Begonia is one of two genera belonging to the family Begoniaceae; the other is Hillebrandia, a genus endemic to Hawai’i. Currently, approximately 1,900 Begonia species have been recognised, with native distributional ranges throughout the subtropics and tropics of Central and South America, Africa and Asia. The name Begonia commemorates Michel Bégon (1638-1710), Governor of French Canada and a patron of botanical exploration.
Begonias can be succulent herbs, sub-shrubs or climbers. The roots are fibrous or rhizomatous, or tuberous; species from the cooler Andes become dormant in winter. Begonias are monoecious, that is separate male and female flowers are produced on the same plant. Different groups of begonias are cultivated for the tremendous variation in their foliage and flowers.
Horticulturally, begonias are often grouped according to their type of growth or habit. Many species and cultivars are popular as house or garden plants in warmer climates. Begonia grandis ssp. evansiana is one of the hardier species, surviving temperatures of minus five degrees Celsius when dormant, so it can be grown outside in sheltered, well drained spots in the United Kingdom.
Begonia rex is a rhizomatous species from Assam, first introduced into cultivation in 1858. It has been used in breeding work with other Asian Begonia species to produce the Begonia Rex Cultorum Hybrids. Many Begonia Rex cultivars, such as ‘Fireflush’, ‘Fireworks’ and ‘Raspberry Swirl’, have marvellously decorated leaves. These hybrids are best grown at a minimum of ten degrees Celsius in a well-drained compost in semi-shade.
In contrast, tuberous begonias are mainly grown for their flowers, which can be staggering in both size and colour because of artificial breeding. It all started with the red, pendulous-flowered Begonia boliviensis, an introduction to Europe from Bolivia in 1864. Other species, such as the yellow-flowered Begonia pearcei and the large, red-flowered Begonia veitchii, soon followed. Tuberous begonias were widely used as bedding plants in the late 1800s and are still used today, being easily raised from seed. The enormous double flowers of pendulous varieties are shown off to great effect in hanging baskets, whilst upright varieties are more often used as exhibition plants.
Cane-stemmed begonias are another popular group, of which several types are grown at Oxford Botanic Garden. One of these is Begonia luxurians, a native of Brazil, also known as the palm-leaf begonia. It can have stems up to 1.5 metres tall with distinctive palmate leaves and large heads of creamy-white flowers.
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Tebbitt MC 2005. Begonias. Cultivation, identification and natural history. Timber Press.