Napa County
Newspaper Articles  Begonias

By Denise Levine, U. C. Master Gardener

Tuberous Begonias
Tuberous Begonias
My grandmother grew begonias. Her garden was a screened patio that defied the hot Sonoma Valley sun, and in the summer it overflowed with pots and baskets of tuberous begonias.

On my overnight visits, a garden chaise would be rolled into that porch room and fitted with sheets and pillows for me. I would waken to morning sun shining through hanging, pendulous blooms of translucent color. Deep salmon pinks and shocking coral blossoms hung heavily over the sides of the wooden boxes that housed them, and when I got up close to study these foreign-looking plants, I could see the cell walls of the luxurious, succulent petals and the tiny hairs on the textured, coarse reddish-green leaves.

This year my childhood memories have propelled me to the nursery in time to buy begonia tubers to recreate that haven of my youth. Luckily, according to Maureen Jensen at Van Winden Pueblo Garden Center in Napa, growing tuberous begonias is pretty simple, and recreating those voluptuous overflowing pots is easily within reach.

Although tuberous begonias can be grown from seed, normally they are grown from tubers planted in spring. Buy tuberous begonias now to plant this month and next and you can enjoy summer blooms that can last through fall.

Look for the largest, most solid-feeling and unblemished tubers you can find. Try to avoid tubers that feel spongy or have soft spots.

Jensen told me that over the years she has been most successful starting the awkward-looking tubers first in small individual pots inside, where it is warm.

Using any good potting soil, fill a four-inch pot. The begonia tubers can sometimes have tiny buds beginning to show which is helpful in telling the top from the bottom. If no clues are evident, the rounded side goes down, with the cup-like indentation facing skyward.

If the top is too concave and looks like it could collect water (which would encourage rot), tip the tuber slightly so water will run off, then press into the soil until it is firmly set. The bottom of the tuber should be under the soil line, but the top of the tuber should be exposed. Water well and keep in a warm, sheltered place where temperatures don’t dip below 60ºF. You won’t need to water again until leaves begin to emerge and it is evident that dormancy is broken. Then your tuberous begonia is on its way to summer glory. Water regularly through the growing season, feed them bulb food according to the package directions, and keep in a sheltered spot, out of the hot sun.

When transplanting them to their summer homes, choose pots suitable for the type you are growing. Hanging baskets show trailing varieties (such as Begonia pendula) to their best advantage, while groups of deck pots can display upright varieties (such as B. multiflora or B.hybridia). You can grow single plants in six-inch pots, or space plants about four inches apart in hanging baskets or larger pots.

With these simple instructions, I went out to choose my flowers. Tubers for soft white and rosy pink hanging begonias tempted me first. Each tuber fit nicely in the palm of my hand and felt solid and heavy for its size. There were definitely two sides, one slightly rounded and relatively smooth while the other was rougher, with a few more bumps and a slight indentation towards the center.

Next I chose some upright-growing “rose form” begonia tubers. They were slightly flatter with more noticeable root hairs, but the general shape of the tubers was the same.

According to Jensen (who remembers her own grandmother’s collection of potted begonias lining the porch), tuberous begonias get bigger and more beautiful every year with proper care. To assure their longevity, watch your begonias when fall weather turns cold and they begin to die back. If they are in pots, you can simply put them in a garage or potting shed until spring weather prompts their first foliage buds. Then put them back in a warm, sheltered spot and begin watering and feeding. If you have planted your tuberous begonias in beds, dig them out, dust them off and put them in a cool spot until spring. Then follow the directions all over again.

Upvalley residents can drop into Whiting Nursery in St. Helena for begonia tubers and expert advice and start planting now for gorgeous flowers this summer.

© 2021 - Regents of the University of California
Division of Agriculture and Natural Resources
E-mail Web Master

Non Discrimination Statement