Care of Aconite (Monkshood)

I have just received your new catalogue, and what a selection! Last year I planted two monkshood (Aconitum napellus) plants, but they did not take. Do they need any special care? This year I want plant a greater selection of herbs and would like advice on what sort to plant. The soil in the garden is heavy clay, and faces south. I need herbs which can grow in such soil, and also can grow in the shade as well as full sun.

Aconite prefers deep, damp soil in shade. If the soil dries out in summer aconite will suffer. Your heavy clay soil should be okay, but it may be a good idea to work in some peat moss to improve the organic content of your soil and to help break up the clay. Aconite will also grow in sunny locations but the soil must be damp at all times.
If you are growing monkshood for medicinal purposes be aware that all parts of the plant are extremely toxic if ingested. Even handling the plant can cause poisoning. The plant is very important in herbal medicine as a painkiller and for its action on the heart and central nervous system. But it is dangerous and is only to be used by qualified practitioners.