You'll often hear this being talked about by gardeners, especially at this time of year: but what is it, and why do we do it? There are various theories about…
They grow best in a cool moist, fertile soil with partial shade although they will tolerate full sun. They may need staking.
Divide every third year in the autumn or late winter.
Pests, diseases or disorders
Watch out for aphids and fungal stem rot.