In early autumn, dig up mature plants from the garden using a fork, divide them into smaller pieces with your hand or a hand fork. Shake loose as much of the soil from the roots as possible. Replant the divided pieces into pots or trays of potting compost and water well. Cut back the top-growth.
Keep in a light place and free from frost and draughts. This way they will produce fresh shoots over the winter that may be harvested regularly.
Discard forced plants in spring or plant them out in the garden. If planted out do not pick their leaves for at least a season to allow them time to recover vigour.
Evergreen herbs, such as winter savory, thyme and rosemary may be gathered throughout the year, but limit winter harvesting as there is no new growth at this time.