If you have begonias you love, make them multiply. Here's how.
Always begin with a good medium for propagating, such as a mix of one-half perlite to one-half peat, and pack it down in a broad plastic container to create a flat, even surface. Sprinkle water on the medium, but don't saturate -- the soil should be evenly moist throughout.
Take a leaf cutting, treat the tip of the leaf petiole with rooting hormone, and plant the stem in the soil. You can also roll the leaf into a funnel shape before planting it. This keeps the humidity of the leaf cutting stable. You can also make perpendicular slits in the major veins of the leaf and lay it down flat on the medium, firmly planting the hormone-treated stem of the leaf in the soil. Place small rocks on the leaf (not over the slits) to keep it anchored. This will result in several new plants growing from one leaf. Dividing one leaf up the middle of the stem and planting the two halves will also produce new plants.
Sever a one- to three-inch piece with at least one leaf attached from the parent plant with a razor. Nestle the cutting in the moistened medium.
Simple Propagating How-To
1. Cut a leaf, and place it cut-side down into a container filled with 4 parts perlite and 1 part potting soil.
2. Use a pencil or dibble to push soil around the leaf cutting (about 1/2 inch deep) and ensure good contact with the potting medium. Keep in a brightly lit, relatively humid environment out of direct sun, such as in a greenhouse or under a plastic cover.
3. Mist three or four times a day; water when the medium feels dry. The leaves will take root, create shoots, and, when a few leaves grow from the shoots, they'll be ready for repotting.