Tuberous begonias may be the showiest of all annuals and perfect for part-shade; it’s little wonder they elicit such joy. I cannot imagine a garden without showing off several of these beauties in containers. This year, 2020, I am attempting to propagate two of the tubers: the white one shown above and a large red one I have in the front that bloomed continuously from May to October. I was delighted to discover the pink tips on the white begonia. In the store it was blooming pure white. And while bright red is not my top choice for colour, it was all the store had at the time. I have been rewarded with non-stop blooms that have brightened my front porch for two consecutive seasons.
It wasn’t until a conversation I had with a friend that I learned that this family of plants is a very large and diverse one. This blog entry was an opportunity to learn more about them.
The National Gardening Association Plants Database reports a record of 2,463 images of 15,878 begonias. The Begonia genus includes more than 1,800 plant species, all native to tropical or subtropical regions. Most are perennial plants in zones 10 and 11, but they are widely grown in almost every region as annuals. There is enormous variation in the genus. Begonias cross readily and include everything from durable landscape plants to delicate specimens. Today’s vivid specimens are hybrids descended from begonias that Victorian botanist Richard Pearce collected in the South American Andes in the 1880s. He found B. boliviensis, B. veitchii, and B. pearcei, which European hybridizers crossed to create a dizzying array of varieties–with frilly petals, ruffled petals, picotee petals, double petals, single petals–as well as a group of camellia lookalikes.
Begonias are terrestrial understory herbs native to tropical regions around the world, including Central and South America, Asia, and Africa. Begonia foliage can resemble ivies, ferns, aralias, grasses, and peperomias. Leaves can be flat, pebbled, shiny, hairy, fuzzy, or spiralled. Flowers are in all colors but blue, and can be found growing as tiny single blossoms growing out of a stem to foot-wide clusters of hundreds of tiny flowers to giant double blossoms ten inches or more in diameter.
Most begonias in cultivation are hybrids, so they cannot be grown from seeds. Fortunately, however, they readily reproduce from leaf cuttings or rhizome division. I saved the instructions to try at home. Hardy to zone 10–11, they are generally grown as an annual, attain a height of 12 to 16 inches and prefer part shade to shade.
Sources divide garden begonias into a few groups. Of interest to me are:
(1) the cane type are grown from straight, sometimes brittle stems and are prized for both their blooms and their foliage. They include angel wing and dragon wing begonias. very popular and beautiful angel wing and dragon wing begonias are cane-type begonias. These hybrids generally feature clusters of pendant flowers that appear throughout the year. Their roots are fibrous. The leaves tend to be round and waxy, and relatively small. The flowers are also fairly small, about 1 1/2 inches;
(2) semperflorens are the common wax begonias because of the waxy appearance of their leaves available in pink, white, and red, in single or double blooms;
(3) Tuberous begonias primarily grown for their flowers. They have a short dormant period in the fall and winter. They include trailing types and upright plants. This group has the most spectacular flowers, large blooms in neon-like shades of pink, yellow, orange, red, or white. They have a fleshy, round tuberous root like a potato and generally bloom in mid-summer through fall. The tubers are often planted as annuals each year, or they can be dug up and stored indoors for the winter. The trademarked Nonstop series from Proven Winners is the preferred tuberous begonia for regions with hot summers. Most tuberous begonias like moderation in all things, including light, water, and fertilizer, but this series is heat tolerant. If you remove the spent blossoms on Nonstop begonias and allow the plant to put its energy into more blossoms instead of seed production, you can achieve a mass of flowers;
(4)Trailing begonias are great for hanging baskets. They feature pendant growth with beautiful displays of flowers, sometimes year-round. Most pendant begonias have bright-green leaves
Begonias like light, well-drained soil and morning or late-afternoon sun; direct, hot sun can burn the foliage and flowers. Too much shade can cause them to grow spindly. Grow begonias in bright, shady areas out of direct mid-day sun. Most varieties do well with direct morning sun or dappled sunlight all day long. The bedding semperflorens (wax) type can be grown in direct, daylong sun.
Good ventilation results in good growth. Optimum temperatures range from 55 degrees at night to about 85 in the day. As to extremes, some can survive short bouts of freezing, and others can withstand intensely hot summers. Higher humidity (through fine misting) helps them grow better in higher temperatures.
The soil mix should be slightly acid containing loose, well-draining ingredients such as perlite, vermiculite, and sphagnum peat and/or leaf mold. The soil should become neither excessively dry nor allowed to stay sopping wet. Well-draining soil is optimal. Plants should be watered thoroughly when the top of the mix becomes dry to the touch. With their shallow root systems, begonia prefer shallow pots made of either clay or plastic.
Feed begonias after you see flower buds. Use a weak solution of a low-nitrogen/high-phosphorus fertilizer at two-week intervals. Most growers prefer to water with dissolved fertilizer of ¼ recommended strength at each or every other watering, although time release types which stay on the mix surface offer good results. This gives a better supply of trace elements and micro-nutrients. Never fertilize a dry, dormant, or sick plant.
Prune in late winter, early spring when new growth starts. Pinch growing tips (soft-pinching) throughout the growing season to shape plants, fill them out, and keep them within bounds. Tuberous begonias have male and female flowers. Pinch out the single female blooms so plants can put more energy into the petal-filled double male flowers.
Begonia stem rot and mildew are caused by the same fungus. Fortunately, you can control both by watering only the soil and not the foliage, letting the soil dry between waterings, and providing good air circulation. Pinch off brown, water-soaked stems or leaves. The same goes for white mildew patches. Then spray right away with a fungicide if desired.
https://www.whiteflowerfarm.com/gardening-videos (search for begonia video)
https://www.begonias.org (American Begonia Society)