Begonias are ornamental flowering plants commonly used in both residential and commercial landscapes. These shade-loving plants grow well both outdoors and indoors as a houseplant. There are currently more than 1,000 different varieties of begonias available, yielding blooms in a variety of colors, including white, pink, red, yellow and orange. A variety of problems can affect begonias.
Begonias are susceptible to Xanthomonas leaf spot, a bacterial disease that causes speckling of the leaves and marginal necrosis of the plant. The best method of prevention is to make sure new plantings have not already contracted the disease and to use drip irrigation to prevent over-saturation of the soil. Overly wet soil conditions promote the growth of the bacteria.
Begonias frequently contract a number of fungal diseases, including botrytis blight, myrothecium leaf spot, pythium root rot, rhizoctonia aerial blight, and southern blight. Fungal diseases each have their own symptoms, but typically they can cause discolored leaves, premature leaf drop, root rot, stunted growth, and fewer blooms. Because fungus grows quickly in warm spring conditions and excessively moist soils, begonias should not be over-watered. Watering begonias in the morning or using drip irrigation can help prevent fungal disease. Diseased areas should be pruned promptly and disposed of. After each cutting, shears should be sterilized to prevent the spread of the disease. Any diseased leaves which have fallen should also be removed and disposed of.
Problems Caused by Pests
Begonias planted outdoors are frequently damaged by a number of pests, including aphids, fungus gnats, mealybugs, mites, shore flies, snails, slugs, thrips, whiteflies, and caterpillars. These pests can cause small to large holes in the foliage of the plant. They may also severely damage stems and roots, causing the plant not to flower to its full potential. The severity of the damage caused by pests depends upon the pest population of the plant. There are many pesticides available that treat each of these pests effectively.
Promoting Healthy Indoor Growth
Begonias are commonly used as potted houseplants. To achieve the best results indoors, begonias should receive 150 to 500 foot candles of light and should be planted in an area that receives at least 30 percent humidity. Begonias are typically purchased in pots 3 to 8 inches across, depending upon the size of the plant at the time of purchase. When starting the plants from tubers, start this procedure indoors one month prior to the last frost of the season. Tubers should be planted in a pot that contains a 50-50 mixture of perlite and moist peat moss. This process yields the best results when the plant is in a dark room at 70 degrees Fahrenheit.
Promoting Healthy Outdoor Growth
Begonia plants prefer shaded areas outdoors and requite moderate care when planted in ground-level flower beds, pots, or hanging baskets. These plants are susceptible to damage caused by frost and should not be planted until after the last frost of the season. When planted in beds, the top 8 to 10 inches of soil should be treated with peat moss and a fertilizer should be added at the time of planting. Keep begonias healthy with a monthly application of fertilizer. Begonias grow best in well-drained soils and at a temperature of 62 to 85 degrees Fahrenheit.