Begonias love a warm, moist environment. Indoor air can be drier than the plants prefer, so mist them or run a humidifier near them to increase humidity.
Avoid over-watering, as too much water leads to root rot. Check the soil regularly and water only when it feels dry to the touch.
All types of begonia thrive when the soil is consistently moist. Use a rich, well-draining compost or organic mulch to boost the soil’s natural moisture content and to buffer temperature extremes. Apply a balanced water-soluble fertilizer once a month during the growing season to promote vigorous growth. For best results, avoid overwatering. This causes the plant to become stressed and susceptible to disease and pests, especially bacterial leaf spots. If a begonia begins to wilt, check the level of moisture in its soil. If it’s dry, water it, but only until the soil is thoroughly moist.
In fall and early winter, tuberous begonias need to be gradually brought inside for overwintering. Stop watering the plants in late summer to early autumn, trim back their foliage and dig up the tubers before frost. Store the begonia tubers in a warm location, out of direct sunlight, until spring. Be sure to sterilize the digging tools and storage container before placing them in a new container of well-draining soil.
A balanced fertilizer will help your begonia plants look healthy and thrive. If you are growing rhizomatous begonias (such as painted-leaf or fancy-leaf varieties), amend the planting bed at planting time with a 2- to 3-inch layer of compost or pine bark humus to improve soil aeration and help it retain moisture, advises Clemson Cooperative Extension.
Begonia flowers can become brown and faded, especially if they’re not getting enough humidity. If you see this, keep the plant in a well-lit location and run a fan next to it for more air circulation. You can also prune off the brown and faded flowers to encourage new ones to grow.
If you’re propagating begonias from seed, start them indoors in early spring or fall, in a sterile seed starting mix. Wax begonias such as ‘Dragon Wing’ are easy to root from stem cuttings, while tuberous begonias such as ‘Big Ben’ and ‘BabyWing’ need a little more care.
Begonias thrive in cool temperatures and do best indoors during the summer, but you can gradually move them outside in spring once the chance of frost is gone. The plants require consistent soil moisture and moderate to bright light.
Plants that get too warm tend to lose their flower color. Keep indoor temperatures below 80 degrees Fahrenheit, and place a fan in the room to help keep air moving.
Prune dead flowers and faded foliage daily, or as needed. Doing so not only keeps your begonia looking tidy, but it reduces the chances of disease that can spread from rotting debris.
Use a clean pair of pruning shears or scissors and sterilize the blades with rubbing alcohol before each trimming. The fungus powdery mildew can spread quickly through begonia leaves, so be sure to spray the plants with a fungicide as soon as spots appear. Fungicides are typically available at garden centers, but they can also be purchased online.
Begonia plants enjoy a warm environment and some shade, depending on the variety. Direct sunlight can scorch the leaves and stems, especially with wax or cane begonias. To propagate begonias from leaf cuttings, remove a stem below a node and push the cut end into moist soil mix (a rooting hormone on the buried end increases the chances of success), firming gently to keep everything anchored in place. Then cover with a type of cloche to keep humidity high until small begonia plantlets form around the base of the leaf.
When a begonia begins to look faded and has white blotches on its leaves, it may be getting too much sun or the temperature is too warm. Move the plant to a brighter spot in the house or a shadier location outside to help it regain its color and vitality. Begonias also benefit from annual repotting in the spring. This allows them to grow more quickly than their tubers and encourages blooming.