Outside in the open ground, many herbs die back in winter, but you can prolong the season for some by potting up bits of them and growing them on in a conservatory or porch, or on a sunny windowsill. Herbs that produce new leaves from the base of the plant are good candidates for this treatment. Among them are chives, mint, parsley, lemon balm and tarragon. Choose healthy-looking plants, divide them and pot up the healthiest bits. Or buy new plants from a garden centre and put them in slightly larger pots. Give indoor herbs an occasional liquid feed to encourage them to produce new leaves, but don't expect them to make the same growth as they would in summer: autumn and winter light levels are too low.