Growing Tuberous Begonias

By Therese Ciesinski, GardenSMART

I adore the double-flowered tuberous begonias, with their blowsy petals and lush foliage, but prices for a blooming plant in a hanging basket are astronomical. Late last winter I saw tubers for sale at my garden center for a fraction of the price and thought, what do I have to lose?

They took a bit of coddling to get started, and were slow to sprout, at times leaving me sure that I’d killed them. But eventually they went from brown, dry cow patties to being covered in tiny pink and white growth buds. Planting them and waiting for what seemed like forever for the stems to emerge was exciting and a great winter project.

One of my begonias at the beginning of August. Photograph by Therese Ciesinski.

Double flowered tuberous begonias are tender plants in almost all of the U.S., other than in frost free areas in U.S.D.A. Plant Hardiness Zones 9 to 10. They are native to tropical South America and therefore extremely sensitive to cold. Shade lovers, these begonias come in colors that range from white through yellow and orange to pink, coral, and red. There are also varieties with petals in contrasting colors. Their flowers resemble those of roses or camellias. A healthy plant in full bloom is a showstopper.

All the tubers sprouted. I planted them up in hanging baskets and brought them outside once night temperatures stayed consistently above freezing. Even with the slow release fertilizer I added at planting and bi-weekly watering with fish emulsion, it took a while for them to finally flower. But when they did, oh, were they worth waiting for!

The same begonia one month later. Photograph by Therese Ciesinski.

Each satiny white petal was tinged with pink. The stamens were a bright, egg-yolk yellow. Some flowers were indeed double, with ruffled petals. Others were singles but no less pretty.

As beautiful as the blooms were – and I’d grow them again for that alone – it was the fragrance that made all the coddling worthwhile. It was lemony, strong enough that you could smell it as you passed, but not cloying or perfume-y. I hung one basket outside the front door so we could catch a whiff as we came and went.

Tuberous begonias are shade plants that nevertheless grow best with indirect or dappled light. They need protection from wind. Their stems and leaves are brittle and break easily. Other than periodically turning the baskets so that all sides of the plant were exposed to light, I handled mine as little as possible.

Begonias flower in colors ranging from white, through yellow and orange, and pink to red.

These plants require well-drained soil, however they are not drought tolerant. Never allow the soil to completely dry out. They are heavy feeders, so for consistent flowering, keep to a fertilization schedule.

The plants didn’t start blooming until July, but once they took off, they bloomed their heads off. We had an unusually warm fall, with no frosts until November, and they were protected hanging under the eaves, so amazingly they flowered until late October, when I finally brought them in.

Begonias have brittle stems that break easily.

I let the soil in the baskets dry out, as directed, and have removed all the stems and foliage. The tubers are supposedly dormant. Now comes the challenging part: can I successfully overwinter them and get them to bloom again next summer? Stay tuned.

If you’d like to try growing your own begonia tubers, check your local garden center or big box store. The largest variety of colors and bloom forms will be found online, however, at mail order companies that specialize in flower bulbs.

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