Gardener's Corner

Division

Bulbs and corms increase naturally by forming clumps of smaller bulbs or cormlets that draw food from the parent plant. It is simple to propagate theses by splitting the plants. Many garden plants produce young that they become overcrowded; competing for space, light and moisture, new bulbs often fail to flower rendering them blind. Division keeps them healthy and strong. Some bulbs such as Cardiocrinum giganteum take years to flower only to die when they do. Lillium candidum, Crocus tommasinianus, nerines and some sternbergias flower best if they are congested; divide them only to increase your stocks. Most bulbs have a dormant period, and are best divided just before the onset, after the foliage has died down, however many can also be divided just before the onset of growth. Evergreen bulbs and corms such as dieramas, cyrthanthus and lloydias, should be divided immediately after flowering. The period of dormancy varies, depending upon the species' native climate. For example, a crinum is dormant in spring, a snowdrop in summer, and a tulip until late summer.

Most offsets form within the parent bulb's skin, or tunic; they are attached to the basal plate, from which the roots grow. Some bulbs, daffodils and lilies, produce their offsets to the sides of the parent. In the case of tulips, the offsets are directly beneath. The size of the offsets will vary. Care should be taken when lifting parent bulbs or corms. Offsets, which are close in size to the parent bulb, can be expected to flower the following year, and can be planted into their flowering position.

1. In spring before active growth begins, lift a clump of bulbs with a garden folk. Shake of any excess soil from the roots. Pull the clump apart and select large healthy, well-developed offsets. Discard any that are withered, misshapen or show signs of disease.

2. Pull or cut the offsets carefully from each bulb, taking care to preserve the roots. Dust damaged basal plates with a fungicide.

3. Prepare a 15cm (6in) pot with a moist, sandy compost. Pot each offset individually, up to its neck. Label and water the pot.

1. Lift a clump of mature bulbs. Select the healthy bulbs, and reject those that are dead or diseased.

2. Separate any pairs or clumps of bulbs with large offsets into single bulbs by gently pulling them apart, without damaging the roots.

3. Clean the bulbs by rubbing them with finger and thumb to remove any loose, outer tunics. Dust the bulbs with fungicide.

4. Pot or replant the divided bulbs. Plant the bulbs at twice their own depth, and space them at least their own width apart.

For more information the RHS 'PROPAGATING PLANTS' book tells you all about individual species that you may want to propagate from.

Ruthe Gray