A bed of colourful begonias
Stem cutting of tuberous begonias are normally taken early in the year - and after the tuber has been forced into growth with gentle heat - much as is the requirement for starting tubers into growth for planting. The young growths are simply cut from the forced tuber and inserted into either single pots or by numbers into a seed tray or propagator. The cuttings will be no more than a couple of inches long at this stage, with barely a proper pair of leaves showing.
The cuttings should be slightly shaded, and not in direct sun. A sheet of milky which plastic will provide enough protection from directs sunshine. If you have such a bag, then the pots of cuttings can be placed inside and the bag tied closed to keep airtight.
Gentle bottom heat is the best growing conditions to get the stem cuttings to root. Once the cutting has rooted, then bring into open air in gentle stages to allow the cutting to acclimatise to the new conditions. Feed weekly with dilute liquid fertiliser to keep the rooted cutting growing well. this is particularly important, for the early start and good growing conditions are required in order for the new plant to produce a tuber - which is required for winter storage. Cuttings taken later in the year, will not produce a suitable tuber at the base, so are difficult to keep over winter.
The rooted begonia cuttings can be grown in the same as tubers in the normal way - either as young begonias in the garden, container or hanging basket.