Many flowering perennials can be increased now by taking stem-tip cuttings (use healthy, non-flowering shoots about 10 centimetres long). These include penstemon, erysimum, centaurea, aster, argyranthemum, fuchsia, osteospermum and pelargonium. Trim each cutting below a leaf joint, remove the lower leaves and insert several cuttings into a pot of damp cuttings compost (mix one part sand or fine grit with one part soil-less potting compost). Cover with a clear plastic bag to create a moist atmosphere. Place out of direct sunlight in a warm place and remove any rotted leaves that may appear. In a few weeks, they will have rooted and can be potted on.