Giant begonias, also called cane or angel wing begonias, can grow to 6 feet high in containers, and up to 15 feet high in the ground in frost-free areas. These plants are some of the easiest begonias to grow, and can live for many years in pots with proper care. They typically have upright, cane-like stems with intermittent swollen nodes, and are grown for their large attractive leaves as well as their clusters of white, pink or red flowers. They thrive with bright, indirect light, rich soil and ample moisture. Giant begonias are easily propagated by stem cuttings.
Select a strong, 1/2 inch diameter cane with at least four nodes from a healthy plant. Try to find a cane with nodes spaced wide enough apart so that the entire four-node cutting will be about 1 foot long. You can propagate giant begonias any time of year, but they will root faster in spring and summer months.
Cut the stem diagonally just beneath the fourth node with the sharp knife. Remove the lower leaves, leaving at least one healthy pair of mature leaves attached near the top of the cutting.
Dip the bottom 2 to 3 inches of the cutting in rooting hormone immediately. You can use powdered or liquid rooting hormone, with or without fungicide.
Bury the cutting 4 inches deep in a 6-inch pot filled with well-draining potting mix and firm the soil gently.
Water the newly potted cutting well, and then keep it evenly moist, but not too wet, until new growth appears. Do not overwater giant begonias because they are susceptible to rot.
Place your cutting in a sheltered place, in partial shade until it is well rooted. In most cases, this should take one to two months.