Tuberous begonias grow in partial shade but usually not so well in deep shade or full sun. Provide a well-drained soil. The plants need frequent watering and fertilization but excess of either causes flower bud drop. The plants are quite brittle, and staking helps them tolerate violent weather. The single female flowers are removed before seed forms to keep the plant blooming. The females are on either side of the double male flowers.
Scientific name: Begonia tuberhybrida
Pronunciation: bee-GO-nee-uh too-bur-HYE-brid-uh
Common name(s): Hybrid tuberous begonia
Plant type: herbaceous; bulb/tuber; annual; perennial
USDA hardiness zones: all zones (Fig. 1)
Planting month for zone 7: May
Planting month for zone 8: Apr; May
Planting month for zone 9: Mar
Planting month for zone 10 and 11: Oct; Nov; Dec
Origin: not native to North America
Uses: edging; hanging basket
Availability: somewhat available, may have to go out of the region to find the plant
Height: .5 to 1.5 feet
Spread: .5 to 1.5 feet
Plant habit: round
Plant density: moderate
Growth rate: moderate
Leaf arrangement: alternate
Leaf type: simple
Leaf margin: lobed
Leaf shape: cordate
Leaf venation: pinnate
Leaf type and persistence: not applicable
Leaf blade length: 2 to 4 inches
Leaf color: green
Fall color: not applicable
Fall characteristic: not applicable
Flower color: white; pink; salmon; orange; yellow
Flower characteristic: showy
Fruit shape: no fruit
Fruit length: no fruit
Fruit cover: no fruit
Fruit color: not applicable
Fruit characteristic: inconspicuous and not showy
Trunk and Branches
Trunk/bark/branches: not applicable
Current year stem/twig color: green
Current year stem/twig thickness: thick
Light requirement: plant grows in the shade
Soil tolerances: sand; acidic; loam; clay
Soil salt tolerances: unknown
Plant spacing: 6 to 12 inches
Roots: not applicable
Winter interest: not applicable
Outstanding plant: not particularly outstanding
Invasive potential: not known to be invasive
Pest resistance: long-term health usually not affected by pests
Use and Management
Tubers are started in February or March at temperatures of 65°F to 68°F. Start tubers, indented side up, on a layer of peat. When new growth is three to four inches tall, repot and cover the tuber. In central and south Florida the tubers are planted in fall for use as a cool season bedding plant.
Following a reduction in blooming and yellowing leaves, the leaves and stems fall off the bulb. The tubers are dug when the leaves and stems fall off. Do not break off the stems but wait until they fall off naturally. Injured bulbs should be exposed to air to allow the area to dry. Wash tubers and allow them to dry before storing. Dried tubers are covered with peat or sand and stored at 45°F to 60°F.
Propagation is by stem cuttings or by tuber division. Stem cuttings are made from surplus shoots which arise from the tuber. Stem tips may also be used. The cuttings are three inches long and are cut off just below a node. Sand may be used as the rooting media. Keep cuttings out of direct sun and in temperatures between 60°F and 65°F. Rooting occurs in five weeks. Tuber division is the other way to propagate the plants. Divide the tuber so each division has a bud and use a fungicide to prevent rot. Allow the pieces to dry several days then place them one-half inch deep in sand. The new plants develop more rapidly with bottom heat. Pinch off the first flower buds.
Thrips cause irregular reddish brown lines on the upper sides of the leaves. Spots form on the undersides of the leaves, especially along the main veins. The leaves may be deformed.
Black vine weevil grub eats the roots causing wilting and death.
Mites stunt the new growth.
Pests and Diseases
Begonias will be attacked by powdery mildew, especially if growing in the shade.
Leaf spots may be found on tuberous begonia.
Stem rot causes the stalks to rot and collapse. The rotted areas are usually black. Avoid crowding and remove any infected plants.