Growing Begonias

The City of Ballarat horticultural team tend to our Begonias for 10 months of the year. Here is a little bit about what they do to keep our famous Begonias at their finest for the Ballarat Begonia Festival.
Once cleaned, tubers are stored over winter in a cool, dry and dark environment covered with vermiculite to help keep them dry. They are not watered whilst dormant.
They are potted just as buds form, usually around September to October, into quality free draining potting mix with slow-release fertiliser incorporated.
The Begonias then only receive liquid feed with seaweed concentrate at the standard dilution if required.
Pots are hand-watered, at the soil level to assess each plant’s watering requirements and to reduce fungal diseases that can occur with wet foliage.
It is a misconception that you require a heated glasshouse to grow Tuberous Begonias in our area. Begonias are cool climate plants that require good air movement.
The City of Ballarat grows Begonias in our unheated glasshouses, primarily due to the fragile nature of the stems and to protect the flowers.
The original Begonia’s from which most of the Tuberous hybrida have origins, grow in tropical zones but at altitudes where it is a cooler climate.
Flower size can be reduced by the hot weather, particularly if a series of hot days occurs around November.
Tuberous Begonias grown in our conditions would naturally come into flower in January, however we regularly remove flowers and buds up until four weeks prior to the Festival, to produce the best blooms for the March display.
After this period, all single female flowers are removed from the plants to encourage the growth of larger, showier male (double) flowers.
Each plant stem is staked, and individual flowers are supported with wires to help support the weight of the blooms. Labour intensive but worth it!
It is important not to overwater tuberous Begonias as the tubers are prone to rot.
The surface of pots is best left to just dry out between watering and potting mix must be free draining.
Hand watering at the pot level also helps to assess each individual plant’s needs and also reduces the spread of fungal diseases such as powdery mildew.
The plants do naturally go dormant (a bit like a daffodil), usually around early May in Ballarat. This is characterised by the yellowing of the leaves.
At this point, watering is reduced and allows Begonias to go dormant naturally. The above-ground part of the plant will fall off.
Once dormant each tuber is cleaned, checked for any pests, and diseases, and then placed in vermiculite to keep them totally dry. They are then stored for winter in a small dark room like a large walk-in pantry.

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