When you consider that tuberous begonias can flower continuously from June until frost, have blooms that last more than a week, are easy to grow, and come in just about every colour, it’s a wonder more gardeners don’t grow them.
If this is your year to try growing tuberous begonias, now is the time to get them started.
The neat thing about any flower bulb is that it’s a complete flowering kit with food and flower in a durable package (bulb). This food can be delicious, and if you have any bulbs like potatoes, onions, garlic or ginger root, you know what I mean. The begonias we’re discussing grow from concave-shaped tubers. They like a barely moist soil and bright, dappled shade.
Since tuberous begonias flower non-stop, the sooner you get them going, the sooner (and longer) they’ll start blooming. Use shallow trays or pots, and plant the tubers concave side up in well-draining potting soil. Cover the bulbs with no more than one-half inch (1 cm) of soil.
Begonia tubers can take awhile to wake up from their winter dormancy, so be patient (an essential virtue every gardener needs). Once they’ve produced leaves, you can transfer them to their final containers.
The minimum pot size for a single tuber is six inches (15 cm) in diameter or three in a 12-inch (30-cm) pot. Some of you may want to plant them directly in the garden, which is fine provided you remember to lift them and bring them indoors before a hard frost. It’s simpler to pot them in terra-cotta pots and plunge the pots in your flower beds, lifting them — pot and all — before winter. Tubers can last for many years if you overwinter them indoors.
Tuberous begonias hate heat, so place them in bright, dappled shade, in morning sun or anywhere where they won’t get baked by midday sun. Their fleshy stems can be fragile in the wind.
Soil for potted bulbs
Why buy potting soil when you can make your own? I mix equal parts peat moss (or coir), well-rotted manure and coarse sand (the kind used to make cement). This provides the food, moisture retention and drainage summer-flowering bulbs like. You’ll know if your bulb is happy if it’s larger at the end of the season than it was at the start.