Growing Tuberous Begonias

If you’re looking for something that really puts on a show, you can’t beat a California Tuberous Begonia. Plant a bunch of this variety, and come July/August, your yard will be alive with iridescent whites, pinks, reds, oranges, and yellows. If you’re new to gardening, just start with a dozen or so. They take a little extra work, but once you learn a few tricks, begonias make for an enjoyable hobby.

First, you want to buy your begonia tubers this month, the sooner the better. When purchasing, keep your standards high. Ideally, the tubers should have the consistency and firmness of a potato. If they’re a bit dirty, that’s okay. But pass on any that look at all shriveled. By the same token, watch for soft, mushy tissue and any signs of fungus or mildew. If you can, buy from the bulk bins. If you don't have that option, just make sure you steer clear of any tuber you can't touch first or that are packaged in a way that doesn't allow for airflow.

There are 3 types of Begonias

• California Hybrid Tubers These are very large and excellent performers… quite possibly the cream of the crop.
• Belgium Begonias Normally smaller and less expensive than California Hybrids, they still perform great.
• Non-Stop Begonias (grown from seed) Though they form into smaller tubers, they’re normally only available in plant form in 4-6" pots. Lots of people use them in hanging baskets, but because their habit is upright you won’t get that geranium-like trail and flow.

As for planting…

Here's a method that resulted from a few years of trial and error to develop by one successful tuberous begonia gardener.

• Using top quality soil, set the tubers 1-2" apart (cup end up) in a starter flat, keeping them from touching. Plant the tuber shallow enough so that the top is showing slightly.
• When they reach 4-5" tall in a few weeks, lift out the tuber (being careful not to damage the roots).
• Re-plant the tuber 1" deep in a 7" or greater diameter pot, using top quality potting soil. Use a pot with a hole in the bottom wide enough for a stake to go through. Pick a shady spot, and drive a 20" stake through the pot and into the ground, deep enough that the stake can brace a begonia stalk. As the stalk grows, it will become increasingly herbaceous and heavy. Often, the plant will want to fall over from the weight of the stem. Use a twist tie or wire tie to bind the stalk to the stake as it grows, making sure it isn’t so tight as to cut off circulation.

Fertilizing & Watering

Use a 20-20-20 fertilizer every 7-10 days until the plant grows to about 6" high. Then cut back to fertilizing once a month. Try Alaska Fish Fertilizer, too -- it seems to work great with begonias. Water carefully, about once a week throughout summer. Don’t over do it, yet don’t let the planter dry out either.

Additional Care

• Pick off the dead leaves and blooms.
• Spray with a "Funginex" if plants get mildew on them.
• Remember, begonias are shade plants. Though they can handle a little mid-day sun, you need to watch their direct solar exposure.
• In the fall, When the plants have died back to the ground, dig up the tubers, allowing some soil to cling to them. Place the tubers in a sheltered frost-free spot for a few weeks, until they are so dry that their stems and the soil around them break away easily. Store the tubers over the winter in dry vermiculite, perlite or peat moss at 40° to 50°.

Go ahead, Give a few begonias a try this year and see what happens.

While much of the information in these tips is applicable in several gardening zones/climates, some of the plants and timing suggested are best suited to the Northwest, generally in the mild/wet growing regions found along the I-5 corridor. You should make appropriate adjustments or consult local gardening experts in regions whose climates differ from this area of the Northwest.