Bring on the Begonias

By Dawn Pettinelli, UConn Home & Garden Education Center

Begonias are not difficult to grow if you keep in mind where they come from. All begonias perform best in bright, indirect light although a few will tolerate full sun. Varieties grown for their foliage often have slightly lower light requirements. The intensity of light, however, will affect their foliage color. The brighter the light, the more vibrant their foliage. They prefer relatively high humidity which can sometimes be hard to provide them with when the furnace or wood stove is blowing out hot, dry air during the cold winter months. Try moving them to a more humid area like the bathroom or kitchen, grouping them together or setting them on pebble trays filled with water.

A potting mix for begonias should contain a fair amount of organic matter and most soilless mixes fit the bill. Begonias should be kept moderately moist. They can tolerate an occasional drying out, as you might expect if you feel their waxy or succulent leaves, but they abhor wet feet. Never let them sit in a saucer full of water. Adequate drainage is essential. They do best situated where temperatures do not go below 60 degrees F.

Begonias are primarily divided into three main classes although now quite a few interclass hybrids exist. All have both male and female flowers occurring separately on the same plant. The evergreen flowering type begonias include the most commonly grown bedding plant, the wax begonia. Wax begonias have glossy foliage in bright green, red-tipped green, maroon and bronze. Flowers come in pink, red and white and may be single or double. The seed is very fine, almost dust-like, and this plant is often easier to root by cuttings than seed. Simply insert them into a moistened sand and perlite mix. Double-flowered varieties are sterile and must be vegetatively propagated.

This group also includes the cane-stemmed which produces tall, bamboo-like stems but is exceptionally easy to grow. The 'Angel Wing' and 'Devil Wing' begonias fall in here. Most cultivars benefit from regular prunings. The shrimp begonia (Begonia limmingheiana) is a great candidate for indoor, winter-flowering, hanging baskets.

Tuberous begonias, as the name implies, are generally grown from tubers, although seed has been recently made available for some cultivars. I highly recommend pelleted seed for anyone wanting to try it. These begonias are renowned for their beautiful, large blossoms in shades of pink, orange, scarlet, yellow, salmon and white. The shapes of the blossoms also vary quite widely. Tubers are planted hollow side up with the top slightly above soil level.

Here in New England, if planted in mid-March, tuberous begonias will be ready to set out by Memorial Day, should begin bloom by the end of June, and will continue through first frost. Tuberous begonias go through a resting period each year. Whether growing a typical summer flowering tuberous begonia or the winter flowering, Lorraine or Christmas begonia, or even the Rieger or Elator begonia hybrids, they usually start to yellow after a long period of bloom. That is a signal to reduce watering, let the stems slowly wither and the tubers go into dormancy for a few months. I dig them from their containers, place them in a 5 gallon bucket and water them ever so slightly once a week to keep them from drying out. When I see little, tiny new eyes, I know it is time to start them for another season of bloom.

The third group of begonias is rhizomatous-rooted. These species and cultivars form a thick stem used for water storage during dry seasons in their native habitats. Perhaps the most popular of the rhizomatous rooted class are the Rex begonias, grown for their spectacular foliage. Leaves have a metallic sheen and come in colors such as pink, bronze, maroon, brown, black and red. Rex begonias are propagated by leaf cuttings. Several cuts are made on a leaf which is then placed flat on moist sand or vermiculite. Small pebbles can be set on top of the leaf to ensure contact with the medium. Cover with a plastic bag and keep moist. After several weeks, if temperature, light and moisture are adequate, new plantlets should emerge.

Those interested in begonias may want to look up the American Begonia Society at www.begonias.org. I have found quite a few interesting begonia cultivars and species at the CT Flower and Garden Show which will be held in Hartford in February. The UConn Home and Garden Education Center will be there too so bring your gardening questions and one-half cup of soil for a free pH test if you come. With weeks of wintry weather ahead, why not try some begonias to brighten up you windowsills and provide a promise of spring. If you want information about how to grow begonias or on any other gardening or home topic, call us, toll-free, at (877) 486-6271, visit our web site at www.ladybug.uconn.edu or contact your local Cooperative Extension Center.