A visit to the Botanic Gardens last week reminded me of how useful the genus Begonia is in our Sydney climate. At the moment, the rhizomatous Begonia there are smothered in dainty clouds of flowers, creating a pretty, mid-spring picture. One of the best attributes of these plants is that they will grow in dry, inhospitable shade. We all have such spots in our gardens, usually under trees or shrubs where few plants will thrive. By massing groups of rhizomatous Begonia, we can make an effective evergreen carpet in these adverse conditions.
They are tough, evergreen groundcover plants with thick creeping rhizomes that have shallow roots and low water needs. They have an incredible diversity of leaf forms, which vary in shape, size, surface texture, colour and patterning. These range from rounded forms which look like lily pads, to lop-sided hearts, stars and slim-fingered hands. Others have leaves with their centres coiled into three-dimensional spirals. Some have leaves with a highly lacquered sheen while others have velvet, hairy or pimpled surfaces. Leaf edges may be smooth, ruffled, twisted or saw-toothed. Leaf colours vary from bright to dark green, brown, gold, lime, silver, pewter, purplish brown to near black; with or without contrasting coloured veins, edges, splashes, streaks or coloured undersides.
A planting of a few different types of these begonias will soon knit together to form a rich patchwork quilt in a dry shady situation. Plain-leaved ones can be alternated with patterned forms, and colour can be played with: juxtaposing silvery leaves with darker foliage for example, to create a dramatic effect. As shown in the Botanic Gardens Begonia beds, they also contrast well with upright, strap-leaved plants that tolerate dry shade, such as Liriope, renga-renga lilies (Arthropodium cirratum) and bromeliads; as well as with ferns.
The flowers are usually pink or white, and hover above the leaves for several weeks. They can act as a substitute in warmer areas for the airy spring woodland blooms of Heuchera, Tiarella and Tellima that do not thrive so well out of cooler climates, and they can provide an attractive display under spring-flowering shrubs.
There are many cultivars of rhizomatous begonias, and collecting them can easily become an obsession. Some reliable favourites include B. bowerae (ht 15cm, dark 'eyelash' edging on bright green foliage; pale pink flowers); 'Cleopatra' (ht 30cm, lime green, star-shaped leaf with brown markings; pale pink flowers); 'Erythrophylla' (ht 30cm, the so-called 'beefsteak begonia', with leathery, olive green leaves, red underneath; pink flowers); 'Kara' (ht 60cm, large, crinkled, dark green and chocolate foliage; pink flowers); and 'Silver Jewel' (ht 15cm, pebbled, green leaves marked with silver; white flowers). Some of the very fancy, unusual cultivars can be difficult to grow in garden settings, and are better suited to life in a pot.
In fact, where space doesn't permit the plants to be grown in the ground, any of the rhizomatous forms can live very happily in shallow pots or hanging baskets on a shady veranda. They should be kept on the dry side, as over-watering them can be fatal, whether they are in a pot or garden bed.
The plants are sometimes hard to find in general nurseries; however, several specialist begonia nurseries do exist, and the Friends of the Botanic Gardens Nursery in Sydney sells them. The NSW Begonia Society will be holding a display and sale of all sorts of Begonia on Saturday 7 November 2009, 10 am - 3 pm at 226 Annangrove Road, Annangrove NSW.
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