The so-called cane-stemmed Begonia are tough heat- and drought-tolerant plants that can form quite substantial shrubs 1-3 m tall, although there are many cultivars that are more compact and grow to a height less than 1 m. They all comprise a thicket of slender, upright bamboo-like stems, clothed with lush, lop-eared leaves that are attractive all year round and are ideal for a tropical-style garden. Some forms have deeply cut palmate foliage but the majority are known as 'angel-wing begonias' because of the unusual shape of their leaves. Foliage colour varies from fresh green through to bronze or blackish-green in some cultivars. Many varieties are beautifully freckled with silver or white spots or splashes, or veined in a contrasting colour. Others have a dramatic contrasting colour on the underside of their foliage.
Blooming can begin in November and extend until August in mild climates, and is at its peak in late summer and early autumn. The thick pendulous trusses of long-lasting waxy flowers make the stems arch over attractively. Flowers come in many shades of pink, as well as red, white and orange. Tall favourites include Begonia 'Irene Nuss' with lustrous bronze leaves and salmon pink flowers (ht 1.5 m); Begonia 'Sophie Cecile' (ht to 1.5 m) with silver splashed, deeply cut foliage, which is mahogany beneath, and rose-pink flowers; and Begonia 'President Carnot' (ht to 1.5 m), which has green leaves with a burgundy underside and brilliant red blooms. 'Orange Sherbet' has vibrant orange flowers. One of the most commonly seen cane begonias, Begonia undulata, can grow to 3 or even 4 m if unpruned (otherwise its height is around 2 m) and it has fresh green leaves and crisp white flowers. It can make an effective, informal hedge. On a smaller scale, Begonia 'Pink Cascade' (ht 1 m) has soft pink flowers; Begonia 'White Cascade' (ht 1 m) has dark green foliage with silvery spots and clean white flowers; and Begonia albo-picta (ht 1-1.5 m) has white to pale pink blooms and silver spotted leaves. There are also various hybrids which grow to less than 50cm in a range of colours.
Like many Begonia, these plants thrive in a part-shaded position with a couple of hours of morning sun, and are wonderful plants for dry spots, as they dislike being over-watered. Some of the tougher forms can also survive in hot, sunny spots: flower colour can be darker when these are grown in sun. Their upright form makes them ideal for narrow spaces such as at the side of the house. Cane-stemmed Begonia are excellent subjects for pots, especially in cooler areas with frosty winters, which these semi-tropical plants - originally from Brazil - do not like. The pots don't have to be huge and can be moved into a sheltered position during the winter months. Add perlite to the potting mix used for the pots, to improve drainage or use African violet potting mix. Don't overwater the pots. Larger cane-stemmed plants need a heavy pot so that the plant doesn't topple over. Alternatively, if the plants are grown in the ground beneath trees, this can provide shelter from light frosts. The stems are quite brittle, so tall specimens need protection from strong winds. Make sure that pots are only watered when the soil surface dries out. Small, compact cultivars can be grown in hanging baskets, and their stems will arch over the sides of the basket.
Companion plants for cane-stemmed begonias can include shade-lovers such as Hydrangea, Plectranthus, Justicia and Impatiens, which flower at the same time as the begonias. Cane-stemmed Begonia with silver spotted leaves look very effective growing with shade-tolerant silver foliage plants such as Plectranthus argentatus or Helichrysum petiolare. Accompanying strap-leaved or bold architectural foliage - such as that of Clivia, Philodendron or taro (Alocasia) - can provide contrast of leaf form whilst emphasising the semi-tropical nature of the begonias. They can also be underplanted with any of their attractive cousins, the low-growing rhizomatous Begonia, which have stunning patterned and coloured foliage and form an attractive carpet in dry shady areas.
Cut flowers and foliage of the cane Begonia are excellent for use in vases. To prune, old brown canes can be removed at ground level in late winter (at the end of August - a little later in very cold suburbs) and the rest of the canes trimmed at the same time by one-third to a half to make the plant bushier. Newly emerging canes - which resemble bamboo shoots! - should be left unpruned. The plants can be fertilised with a general-purpose or slow-release food and given a blanket of mulch after they are pruned. Occasionally liquid feeds during the growing season are beneficial. Plants in pots can be given a slow-release fertiliser. They rarely seem to be bothered by pests or diseases, though may occasionally get some powdery mildew on their leaves. Use an organic fungicide to control this problem. Eventually, old plants may lose their vigour (after about ten years or so) and then should be replaced by a new specimen. To propagate the plants, take tip cuttings with two nodes in the warmer months. They strike easily from cuttings: the best months to do this are March, April and November.