Choose large modules, or small pots. Half fill each with compost consisting of one-third finely shredded bark, one-third vermiculite and one-third potting compost. Water well.
Choose a large pot-grown plant, remove the pot, then saw the rootball in half. Repot one half, using fresh compost. The remaining half can then be divided to give masses of root cuttings.
Cut off the top growth from your cuttings and prune the hairy roots so that each cutting fits in a module, taking care not to damage the creeping rhizome - the engine of next year's crop.
Firm into the module, cover with more compost to just below the rim, water lightly, label, then place in a cold greenhouse or cold frame. Only water again to prevent the compost from drying out completely.