The Rex begonias, which include the striking Begonia masoniana, are grown primarily for their handsome leaves as theare not very showy. These begonias have fibrous roots and should not be dried off at any stage. They need a greenhouse with a minimum temperature in winter of 10°C. (50°F.). with shade from strong sunshine in summer. They grow well on the greenhouse floor, just under the staging.
These begonias can be propagated from their leaves. The conventional method is to sever the leaf with a piece of stalk attached and then to slit the veins on the underside of the leaf with a sharp knife. It is then laid on the surface of a peat and sand mixture in a pan or shallow box. Small stones placed on the leaf help to keep the cut veins in contact with the rooting medium. Stood in a warm, moist propagating frame with a temperature of 16 to 18°C. (60 to 65°F.), rooting will soon take place where the cuts were made on the veins, and young plants will develop.
Another method is to cut the leaves into small squares and place them on a mixture of moist peat and sand in a shallow box. They are then treated as for whole leaf cuttings. The small plants which result are first moved to 2-in. pots and then to 3-1/2 and 5-in. pots. When the young plants are established in their final pots feeds with a liquid or soluble fertiliser will be helpful.