Chalky soils have a degree of acidity (pH) greater than 7. They are called basic or alkaline. Below this, the degree of acidity is said to be neutral (6.5 to 7) or acid (pH <6.5).
Light in colour, they may have chalk mixed with stones or flint. You can test for chalky – or alkaline – soil by diluting a sample in white vinegar. The calcium carbonate in chalky soil will fizzle and bubble in reaction to the vinegar.
In the garden, a chalky soil, rich in fine particles can be sticky, compacted and constrictive in winter; and hard, dry and cracked in summer. The overabundance of calcium ions (Ca++) in the soil can block other positive elements and provoke chlorosis which results in a yellowing of leaves: green veins and pale-green to yellow blades. These include iron (Fe2+), manganese (Mn2+) and boron (B3+).
However, one quality of these soils is that they warm up quickly in spring, so if you add organic matter and fertiliser, you can grow a wide range of plants in them provided that:
If the pH is highly alkaline and if acidifying a soil is not an option for you, then you will only get good results with calcium-loving plants.
Below, you will find a list of perennials suitable for growing in chalky soil.
Source: Chalky Soil (Royal Horticultural Society)
Five months' flowering!
Blue-black trumpet flowers
THE NEW STAR
With a touch of purple
Flowers non-stop throughout the summer
A great favourite!
A florist's aster
Heat waves or winter cold, nothing bothers it.
Great, a story!
A remarkable cultivar for any good garden soil.