Family: Begoniaceae

Native to tropical and subtropical regions, this genus comprises over 900 species. Many thousands of cultivars have also been produced and it is now possible to enjoy begonias throughout the year in many different climates, either indoors or out. Begonias can be divided into three main groups: fibrous-rooted and tuberous plants, which are both valued for their flowers, and rhizomatous begonias, mostly grown for their foliage. Begonias can be enjoyed as house plants, garden plants in suitable climates, or for seasonal bedding.

Species

Tuberous begonias are loved for their superb double flowers which bloom profusely in dazzling colours ranging through pink, rose, red, cerise, vermilion, salmon-orange, bronze, yellow, cream, white, and a combination of these shades. The modern, summer-flowering tuberous begonias, those known as B. x tuberhrybrida, have very large flowers - some growing to 30 cm (12 in) in diameter - and strong stems, and are resistant to disease. Some have frilled or ruffled petals; others have petals which are similar to those of hollyhocks, roses, camellias, carnations, and even daffodils.

Fibrous-rooted begonias, both summer-flowering varieties from B. semperflorens and winter-flowering varieties from B. socotrana, look pretty in garden beds and conservatories respectively. In addition to their brilliantly coloured flowers, they have attractive glossy foliage. Some are known by the name of wax-leaf begonias. Sometimes spotted or speck-led, they come in shades of deep green, bronze, dark red or yellow. The popular name 'angel wing' refers to the graceful leaf shape of some of the varieties. B. acutifolia has white flowers in spring. B. foliosa has white or rose flowers in summer. Var. miniata bears scarlet flowers in winter. B. incarnata has rose flowers in winter. B. scharffii's pale pink flowers bloom in winter. B. semperflorens cultivars produce pink, red or white flowers in summer. B. socotrana has produced many cultivars such as 'Gloire de Lorraine'. Tree begonias, also fibrous-rooted, make elegant pot plants and feature plants in the garden. Long-flowering shrubs with bamboo-like canes and handsome foliage, they do well in shady positions providing they receive ample moisture. Because they are shallow rooted, they can be grown successfully where there is not much soil. Plants that are recommended include B. coccinea and its cultivars.

Begonias grown for their foliage are usually cultivars of B. rex and are remarkable for the immense variety in their beautifully coloured and patterned leaves. Other species grown for their ornamental leaves include B. bowerae. The delicate green leaves are stitched with black at the edges. B. 'Cleopatra' has golden-green star points on chocolate brown. B. heracleifolia has deeply lobed leaves. B. maculata has spotted white leaves. B. masoniana, iron cross, has a dark purplish cross on each bright green leaf. The foliage of B. metallica has a metallic lustre, while B. sanguinea's is bright green on top, blood red underneath.

Cultivation

Tuberous begonias can be raised from seed, tubers or cuttings from new shoots on tubers. Seedlings require sterile soil, with a drainage layer in the bottom of the container, followed by a mixture of finely sieved loam, sand and peat in equal quantities. Sow the seed thinly over the surface and press very lightly into the soil. Water by standing the container in a tray of water until the moisture creeps to the surface. Cover the container with a sheet of glass or plastic and keep in a shaded, sheltered place. Don't cover the glass with paper or anything at all as begonias are one of the few plants that need some light to germinate their seed.

Seedlings should start to appear within two to four weeks. At this stage, prop up the glass with a wedge to allow some air to circulate. Don't remove the cover altogether until most seedlings have appeared and are growing well. Make sure that adequate shade and shelter are maintained. The seedlings should be pricked out into small pots or nursery beds as soon as possible.

If raising the begonias from tubers, the dormant tubers can be started in early spring by placing them, hollow end up, in trays of moist peat until the shoots appear. When the third leaf appears, transfer the tubers to individual 13 cm (5 in) pots filled with potting mix containing some peat. Keep the pots moist in a shady position, protected from frost and strong wind.

Alternatively, cuttings can be taken from newly sprouted tubers. Keep the strongest shoot which will become the main stem of the plant and cut out the lesser shoots as soon as established. Make a clean cut in the tuber just below the basal ring. Crowd the cuttings into a pot filled with propagating mix and keep them shaded and moist. When new growth is vigorous, transfer them to larger pots and eventually plant out in the garden in a suitable climate or use them as indoor decoration.

The display of potted begonias will be showier if the two small female flowers on each side of the more spectacular male flower are removed when small to direct energy into the larger bloom. Do not do this, however, if you wish to harvest seed.

Plant tubers or small plants in a well-drained garden bed in a semi-shaded position. They like a rich soil with plenty of humus. The crowns of the tubers should be no more than 12 mm (½ in) below the surface. Water well, but do not overwater in humid coastal areas. Do not feed tubers until they have formed roots, otherwise they will rot. Begonias should be fed only with organic plant food. Protect from the hot summer sun. Ideally, they should receive full sun until about 11 a.m., with about 70 per cent shade thereafter. Tuberous begonias should be lifted and stored during the winter but regular watering and feeding should continue into early autumn as the tubers must store food for the following season.

If in a frost-prone area, transfer bedding begonias to pots and keep them in a warm, sheltered position until mid-autumn. 'then reduce watering and allow the plants to dry off and die down. The stems can then be easily removed. Lift the tubers from the soil and clean them carefully, brushing away soil and taking care to remove any remaining stem which might cause them to rot. Dry on a rack out of the direct sun for several days until the tubers feel firm and hard. Store during winter on racks in a dry, airy spot or in pots filled with clean dry sand or peat.

Fibrous-rooted begonias are grown for summer bedding. They are raised from seed sown in early spring. They prefer temperate to warm conditions, damp soil and protection from excessively hot sun. They will be killed by frost so do not plant out until all danger of frost is over.

Rhizomatous begonias grow rapidly from rhizome cuttings, but a more popular methodof propagation is by leaf cutting. Propagate in spring and summer, choosing leaves with strong stems. Make a clean cut to the stem with a knife. Place the stem in an open mix of sand, peat and vermiculite, and keep in a warm, humid environment. Roots should develop within three weeks. Tufts of new leaves will appear where the stem joins the leaf on rex begonias, and at the end of the stem for other species. Another method is to cut some leaves into small pieces, scatter them on trays of peaty soil and keep in a humid environment. Adventitious buds will soon develop. Alternatively, cut a leaf into triangular slices, with a main vein running through the point of each slice. Plant the slices with the points about 5 mm (1/4 in) deep in a propagating mix of, for example, two parts sand and one part peat.

Rex begonias prefer a light, but rich, soil with plenty of humus. Perfect drainage is essential as they are very prone to root rot. Overwatering must be avoided. Keep soil moist but not soggy. If they dry out, they should revive quite quickly if the pot is soaked in water up to its rim until the whole root ball is soaked. Water early in the morning so that the leaves have a chance to dry during the day. If fungal diseases appear, remove and destroy the infected leaves and spray with a fungicide. Keep rex begonias in warm, draught-free spots out of direct sunlight. Old specimens can be repotted or top dressed in spring or summer, but be careful not to bury the rhizome too deeply. It should rest just on top of the soil. During winter, most rhizomatous begonias, including the rex varieties, go through a dormant phase when the leaves may look shabby and wilted, but they will recover in spring. Keep the soil fairly dry during this period and do not apply fertilizer.

Climate

Begonias are frost-tender and can be grown outdoors all year round only in zone 10 and above.