Wax begonias are a beautiful plant, but because of the tiny, dust-like nature of their seeds, they can be a challenge to sow. Wax begonias need to be started indoors, as the seeds are tiny and the plants are delicate when they first germinate. You should plan to do this in January if you want to enjoy the blooms in the summer. While many floral markets start their begonias from cuttings, if you enjoy gardening and are up for a challenge, sow wax begonia seeds.
Fill your seed containers with sterile potting soil, available from a nursery or garden center. Water when filled. Make sure that your seed containers are in a tray, so that you can water them from the bottom in the future.
Sprinkle one or two begonia seeds onto the wet soil in each pot. You may lightly tap the seed, but do not cover it with dirt. The master gardeners at Cornell University recommend leaving the seeds exactly where they fall onto the soil.
Cover the seed container with a sheet of plastic wrap. This will help trap in moisture and increase the temperature, keeping the seeds warm. Water the seeds from the bottom of the container. Most seed pots have holes in the bottom for drainage and watering. If you water from the top, the seed itself can become too wet, which can cause fungal damage.
Place the seed containers in a light location, but not in direct sunlight. A temperature of 65 to 70 degrees is ideal for germination, which should occur in approximately seven days.
Remove the plastic covering from the seedlings when they become tall enough to press against it.
Transplant the seedlings to larger pots when they have at least four leaves. It can take months of indoor growing before begonias are ready to be transplanted. Do not plant outdoors until after the last frost has taken place for your growing zone.