Growing Begonias in Australia

These drought-tolerant perennials come in a variety of forms. DEBBIE McDONALD outlines the options, with tips from an expert who has grown begonias for 30 years. As exotic, succulent perennials hailing from tropical and subtropical regions, begonias are ideal plants for our gardens. During warmer months, you'll often see bedding, or semperflorens, begonias for sale or mass-planted in public gardens. They grow 15-30cm tall, with red, pink or white flowers and bronze to apple-green leaves.

Although these are the most common begonias around, there are many other beautiful options. Out of the nine basic groupings of begonias, the best choices for our gardens are rex, rhizomatous, shrub-like and cane-like. Begonia expert Peter Sharp also recommends a group called Non-Stops. These tuberous bedders have been specially bred for garden growing, and thrive in shaded areas. For gardeners wanting a groundcover, trailing or scandent species can be grown to trail or climb.

Rex begonias are grown for their foliage, which is ornamented with swirls, spots and stripes in black, silver, green, red and purple, with a range of metallic sheens and interesting shapes. They grow 30-60cm tall and about 30cm wide.
As frost-tender subtropical plants, rex begonias are perfect for indoors. After many years of hybridising and with just one common ancestor, B. rex from Assam (a state in India), they are now heavily inbred and have lost much of the vigour essential for garden growing. Place them inside in bright light but out of direct sun.

At just 20cm high, rhizomatous begonias look great as a groundcover. Leaf colours range from black to vivid green, with pink, red, orange or white flowers. They have a thick rhizome, which stores food and water, so are drought tolerant.

Lush, bushy begonias are in the 'shrub-like' group. While they can be grown in the flower bed, try them among ferns, cordylines, crotons and bromeliads as a contrast in height and shape. With fern-like leaves, B. foliosa is one of the best.

Cane-like begonias are just that. They have upright arching canes 60cm to 2m tall, with patterned foliage and pendulous flowers from spring until late winter. The flowers hold well, giving long-lasting colour in the garden.

Growing and Propagating

Gardeners are often drawn to begonias for their shade tolerance, and it's true that many varieties do well in shaded gardens. Indeed, some, such as Begonia listada, are deep shade lovers. But, as Peter notes, the branding of begonias as shade plants is not entirely accurate. "My experience growing begonias as garden plants has shown that what we thought of as shade lovers are in fact sun lovers, which grow so much better when exposed to it in various amounts," he says.

So while some plants prefer full shade, others like dappled shade or morning sun. Others, such as bedding begonias, are happy in full sun. Check the light requirements of your plants by looking at the undersides of the leaves. If they're dark, the plant likes shade; if light, it needs a bit more sun.

Begonias are readily available at nurseries, but are also easy to propagate. With cane-like begonias, take 10-15cm tip-cuttings in autumn, trim off the lower side leaves, and insert into propagating mix. Water when the mix is dry.

For rhizomatous begonias, use a section of healthy rhizome or a leaf cutting. Slice large leaves into wedges, each with a main vein. Insert the stem or wedge with the vein pointing down into propagating mix. Firm in and water.

Where to See Begonias
Royal Botanic Garden, Sydney, has an impressive collection of garden-grown begonias adjacent to the Macquarie Wall. Ballarat Botanical Gardens shows off its famous tuberous begonia collection at its annual begonia festival, March 10-12.

Expert Tips

Peter Sharp is begonia adviser at the Royal Botanic Garden, Sydney. Here are his tips for growing begonias.

  • Growing conditions Begonias like an acidic soil (pH 5.5-6.5). Humidity around 60 per cent is ideal, and good drainage is essential. Potting mix for indoor use must be of good quality, and not produce sludge in the pot bottom.
  • Fertilising Add controlled-release fertiliser to the planting hole, and apply a good general-purpose liquid fertiliser at 3-4 week intervals (or fortnightly for pots, due to leaching).
  • Watering Water pot-grown begonias when the soil surface dries out - test with fingertip to 2cm depth. Ensure when you water that the pot is saturated. Avoid watering foliage. If it's an indoor plant, do it outside and leave in a well-lit spot for half an hour or more to drain. In the garden, water deeply as required, which is not as often as people may think. Begonias are succulent or semi-succulent plants so accept quite dry conditions. Overhead watering won't harm them.
  • Pruning All begonias benefit from regular pruning. Prune the cane-likes annually, from mid to late winter. Up to two thirds may be safely removed to achieve the shape and size you want.

The shrub-likes need tip-pruning in the early stages to encourage lateral growth, and overall pruning as adults to achieve the desired shape and habit. This may be done at any time.

Semperflorens (bedding begonias) need to be tip-pruned frequently during the early growth stages to encourage a more compact and better-flowering plant. Prune heavily if they are leggy.

Once rhizomes have finished flowering, pinch out the growing tip to encourage the development of laterals and a fuller plant. Old leaves should be removed at the end of winter.

How to Propagate a Begonia
Peter demonstrates how simple it is to make new plants from tip cuttings.

  1. Cut the stem at an angle. Trim off the side leaves close to the stem, and cut the top leaf in a wedge.
  2. Near the side of the pot, make a hole with a pencil or stick. Four cuttings can fit in each pot.
  3. Insert the cutting into the hole and firm it in with a finger. The side leaves should be above the soil.
  4. Always name your cuttings. Use an indelible pen. Water gently when mix begins to dry out.

Gardening Australia Magazine, March 2012


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