The begonias with the large colorful flowers are the Tuberous begonias. Easily recognised from cane begonias by those colourful flowers, often portrayed as difficult to grow, but not so tricky given a little care, the right watering regime and the right climate.
These plants are originally from the rainforests of South America although they have been extensively hybridised since their discovery and now produce the spectacular flowers we have grown to admire so much.
The Red and White frilled tuberous begonia (pictured right) is just one example of the many hybrids available for sale from a number of specialist nurseries in Australia today.
How to Grow Tuberous begonias
It is essential to remember tha the Tuberous Begonia (, or Begonia x tuber hybrida) are a ‘cool climate’ plant, anywhere north of Sydney can be problematical. They need cool night temperatures which means they prefer to be grown outside, a shade house or a patio is generally ideal.
Todays hybrids do not like high temperatures or humid conditions, so in Australia they tend to do well in southern states especially the cooler areas, however these conditions can be replicated using areas of part shade or dappled shade.
The fertiliser regime we use is a slow release fertiliser in spring, and regular watering with a seaweed based fertilizer.
These plants flower in summer to early autumn when the days are long and they get plenty of light. A well drained humus rich soil is best, tubers do not like to be wet as they tend to rot especially in winter when they are dormant. Many growers overwinter tuberous begonias in a tray of potting mix in a cool position.
If you allow the potting mix to dry a fair bit, but not completely between watering you will avoid many of the fungal problems.
For those who know their geography and climate zones consider that Ballarat in Victoria is home to the Begonia Festival in March each year and the spectacular main display is in the Robert Clark conservatory.
These begonias need a dry winter and this means the containers should be lifted off the ground and placed out of the rain. For the growing season they do like to dry out a little between watering.
The best potting mix is one free of water retention crystals, and one with some additional perlite added in for good drainage. Remember that tuberous begonias like to be a little ‘crowded’ in the pot, so choose a container that is not to large.
Fertilizer is applied during the growing season and we like to use a low nitrogen slow release type along with a watering of liquid seaweed fertilizer.
Division and propagation
You can divide tubers, however this can be tricky as when cut diseases can easily get in, so wait until spring when they are in active growth, this helps with healing and prevents rot.
Cuttings can also be taken from the multiple shoots that appear on Tuberous begonias, you can usually work them away from the tuber with a little gentle manoeuvring, and look for the little bud just below the surface, they need this to grow. They strike fairly easily if you look for shoots that are around 4 inches tall (10cm) any taller and they tend to struggle a little.