Lynne Cullen
On Tuesday March 4th the Daylesford and District horticultural Society welcomed Pete Harris from Whitehouse Nursery in Ashbourne, a boutique and rare plant nursery, as their guest speaker. Pete has expert knowledge of many plant species but his focus for the evening was on tuberous begonias renowned for their superb flowers that look like gerberas, roses and peonies. Many examples are can currently on display in the Alf Headland Conservatory near Wombat Hill House in the Botanic Gardens.
Tuberous Begonias originated in The Andes, particularly Bolivia, in a harsh environment clinging to rocky outcrops and crevices. They tolerate minus 12 degrees and so are well suited to local winter conditions. Other begonia species such as Rex and Cane would not survive these conditions.
Tuberous begonias thrive in cool shady environments and tolerate only morning sun.
The tubers, available for purchase during their dormant period in winter, should be placed first in 3-inch pots first in a good quality potting mix with slow release fertilizer. They do not like wet feet so should not be overwatered. They will die if they become root bound so when the roots hit the side of a pot, the plant needs to be potted up. The usual sequence is upgrading from 3 inch to 6 inch to 8 inch to 10 inch pots as a natural progression. They can be staked in large pots with hardwood stakes placed near the tuber. Twine tied in 2 figures of eight every 15 cm can be used to hold the plant up straight particularly when the flowers develop as they are very heavy. Note that they can grow up to 1 metre in height.
Since they are light sensitive, in Australia they begin to come out of winter dormancy around September. In Summer the plant is groomed by disbudding, removing dead flowers and leaves along the stem. Do not let them fall. The plants are watered and fertilized in summer with about 20 Osmocote pellets per plant. Tuberous begonias have male and female flowers. The male flower is the grand flower with many petals whilst the female is much smaller with only 4 petals and ovaries beneath the petals. The female flowers can be removed for display. These distinctions are evident in the Wombat Hill Botanic Gardens display, where you can see the luxurious male blooms contrasted with the much smaller four petal female ones.
Summer and autumn are the main flowering seasons. They should be fertilised every 3-4 months although not past the end of summer as too much fertiliser later on will prevent the plant falling asleep.
By late April, watering only once a week is required and by the second week of May watering stops altogether. The growing tips can be pinched out of the plant to hasten dormancy. By the end of autumn, leaves will yellow and flowers droop. The plant will then begin its own path of attrition as each part falls off and all nutrients return to the tuber. The bulb shrinks as the plant grows but then expands during dormancy as all nutrients return to the bulb.
Proper storage of begonia tubers is crucial for ensuring healthy regrowth in the following season. Once the plant has completely died back, soil should be gently teased away from the tuber rather than forcefully removed. Shoots should not be rubbed off. Some growers store tubers wrapped in newspaper, while others, like Whitehouse Nursery, use specialized storage sheds.
Proper storage of begonia tubers is crucial for ensuring healthy regrowth in the following season. Once the plant has completely died back, soil should be gently teased away from the tuber rather than forcefully removed. Shoots should not be rubbed off. Some growers store tubers wrapped in newspaper, while others, like Whitehouse Nursery, use specialized storage sheds.
Begonias can be propagated through seed or cuttings. For seed propagation, pollination must occur at temperatures above 21°C. Male and female flowers must be crossed, and successful pollination results in a seed pod forming within six to eight weeks. Seeds should be sown in peat moss under artificial light in June or naturally in October-November.
Cuttings—whether from leaves or stems—can be taken until late January. Buds from older stems work best, and the cuttings should be placed in compacted peat moss. A wooden skewer can be used to stabilize leaf cuttings. Some gardeners use honey diluted in lukewarm water as a growth stimulant instead of synthetic rooting hormones. Covering the cuttings with plastic bottles can create a mini greenhouse, aiding moisture retention and root development.
Pete Harris’ presentation was an extremely useful and informative session and the Hortis were very grateful to Pete for his time. Pete also donated two superb begonias for the Horti raffle on the night.
Our Daylesford Horticultural Society meeting is on Monday March 31 (not the usual Tuesday evening) featuring noted fungus expert and nature photographer, Alison Pouliot. The event will take place at the Pavilion at Victoria Park rather than the regular venue at 113 Main Road, Hepburn. The event is open to everyone but please email the Hortis at horti@outlook.com.au to indicate that you intend to attend.
Lynne Cullen is a local resident and a Committee member of the Daylesford Horticultural Society.
