Plants for chalky soil with white & blue flowers

Plenty of plants, of a variety of shapes, sizes and colours, thrive in the higher pH of chalky soil, so it's possible to create a full and attractive border even in these sometimes challenging conditions

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Many flowers thrive in a chalky soil
Many flowers thrive in a chalky soil

Quick facts

  • Chalky or limey soils can benefit from the addition of plenty of organic matter to improve water retention
  • Chalky soils drain quickly, even in wet weather, so can be good for Mediterranean plants
  • Some plants do their best colours in chalky soil

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The planting plan

James Lawrence, RHS Principal Horticultural Advisor, has designed this simple, attractive, and most importantly, sustainable, border design for you to try at home with plants that are easy to grow, widely available and look good together.
This white and blue planting design, provides a range of plants that once established will thrive in chalky or limey soil, while still providing a variety of interest throughout the year. A simple planting plan helps create depth, interest and good coverage in a border.

Chalky soil, white and blue

© James Lawrence

Choosing plants for chalky soil

These plants have been selected because their preferred growing condition is alkaline soil. By using plants that are naturally adapted to these conditions, we can reduce the potential problems that are more likely with plants which are less well suited.
The Geranium provides some groundcover and will help prevent erosion of bare soil. The groundcover can also help to reduce soil surface moisture evaporation and suppress weed growth. Additional organic mulching can further improve soil moisture retention and weed suppression.
Viburnum x burkwoodii ‘Mohawk’
Persicaria microcephala ‘Red Dragon’
Choisya x dewitteana ‘Aztec Pearl’
Geranium ‘Orion’
Agapanthus ‘Midnight star’
Ceanothus ‘Skylark’
Thalictricum ‘Black stockings’
1 - Viburnum x burkwoodii ‘Mohawk’ has glossy green foliage felted white beneath, which gain orange and red tints in autumn. The flowers open white from red buds and are strongly fragrant. 
2 - Persicaria microcephala ‘Red Dragon’ is a herbaceous plant which provides dark purple foliage with a striking silver splash and white flowers in late summer.
3 - Choisya x dewitteana ‘Aztec Pearl’ has evergreen and fragrant bright green leaves with 3-5 slender leaflets. The pink-tinged buds open to clusters of fragrant white flowers in late spring and often repeat in autumn.
4 - Geranium ‘Orion’ forms a spreading mound of deeply-lobed green leaves and has sky-blue flowers with thin purple veins and a white eye, produced through the summer. 
5 - Agapanthus ‘Midnight star’ has dark evergreen strap-like leaves and round heads of trumpet-shaped blue flowers with darker blue stripes, in early summer.
6 - Ceanothus ‘Skylark’ is a shrub which has small glossy evergreen leaves and becomes smothered in clusters of deep blue flowers in late spring-early summer.
7 - Thalictricum ‘Black stockings’ is a tall, herbaceous perennial with lacy foliage and upright, near-black stems bearing sprays of fluffy clear purple-pink flowers in summer. 

About alkaline, chalky soils

Alkaline soil is common in areas of the country with a lot of chalk or limestone.
By choosing plants which are well-suited to chalky or limey soils, you can keep your border looking good and growing well because, planted in the right place, plants tend to be stronger and more naturally resistant to pests and disease. Also, once established this will reduce the need for extra  fertilisers that less well-adapted plants would need, and fewer inputs such as water

The challenge of growing on chalky soils

Chalky soils can be very quick-draining so have the same issues as sandy soils in that respect. However the most important thing to bear in mind is that the high pH can make some minerals ‘lock up’ in the soil, leaving the plant struggling to grow. However if your plants have adapted to naturally thrive in those conditions, they will grow much better. 

Why choose a sustainable planting combination

Using the ethos of 'right plant, right place' to create a sustainable planting combination, is great for the environment. It helps avoid waste and the use of products and practices needed to try and help ailing plants, such as the application of fertiliser. It also creates robust, long-lived planting that benefits soil health and garden biodiversity.

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