This section is from the book "The Florists' Manual", by William Scott. Also available from Amazon: The Florist's Manual.
These are grown entirely for their very handsome foliage. We have used them largely in veranda boxes in shady situation, but to see them at their best they should be in large pots or pans in a warm shaded conservatory. They like a more humid atmosphere than any other class of begonias.
Well matured leaves should be cut up in November or as soon as you have good oottom heat in the sand (a stout piece of midrib should be with each section) and insert one inch in the propagating bed. Keep the sand moderately moist and in six or seven weeks small leaves will start from base of cuttings. Pot into 2 1/2-inch pots using a light soil with sand and leaf-mold. If the young plants are kept at a temperature of 60 degrees they will make good useful plants by end of May.