seasons to establish and are more prone to drying

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