One of the wonderful attributes of rhizomes, corms and tubers is that they are successful self-propagators, by creating both new growth below ground and seeds above.
Anyone who has planted a canna from what seems like a small rhizome in late winter will be amazed at the sheer quantity of root material that can be dug up the following autumn after just one summer’s growth – a mass of rhizomes all waiting to be divided and propagated. If that was not enough, some cannas are also generous producers of seed.
With corms the story is different. After flowering the old corm dies, and a new one forms on top of the old one, with clusters of cormlets around the sides. In this way some cormous plants, such as crocosmia, are able to form quite large clumps, which need to be divided every three years or so to prevent overcrowding and congestion. Cormous plants can also propagate themselves by seed – Crocus tommasinianus, for example, naturalizes well in late winter grassland where the grass is fine.
1. Take a sharp knife and cut the tuber (in this case a begonia tuber) through the middle so that each part has a shoot.
2. Dust the open cuts with a fungicide such as yellow sulphur powder. Prepare two small pots with moist potting compost (soil mix).
3. Plant both halves so that they sit firmly on top of the compost. Keep the compost moist and plant on when new growth is apparent.
Plants grown from tubers are also great survivors. Individual tubers grow to quite large proportions – surprisingly large compared with the tiny tubers on offer in the shops – and also produce generous quantities of seeds and shoots, which can be propagated. Leave a few Anemone blanda tubers planted in the eye of an old apple tree and within a few years it will be a mass of blue flowers as the seeds form new plants and the tubers plump up and grow. Cyclamen and Eranthis hyemalis are also generous seeders, both enjoying a position beneath deciduous shrubs or trees, where they will get plenty of moisture in winter. Eranthis hyemalis is usually quick to establish. Scatter seed in mid-spring and within just a few years you will have sheets of golden flowers in midwinter. For best results, soak cyclamen seeds for up to ten hours before sowing.
Begonia tubers can be divided in late winter or early spring if two shoots are seen on one tuber. They can also be propagated from cuttings taken from small shoots that have grown from the tuber in late winter or early spring. Dahlias can also be propagated from cuttings taken from new growth during the same periods.
Taking Begonia and Dahlia Cuttings
1. Gently pull a young begonia stem away from the tuber. A small piece of rooting material may well have come away at the base of the shoot.
2. Plant the new cutting into a pot of moist compost (soil mix) and grow on in warm conditions, out of direct sunlight, until the new plant can be planted out.
3. For dahlias, slice through the bottom of a stem and plant the cutting in moist compost. Place on a windowsill, out of direct sunlight, covered with a clear plastic bag until rooted.