How to Grow Showstopping Tuberous Begonias

Botanical name:

Begonia × tuberhybrida

Hardiness Zones:

9-11; in colder zones (2-8), grow as annuals or overwinter the tubers indoors

Origin:

Tropical regions of South America and southern Africa

Growth habit:

Upright or trailing, depending on the variety

Height/spread:

Up to 18 inches tall (for upright types), trailing or spreading up to 24 inches

Exposure:

Shade to partial sun

Bloom time:

From late spring until frost. Once plants start blooming, they can flower continuously for up to four months.

Flowers:

Single, double, or ruffled flowers up to 6 inches across come in shades of pink, yellow, orange, red, white, or bicolors, some with picotee edges.

Foliage:

Leaves may be various shades of green, maroon, or chocolate brown and are usually pointed, with serrated edges.

Fun fact:

Tuberous begonias are monoecious, which means they bear both male and female flowers on the same plant. They are produced in clusters of three, with two smaller female flowers next to the larger, usually double, male flower.

Begonia tubers. Photo by: Stanislav71 / Shutterstock

When to plant:

Although begonia tubers can be planted directly outdoors in spring after the danger of frost has passed, they may not bloom until late summer or early fall in northern areas of the country. To speed things up, you can start the tubers indoors about 8 to 12 weeks before the last frost date in your area so they have time to develop before being moved outside. Once the weather warms up and nighttime temperatures are consistently above 50 F, the tubers can be transplanted into the garden.

Where to plant:

Grow in dappled sun or bright shade, in a spot protected from strong winds to avoid damage to the foliage and stems. Most varieties dislike high heat and hot afternoon sun, so they may suffer when grown in southern climates.

How to plant:

If you are planting tubers directly in the garden or in containers, set each tuber, round side down, about an inch below the surface of the potting mix or garden soil. To jumpstart growth, pre-sprout the tubers before planting by putting them in a warm, well-lit area for a few weeks until small sprouts appear.

How to start tubers indoors:

If you are starting the tubers indoors, place them about 1 inch apart in a shallow tray filled with moist potting mix. Place the tray in a dark room and water just enough to keep the potting mix moist, but not soggy. Once the tubers begin to sprout, move them to an area with bright light. Transplant them into the garden after the first two leaves have emerged and all danger of frost has passed.

Soil:

To avoid rotting of the tubers, begonias must be planted in well-drained soil. If you have a heavy clay soil that drains poorly, work in some compost or other organic matter before planting to improve soil aeration and drainage.

Spacing:

To ensure good air circulation, space plants about 8 to 12 inches apart in the garden and 4 to 5 inches apart in containers, depending on their size at maturity. Avoid overcrowding, which can lead to fungal diseases, such as botrytis and powdery mildew.

For more information about starting and planting begonia tubers, read this guidance from the American Begonia Society.

Do tuberous begonias like sun or shade?

They can tolerate a bit of both, but most prefer indirect, filtered light. Avoid direct sunlight, which can burn the foliage, or deep shade, which can cause spindly growth and poor flowering. Some newer varieties are more tolerant of direct sun exposure, especially if it's morning or late afternoon sun.

Do tuberous begonias come back every year?

Yes, as long as you dig up the tubers and store them indoors during their winter dormancy period. The tubers will not survive if left in frozen ground.

What is the difference between tuberous begonias and "nonstop" begonias?

The Nonstop® series of tuberous begonias are started from seed, rather than being propagated from tubers, and will grow and flower in just one season, producing large, double flowers that will bloom nonstop, as the name suggests. Although they are produced from seed, they will develop a tuber that can be lifted in fall and overwintered indoors.

Do tuberous begonias require staking?

Trailing varieties are meant to creep along the ground or cascade from containers, so they need no staking. Upright types, however, can benefit from staking to support the flower-laden stems and prevent breakage. When plants are 4 to 6 inches tall, place a narrow bamboo or metal stake in the soil a few inches away from the main stem and gingerly fasten the stake to the stem with plant ties or garden twine, adding more ties as needed as the plant grows.

Where do I buy begonia tubers?

If you plan on growing your begonias from tubers rather than from nursery-grown plants, you can often buy the tubers at local garden centers, but you’ll find a larger selection of plant varieties and bloom colors online from mail-order companies that specialize in bulbs. The best time to buy your tubers is in late winter or early spring so you can have them ready for planting season.

What are good companion plants for tuberous begonias?

Tuberous begonias are so stunning when in full bloom, they become the center of attention wherever you plant them. In mixed container combinations, team them up other moisture-loving, shade-tolerant annuals that will enhance rather than detract from their beauty, such as silver ponysfoot (Dichondra argentea), sweet potato vine, alyssum, and lobelia.

Can tuberous begonias be grown as houseplants?

Tuberous begonias will enter a dormancy period no matter where you grow them, whether indoors on a windowsill or outdoors in the garden, so they aren’t practical as year-round houseplants.