1,500 Species of Begonia
Begonias are native to moist tropical and subtropical regions of all continents except Australia, and are most diverse in South America. There are over 1,500 known species, ranging from rhizomatous perennials a few inches high to 10 foot shrubs. Many are grown indoors as house plants, prized either for their beautifully coloured and textured foliage or showy flowers, sometimes both present in the one species or cultivar.
Mostly evergreen, they have broad, usually asymmetrical leaves or rather brittle and waxy texture. Female flowers, as distinct from male flowers which are on the same plant, have broad, colored flanges on the ovaries which develop into winged fruits.
Begonia enthusiasts divide the species and cultivars into a number of classes depending on growth habit and type of rootstock.
The cane stemmed begonias are erect growers, sometimes quite tall, with straight stems, fibrous roots, and usually pendant clusters of showy flowers; somewhat similar are shrubby begonias, with a more closely branched (the bedding begonias belong here); another similar group but with lower softer stems are known as the winter flowering begonias grown for their profuse and colorful flowers that peak in winter.
The rhizomatous begonias are a larger and varied class, with leave arising directly from creeping knotty rhizomes – they include the Rex begonias with colorfully variegated leaves and many others grown for foliage; and finally there are the tuberous begonias, now largely represented by hybrids of the Tuberhybrida Group: These plants die back to tubers in winter and bear large, showy, often double flowers in summer.
Many of the cane stemmed, winter flowering, shrubby and rhizomatous types can be grown outdoors in frost free climates and make fine garden plants, though rhizomatous kinds in particular are prone to slug and snail attack. As indoor plants they do well in standard potting mix with peat moss or leafmold added to increase acidity.
Grow in bright to moderate light, with good ventilation and above average humidity, which can be maintained by standing pots on a tray of pebbles and water. Pinch back young plants of the shrubby type to keep them compact and to encourage flowers.
Tuberous begonias require special treatment; tubers must be forced into growth in early spring at a temperature of 65F in peat moss or sphagnum, and kept in a cool, well ventilated green house for the summer flowering season. After flowering plants die back and tubers are lifted in mid-fall and stored dry.
Propagate from tubers in the case of tuberous begonias. Other begonias may be propagated from stem or leaf cutting (layer the cut leaf blades flat on damp sand and weighing them down with pebbles), or by division of rhizomes, or from seed.
Begonias are susceptible to gray mold, powdery mildew and botrytis in the warmer part of the year if conditions are too damp.