Plants for chalky soils 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 perfectly possible to create a full and attractive border even in these sometimes challenging conditions

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Many plants thrive in a chalky soil
Many plants 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 to provide a variety of interest throughout the year. A simple planting plan helps to create depth, interest and good coverage in a border.

White and blue plants for chalky soil

© 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 enjoy healthier plants and lower inputs compared with trying to grow plants that are less well suited.

The Geranium provides some ground cover and will help prevent erosion of bare soil. The ground cover can also help to reduce evaporative moisture loss from the soil surface and suppress weed growth.

Additional organic mulching, preferably with homemade compost, can further improve soil moisture retention and weed suppression. Mulches should be spread when the soil is already moist, to help trap some of that moisture before it dries out in summer. 

1 - Viburnum x burkwoodii ‘Mohawk’
2 - Persicaria microcephala ‘Red Dragon’
3 - Choisya x dewitteana ‘Aztec Pearl’
4 - Geranium ‘Orion’
5 - Thalictrum ‘Black Stockings’
6 - Ceanothus ‘Skylark’
7 - Agapanthus ‘Midnight Star’
1 - Viburnum x burkwoodii ‘Mohawk’ is a deciduous shrub with glossy green foliage, which is felted white beneath and gains orange and red tints in autumn. The white flowers open from red buds and are strongly fragrant. 

2 - Persicaria microcephala ‘Red Dragon’ is a herbaceous perennial that provides dark purple foliage with a striking silver splash, and white flowers in late summer.

3 - Choisya x dewitteana ‘Aztec Pearl’ is a small evergreen shrub with bright green leaves, each comprising 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’ is a herbaceous perennial forming a spreading mound of deeply lobed green leaves. Sky-blue flowers with thin purple veins and a white eye are produced through the summer. 

5 - Thalictrum ‘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.

6 - Ceanothus ‘Skylark’ is an evergreen shrub with small glossy leaves, which becomes smothered in clusters of deep blue flowers in late spring to early summer.

7 - Agapanthus ‘Midnight Star’ is a striking hardy perennial with dark strap-like leaves and round heads of trumpet-shaped cobalt blue flowers with darker blue stripes in early summer.

About alkaline, chalky soils

Alkaline soil is common in areas of the country with a lot of chalk or limestone. By choosing plants that are well-suited to chalky or limey soils, you can keep your border looking good and growing well, because plants that are planted in the right place tend to be stronger and more naturally resistant to pests and disease.

Once the plants are established, this will also reduce the need for extra inputs that less well-adapted plants would need, such as fertilisers and frequent watering.
 

The challenge of growing on chalky soils

Chalky soils can be very fast-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 of chalky or limey soils can cause some minerals to be ‘locked up’ in the soil, leaving the plant struggling to take these up and grow. However, if the plants you choose 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. For more information about sustainable gardening, please see the RHS Sustainability Strategy.

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