University of Vermont Extension
Department of Plant and Soil Science
Dr. Leonard Perry, Extension Professor
University of Vermont
If you are looking for a colorful, attractive flower to grace your
garden or provide colorful containers, try the tuberous begonia. It
is easy to grow, blooms well in the shade, needs moderate care, and
will reward you with a lovely display of blooms all summer long.
Tuberous begonias come in shades of white, pink, red, yellow,
orange, and salmon, as well as bi-colors. If they have a darker edge
to the petals they are called "picotee." Double flowers are male,
and single flowers female. The large flowers are usually double and
may be six inches or more in diameter. Plants generally grow 12 to
18 inches tall.
Depending on the cultivar (cultivated variety), plants may have
camellia, ruffled, or rosebud type flowers. The hanging basket types
such as the Illumination series have smaller, more numerous flowers
than the more erect types.
“Nonstop begonias”, which were first developed in Germany, are
perhaps the most popular upright series, with double blooms in many
colors. They are so named because if given some light during the
night during winter months (indoors or in a greenhouse, of course),
they will bloom nonstop. Other upright ones include the Panorama
series with smaller but more flowers, and the Ornament series with
burgundy leaves and red or pink flowers.
Many people don't realize that begonia flowers can be eaten! The
lemony sour flavor goes well with fruit salad, salads, yogurt, or
ice cream. Just make sure if you are going to eat flowers, you don't
use any pesticides on the plant.
Tuberous begonias grow best in a location that has partial to full
shade, but bright light. They don’t like dense shade. An ideal
site might have morning sun, or sunlight filtered during the day by
trees. They prefer a light, rich, well-drained soil. Prepare the
site by incorporating organic matter, such as peat moss or compost,
into the upper 8 to 10 inches of the soil.
If starting them yourself, purchase only high quality, firm tubers.
Unlike other begonias, these grow from this bulb-like structure.
Tubers can be started early indoors four to eight weeks before the
frost-free date for your area. Plants usually flower about three
months after planting tubers.
Use flats or pots filled with equal parts of moist peat moss and
perlite, or three parts soilless potting mix with one part builder’s
sand . The depressed or hollowed (concave) side of the tuber should
be facing up. The tubers should be sprouted in the dark at about 70
degrees (F). If the air is cooler, you can place pots on a heating
As soon as shoots develop, cover the tubers with more potting mix,
and move to a bright location such as a sunny window. The young
plants should not be transplanted outdoors until all danger of frost
has passed. If started indoors, gradually acclimate them over a few
days to temperatures and the brighter light of outdoors.
When planting outdoors, place them at the same depth as they are
growing in pots. Tubers rot easily when planted too deep. A
minimum of 8- to 12-inch spacing apart is recommended to allow the
plants to fill out properly. After planting, do not cultivate around
the root system or the fibrous roots will be damaged. Since the
stems are quite brittle, they often need staking, especially in
Plants should be watered when the soil begins to dry. The tubers
will rot if they are overwatered and soil remains soggy, or stems
may snap off at the base. Try to water in the morning if possible so
that any moisture that gets on the foliage will have time to dry
before evening. Wet foliage increases the chance of disease.
Feed every two weeks with a general purpose liquid fertilizer, or
according to label directions. Use half strength when the plants are
young and just sprouting. You may also use a slow or
controlled-release fertilizer in the final beds or pots.
They also make excellent patio plants in containers. Start tubers in
4- to 6-inch wide pots, or if buying such, transplant when
well-rooted into 7- to 10-inch pots. You may even put two or more
plants in larger pots, window boxes, or long planters.
Pick flowers off as the edges turn brown to prevent them from
rotting and starting disease. If plants are dry and stressed, and
the leaves turn brown, the cause may be too much sun, too much heat,
or too little water. If upright plants are leggy, this means that
they are getting too little light. Too little light for hanging
basket cultivars will make them grow upright and not cascade over
the container sides.
Yellowish leaves indicate more fertilizer may be needed. White
growth on leaves is powdery mildew disease. Fungicides can be used,
but wider spacing and more air circulation may be all that is
If you’ve brought plants indoors before frost, force them into
dormancy by gradually watering less often. Remove the stems and
leaves once brown and dry. If left outdoors, after the first fall
frost, dig the tubers and remove the foliage. Dry the tubers for a
few days, and store them overwinter by placing them in dry peat moss
or sawdust in a paper bag at about 50 degrees. Give them some water
in late March or early April, bring into bright light when growth
resumes, and start the process again.