All Cane-Like and Shrub-Like begonias develop thick stems. However, there is one group in which the stems are thick from base to tip from the early stages of growth, and these are called thick-stemmed. Some of the plants may grow quite tall, to two metres or more, but most are of medium height, around one metre. They are unusual and are grown mainly by the collector. They have been much used to produce interesting and beautiful hybrids.
These tall-growing begonias need ample room, whether as garden or pot plants. When grown in pots it is essential to provide at maturity a large, deep pot to provide stability and ample room for root development. Potted thick-stemmed begonias may be used as house plants or in courtyards where they need a very well-lit position with some direct sunshine in the mornings but not hot afternoon sun A lack of sunlight will result in sparse flowering and development of lanky growth.
Young plants are best grown in small squat pots being gradually potted on as they develop. Restricting the pot size will have the effect of controlling the plant size. Pots or garden plans need free-draining garden soil or potting mix and regular fertilising.
A wide range of temperatures is suitable with some types able to tolerate a wider range than others. The optimum is 18º C to 22º C. In very cold weather they will cease growing and may in some cases become almost dormant. Leaf loss is not a worry in these conditions as the plant will leaf up as soon as warmer weather arrives.
With many of the thick-stemmed begonias branching ins not normal but tip pruning during the early stages of growth will encourage this, producing a thicker and more pleasing plant. Tip pruning of old growth is not recommended – it is better to remove old stems completely thus encouraging new ones to develop from the roots.
Water as for other begonias, and never allow them to stand in water or slushy soil or potting mix. Fertilising is most important to ensure good strong growth of the stems.
Propagation: The thick-stemmed begonias may be propagated from seed, stem cuttings or leaves. Place the cuttings in good light, but not direct sunlight. Once a good root system has developed the cuttings are placed in small, squat pots and fertilising is commenced, using a water-soluble fertiliser.
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