Tuberous begonias are prized for their huge, ruffled flowers that come in many luscious colors from white to yellow, apricot, orange, pink, rose and red. They’re hybrids of several tropical species, so they’re outdoor hardy only in frost-free zones, but in other regions you can grow tuberous begonias in summer garden beds and containers.
The fleshy, flattened tubers produce upright or pendulous stems with handsome, angular, deep green leaves. Tuberous begonias bloom for months, bearing single, semi-double or fully double flowers. Where not hardy, treat tuberous begonias as annuals and discard them when frost arrives, or dig and store the tubers in a cool, fairly dry location over winter.
Common name: Tuberous begonia
Botanical name: Begonia × tuberhybrida
Plant type: Summer-flowering bulb (tuber)
Zones: 10 or higher as outdoor perennials
Height: 10 to 18 inches
• Sun: Partial shade
• Soil: Loam or sandy loam with ample organic matter
• Moisture: Evenly moist but well drained
• Mulch: None
• Pruning: Clip off flowers as they fade.
• Fertilizer: Fertilize every other week with diluted soluble fertilizer.
Pests and diseases
• Powdery mildew, stem or tuber rot, slugs and snails
• Hundreds of tuberous begonias have been selected for flower color and form, growth habit and foliage color. You’ll find the best selections in specialty plant catalogs at garden centers.
• The Nonstop Series begonias bloom all summer with yellow, orange, pink and scarlet flowers; they’re ideal for window boxes and patio pots.
• The Nonstop Mocca Series begonias have chocolate bronze foliage and a range of flower colors.
• The Illumination Series begonias feature pendulous stems with large semi-double flowers in a range of colors; they’re perfect for hanging baskets or window boxes.
• Tuberous begonias grow best where summers are somewhat cool and humid, like the maritime Pacific Northwest. In hotter, drier regions place them in the coolest spot you have and be sure to keep soil (or potting mix) evenly moist.
• If you enjoy a challenge, you can grow tuberous begonias from their dust-like seeds, but be aware that the process takes six months from seed to flowering plant.
• For a longer flowering season, get tubers started indoors in pots several months before the final frost date; plant outdoors only when temperatures have warmed fully.
• Float a fully opened tuberous begonia flower and a leaf or two in a crystal bowl for a simple but elegant centerpiece.
All in the family
• Tuberous begonia is a member of the begonia family (Begoniaceae), which contains the genus Begonia and just one other genus—the single-species Hillebrandia sandwicensis of Hawaii.
• There are nearly 1,500 species of begonia, mostly native to the tropics.
• Other popular begonias for gardens and houses include fibrous-rooted varieties, which are popular as annuals; Rex-Cultorum types, noted for beautifully patterned foliage; and winter-flowering types like Rieger begonias that make lovely flowering houseplants.
Where to buy
• Eden Brothers, edenbrothers.com
• McClure & Zimmerman, mzbulb.com
• White Flower Farm, whiteflowerfarm.com
Photos courtesy of Proven Winners at provenwinners.com.