Garden Design for Chalk Soils
Alkaline soil is common across Britain, especially in areas like the South Downs, and is mainly derived from limestone or chalk, so the soil is known as chalky. It generally has a pH factor of 7.1 or above. And, in fact, it’s something that millions of British gardeners have to contend with.
These soils tend to be shallow, free draining and stony, so gardening this type of land is not without its challenges. What’s more, if you add organic matter to the soil it can decompose rapidly, so that it is hard to keep fertile.
However, there are many examples of wonderful gardens made on chalky soil, such as the University Botanic Gardens at Cambridge, or the Hidcote Manor National Trust property at Chipping Camden, Gloucestershire.
And it’s not all bad news. Flooding is rare, given the porosity of this kind of soil, and it warms up quickly in springtime compared with kinds of ground. Equally, with a good quality fertiliser, and manure, you will be able to grow a wide range of plants. (Dig in lots of organic matter, and use mulch wherever possible.)
When creating your design, bear in mind that smaller plants will establish themselves more rapidly than species which are more mature. Plan to have plants which grow well in chalky soils. These include Mediterranean and prairie plants.
If you want camellias, rhododendrons and other plants, which tend to prefer an acidic soil, plan your design to have them in containers.
Here are some other ideas to include in garden designs for chalk soils:
The white Madonna lily loves chalk as do tulips and spring anemones.
Peonies thrive in this type of soil, but other ideas include euphorbia characias and oriental poppies.
Many of these, once they have flowered, die quite quickly. You will need to be prepared to shear them and fit in other plants to fill in the gap. An ornamental clover or perennial pea will do the job.
Leguminous plants also love chalk, as does the borage family.
When it comes to shrubs, you have plenty to work with planning out your design. Think lilacs, elders, or buddleia, while the Moroccan Pineapple Broom flowers against a warm walk in chalk soil.
In terms of a colour scheme, grey and silver leaved plants appear to adore chalky soil. Equally, many aromatic shrubs love the ideal drainage and warmth of chalk, so you can create a fragrant space.
Old Men’s Beard, or wild clematis, will thrive in alkaline soil – just make sure there is enough humus at the roots.
Flowering cherries and crab apples do well in soil with a high chalk content – indeed they probably do best in such conditions. Field maple is wonderful in autumn, when its leaves turn gold, while the Judas tree, or Cercis, flowers magnificently.
Especially if you add a lot of compost and manure, vegetables are excellent for chalky conditions, so you should get superb crops, year after year. (See our article about designing a vegetable garden.)
The key thing is that you work with the soil. Don’t try and fight it. Garden plants are very adaptable, and the soil will be more fertile the longer you work it, but you have to understand how chalky soil works, and how to look after it.