Begonia Cultural Information for Homeowners
The begonia world is so diverse that there are begonias that will grow in a wide variety of environments. Many varieties are well adapted to indoor culture. Some with little effort, others need more exacting conditions.
At PlantSmith Nursery we are constantly working to find and produce begonias that are easy to grow indoors without special care.
While there are many classifications of begonias, you can put most of the indoor types into 4 categories. The rhizomatous group, the angel wing or cane group, the rexes, and the shrub group. Of these four groups, the cane and the shrub can be the easiest to grow, with the rhizomatous being slightly more demanding and the rexes being the more finicky. The rex begonias we have selected are easier to grow than many older rex varieties.
Light:
Begonias do best with lots of light, however exposure of more than an hour or two of direct sunlight will burn the leaves of most varieties. We find that placing the plants in a north window in summer works well. In winter you can usually place the plants near any window without a problem, unless you live in the southern U.S. begonias that need more light become weak and stretched; begonias that receive too much light look stunted and burned. Begonias also do well under fluorescent grow lights. We find that many begonias grow fine outdoors in summer as long as they are not exposed to direct sun for more than a couple of hours.
Outdoors, direct sun can be tempered by installing shade cloth or lath structures over sunny areas that you wish to grow begonias.
Watering:
Many begonias are native to tropical areas, but none of them like to be constantly soaked. Begonias in rain forests, live in trees, or in very well drained organic matter with lots of air near the roots. In other words, it is fatal to over water your begonias. It is better to err on the side of being a little too dry, rather than a little too wet. If you place a saucer under the pots to catch excess water, be sure to empty the saucer and don’t let the plant stand in water for any length of time. As a general rule, I like the surface of the soil to be dry to the touch before I water the plants.
Pots and Soil:
Clay pots are ideal for begonias because they breathe. This allows more air into the soil and near the roots. Plastic pots are often used however and are fine as long as the soil is very porous. Almost any high quality commercial potting mix is acceptable if additional perlite is added. I like to use something like three parts Miracle Grow potting soil and 1 part perlite. Begonias hate to be over potted. If you have a plant that never seems to dry out, it may be in too large a pot. In other words, they prefer for the pot to be a little small rather than a little large. They actually like to be root bound. I do like to repot at least every 2 years, in order to get some new soil around the roots. Sometimes I even replant into the same pot but remove a little soil from around the root ball and replace it with fresh potting soil.
Fertilizer:
When your plants are actively growing, you should fertilize them ever couple of weeks. Use any good soluble fertilizer that you add to water and apply at half the recommended strength. Many begonias grow much slower in the winter and need very little if any fertilizer. Some begonias, especially some rexes and thick stemmed begonias will even loose their leaves in winter. They are not dead; they are just resting. Let them remain rather dry and don’t fertilize. When they resume growth in a couple of months, begin watering and fertilizing normally.
Humidity:
Begonias do best in 30% humidity. If necessary mist the plants occasionally or grow over pebble trays.
Pruning and trimming:
Begonias grown indoors can be pinched or pruned any time of the year. Any plants you bring indoors from outside will probably adjust easier if you trim them back. This will also give you cuttings to start a back up plant in case your plant doesn't do well with the change of conditions.