How to grow begonias

01/07/2024

Fast facts about growing begonias

How to grow begonias in pots

Begonias are just as at home in a pot as they are in the garden. To grow a begonia in a pot, you need to allow for growth, so ensure you choose a pot that is twice the width and depth of the plant. Remove the begonia from its container and gently tease the roots apart, position it in the pot and backfill around it.

How to propagate begonias

Love begonias? Make more! You can easily propagate a begonia from cuttings. Slice a leaf into wedges, dip it in a cutting powder and place it on a tray of moist seed-raising mix. Pop the tray in a spot that receives lots of natural light and keep it moist. The entire process should take 6-8 weeks. Alternatively, you can pop a stem cutting in water to form roots, which you can then plant when they reach 4-5cm long.

Begonia varieties

Before you get planting, you'll have to choose the right begonia for your garden. First there's the showy tuberous begonias or elatior hybrids that rival roses for floral flourish. Then there’s the rex with mosaics of intricately patterned and coloured leaves.

Cane stemmed begonias

Tall growing, up to 1-2m, these varieties bloom from mid-summer to mid-autumn with fleshy flowers like little chandeliers, in shades of pink, red, orange and white. One of the most popular is B. coccinea, which has pendulous heart-shaped leaves with red undersides and margins.

You can use the tall-growing cane begonia (B. coccinea ‘Alba’) as a screen or even a hedge in your garden. They need stakes and training, as some stems decide to grow horizontally. If so, use long ties and tighten a little each week so the training is gentle. They’re stately plants, great for filling areas of the garden that need a vertical element. Or try them as specimen plants in large pots, on a verandah or in a courtyard.

Shrub begonias

These are robust plants; they come in many sizes, colours and leaf shapes, and bear flowers for many months. They can handle being a little on the dry side and prefer semi-shade.

A few standouts in the group are Begonia venosa, with rounded silver-grey velvety leaves, B. metallica, with purple-veined leaves, and the majestic B. luxurians, with leaves that look almost like a palm frond – green on the topside and red underneath.

Unlike the cane-stemmed varieties, shrub begonias will branch, so prune in late winter to promote new growth.

Tuberous begonias

Renowned for amazing glasshouse displays, begonia tuberhybrida, or tuberous begonias, have gorgeous double flowers that appear in late spring and summer. They make delightful pot or window box displays.

Best in filtered shade, they like a little morning sun in cooler climates. Allow the potting mix to dry out between waterings and store the pots somewhere dry over winter.

Elatior begonias

Eliator begonias make exceptional indoor plants or in hanging baskets, elatior begonias (Begonia x hiemalis) are short-lived but flower prolifically and come in fabulous colours, from hot reds and oranges to softer sherbet-like pinks, lemons and apricots.

A group of two or three pots of these little beauties will brighten any room. In terms of growing, they like rich, well-drained soil and detest soggy feet. Grow them in African violet potting mix and keep it evenly moist. Cut back spent flower stems to 5–10cm long, to revitalise the plant and encourage new growth.

Elatiors love being indoors but prefer to have a moist environment, so keep them away from air conditioners. They’ll add a soft touch to the hard, gleaming surfaces of a bathroom! Just be sure they have access to bright but indirect light.

Rex begonias

Also known as king begonias, Rex begonias have the name for good reason. While their flowers are insignificant, their foliage is like a royal robe with purple, pink, maroon, pewter, silver and shades of green splashed on the foliage in dazzling combos.

They grow well in pots and hanging baskets in bright filtered light. They need high humidity but hate soggy roots, so water only when dry.

Begonia semperflorens

Also known as bedding or wax begonias, these are the hardiest of the bunch, thriving in full sun in cooler regions or in shade where it’s warmer.

Each plant produces a super abundance of flowers during summer of single or double, open-faced flowers in exquisite white or many shades of delicious pinks and reds.

They poke out of circles of fat, round, waxy leaves that can be coloured dramatic black or deep purple, shiny bronze, glistening greys or in many luminous shades of green.

Mass plant them in a garden bed or in a pot you can bring indoors when it gets cold. Prune spent flowers to encourage more of them as the season progresses.

Diseases to look out for

Begonias are fairly robust but you will need to look out for and treat these problems to keep your plants in tip-top shape. The best place to start is upon purchase – inspect the plant carefully for any signs of disease or insect damage. If it looks weak and leggy, or has any holes, spots or discolouration on the leaves or stems don’t buy it, as it will not thrive.

Another fungal disease that affects begonias is powdery mildew, which leaves a grey/white coating on the undersides of the leaves, eventually causing them to wither and die.

To rid your begonia of this, water the soil around the plant in the morning and avoid splashing the leaves. You should also remove any affected leaves with sterilised sharp scissors or secateurs. There are commercially available sprays that are useful in treating this disease.

Finally, your begonias may suffer from dark brown, crisp-looking marks on leaf edges, which are usually caused by low humidity.

To fix the problem, place your potted begonia in a tray with pebbles and water, making sure the pot base doesn’t sit in the water to prevent root rot. Alternatively, you might notice a pale brown or yellow scorch mark on all, or part, of the leaf – this is essentially sunburn.

Cut off the leaf and discard and move pots into a more sheltered spot, or give garden plants a new position that doesn’t get direct midday sun.

Pests that can affect begonias

Insects such as slugs, snails and green lopper caterpillars like to have a meal on their leaves.

Treat the slugs and snails with bait and pick off the caterpillars. White fly, mites and scale can also be a problem, but you can treat them with an appropriate chemical spray, checking the label for application rates.