Well-known Tauranga plantsman John Burton loves his tuberous begonias and has been growing them for many years for a bounteous summer display. In this area tubers can be planted in a good, open-draining potting mix in September and October.
Up to three plants can go into one large basket. The baskets need to be shaded through the middle of the day and sheltered from strong winds. In the past John has put several baskets to hang from a small tree and also fixed them to the walls of a house.
John, who has been involved with plants for nigh on 65 years, advises keeping the baskets moist and feeding with a liquid fertiliser every two weeks during flowering.
“Removing small, single [female] blooms off the flowering stems means larger flowers that will last longer,” he says, adding that mildew is about the only problem that affects begonias.
When flowering has finished, the leaves will start to yellow. Gradually reduce watering before drying off the basket.
Remove the tubers and store in a paper bag in a dry, airy place. Before storing, check the tubers for rot and dust with flowers of sulphur to prevent decay over winter. Although tubers will last for several years, they may begin to lose vigour as they age so a good idea is to take cuttings from the new shoots each year. Read more about propagation here.
“They are very rewarding plants for the small amount of effort required to grow them,” John says. “They flower for three to four months over the summer.” He recommends annual lobelia, impatiens, alyssum and fuchsias as plants that combine well with cascade begonias. Read more about growing begonias here (an Auckland-based website).
Read more about begonias at this website, but note that although it has a New Zealand domain name, the information comes from all over the world so you may have to adjust the months to match where you live. For instance, the item on growing begonias from seed says to plant from January to mid-March – at the bottom of the article it can be inferred that the author is in Britain. There is a Begonia Circle in Auckland.