Wax begonias will bloom in the spring all the way through the summer. A perennial, often gardeners treat them as annuals because the begonia will not tolerate frost and needs to be brought indoors during the winter. All begonias have a tendency to form fungal and bacterial diseases if they do not receive proper ventilation and air circulation. Space your wax begonias properly to reduce the risk of infection.
Most series and cultivators of wax begonias will reach the height and spread of 6 to 12 inches when fully mature—although some may grow a couple inches taller depending on the growing conditions such as sunlight and soil. Wax begonias usually stay inbounds in a garden setting and do not spread, as do many other types of perennials. Spacing should be done at planting time to insure adequate growing room.
If you plant wax begonias in a flower bed, space them 8 to 12 inches apart so that ideally—when fully mature—they will still have a small space between each plant to avoid overcrowding, according to the Clemson University Extension. Extra dwarf varieties can be planted about 6 inches apart.
Wax begonias in containers can be spaced a bit closer, but no more than 7 to 8 eight inches. Use larger containers instead of trying to cram two or three plants in a small space; they will not receive proper air circulation and will not thrive as well—plus you may have to deal with unwelcome complications such as fungus.
Botrytis, powdery mildew, stem rot and leaf spots are common problems with begonias. Overcrowding your plants will lead to an unhealthy environment—such as darkness and high humidity—that fungus and bacteria will thrive in. Always remove debris at the base of your begonias for better air ventilation and keep dead blooms and leaves away to discourage spreading. At the first sign of powdery mildew or any other fungal infection, increase the air circulation by thinning out your plant and using a fungicide safe for begonias.