Site and soil preferences
Geraniums thrive in most soils, unless extremely waterlogged. While most grow in sun or dappled shade, others, such as G. phaeum and G. nodosum, thrive in deep shade.
Buying and planting
When buying geraniums, look for plants with plenty of leaves and shoots growing from the base. They can be planted at any time, but spring and autumn are ideal.
With specimens in shades of blue, pink, maroon and white, geraniums can be used in most colour schemes. One of their most useful qualities is an ability to form attractive, floriferous ground cover, even in the deepest shade. The best for this is G. macrorrhizum, which spreads by underground rhizomes and eventually forms an impenetrable mat that suppresses most weeds.
Most species die down in the autumn, when their old foliage and stems can be cut back to encourage a crop of fresh leaves in spring.
A light scattering of a general fertiliser around plants in the spring keeps them happy all year.
Most geraniums are easily propagated by division in the spring. But some, such as G. wallichianum 'Buxton's Variety', pose problems because the stems tend to go back to a small rootstock. The best solution is to propagate by seed, although this may produce offspring that vary slightly from the parent.
Geraniums with trailing stems, such as G. 'Ann Folkard', can be propagated by spring cuttings using the new side shoots. Remove each cutting above a node, where the leaves are attached, and cut about 2.5cm (1in) off the bottom to leave a bare stem. Then insert the stems in pots or trays of cuttings compost. The cuttings should be watered in, covered with polythene and placed in a shaded glasshouse or cold frame.
Hardy geraniums are trouble-free and resist most pests and diseases. White, powdery mildew may occasionally affect G. pratense later in the year, but cutting back the plant to ground...