In Kent, where I live, in some areas of the North Downs chalk lies just inches under the surface. Small pieces of white soft stone can be found in the soil. The soil ‘soup’ - water with plant nutrients dissolved in it – is alkaline. Our chalky soils usually have flint and some clay in them. The clay makes them hard in a dry summer and sticky in a wet winter. So, what to do for a beautiful garden?
1. Improve the soil
This means adding as much organic matter as you can. Use garden compost, farmyard manure or shop-bought soil conditioner. Dig it in where you can, or spread thickly on the surface of established borders between plants, and let the eartworms take it down. A top-up every year in spring will be needed. Overtime, the soil will become darker, more fertile, and will hold on to water much better in summer.
2. Feed and water
If you cannot add masses of organic matter, give your plants additional feed. Any general fertilizer applied in spring and again in early summer will help. Chalky soil can dry out rapidly so keep an eye on it, particularly if you have just planted something.
3. Grow chalk-loving plants
These are especially adapted to chalky conditions and will thrive in such soil, especially if improved as above. A few examples are: carnation, allium, aster, cranesbill, hellebore, heuchera, peony, buddleia, daphne, lilac, olive tree. Many other plants are chalk-tolerant.
4. Grow your chalk-haters in pots
Azaleas, rhododendrons and a few others become sickly and die prematurely if planted in alkaline soil. Grow them in containers, in ericaceous compost, watered only with lime-free rain water.
Euphorbia robbiae thrives on chalk