 | Tuberous Begonia Care Informaton Sheet
Hooper's Garden Center |
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Background
Tuberous begonias are popular for their beautiful flowers which come in a variety of colors and forms.
Red, orange, yellow, white, salmon and pink blooms may be single or double; they may be plain, ruffled or toothed;
their petals may have margins, crests or blotches of contrasting color. Tuberous begonias bloom throughout the
summer, thriving in shady spots where few other plants with long bloom periods and showy flowers can grow.
They are often used as container plants on patios and porches, in hanging baskets, and as bedding plants.
American Hybrids varieties offer the best plants and the latest varieties.
Tuberous begonia species are native to tropical South America and southern Africa. Most varieties available in
garden centers or though catalogs are hybrids with complex parentage, but all share the same cultural requirements
Starting Begonia Tubers
It is wise to have your tubers well established before hot weather arrives. A good strain is essential for best results.
For the gardener who desires having choice plants and the latest varieties, make certain you choose
American Hybrid varieties.
In mid to late February, purchase tubers or start those you have stored. Tubers started in February should begin to
bloom in June; those started in March or early April should bloom in July. Plant the tubers in a flat of peat moss or
loose soil mix. If the stored tubers showed no signs of disease, you can use the same medium in which they were
stored. Otherwise, fill the flat with fresh peat moss or loose soil mix to at least 2 ½” deep. Find the upper surface of
each tuber, the side with the depression or hollow. Plant the tubers hollow side up in the flat, so the peat moss or
loose soil mix just covers them.
During this time, the tubers are very susceptible to rot, so it's important to keep the medium fairly moist, but not wet,
and do not to allow water to accumulate in the hollow. Place the flats where the temperature is between 50 to 70°F.
Bright to indirect light is recommended. Ample light is required after the buds appear. Heat Mats set at
70-75 degrees F will also benefit tuber growth.
Roots will develop from the bottom, sides and top of the tuber, and stems will sprout from the top. After about one
month, the stems will be 1" tall. Once they have reached this size, it's time to repot the tubers into larger containers.
Five to six inch pots are ideal. Providing supplemental lighting or moving the plants to a brighter location will help form
short, sturdy stems rather than tall, leggy ones.
Small tubers will produce small plants; large tubers, large plants. Flower size is not affected by tuber size, but by the
number of stems on each tuber. If you would like bigger flowers, thin the shoots when they're about 3" tall. Small
tubers should have two or three stems, large tubers three to six stems, so pinch off any extras. Some varieties,
such as those used in hanging baskets, are grown for quantity of flowers, not for large blooms. These varieties
should not be thinned. Hanging varieties bushy and bear lots of smaller flowers, especially if the tips of the stems
are pinched in May or early June.
To acclimate the plants to outdoor conditions, begin hardening them off about two weeks before the last frost date
(End of May). Move the plants outdoors on a warm day to a shaded, protected place. Bring them back in before
temperatures cool off at night. Continue this process, gradually moving them out into brighter light and exposing
them to more wind, but continue to bring them in at night. Once the weather has settled, the soil is warm, and all
danger of frost is past (usually by early June in most of Montana), transplant them to hanging baskets on the porch,
containers on the deck or patio, or to there spot in the garden.
Hooper’s grown tuberous begonias are generally available by mid May.
Planting
Choose a site for tuberous begonias somewhat protected from wind, where the soil is well-drained, and plants will be
shaded during most of the day. Early morning and late evening sun will not harm them. They require good indirect or
dappled light at other times.
Although tuberous begonias must be grown in well-drained soil, they are not drought tolerant, so it's important to
water them when rainfall has been inadequate. Begonias need to be moist (not wet) at all times. If they're growing
in the shade of trees or in containers under a roof, you must pay even more attention to keeping the soil properly
moist. Moss-lined or Cocoa Fiber wire hanging baskets work particularly well to provide adequate drainage. Tuberous
begonias are fairly heavy "feeders", so fertilize with a dilute balanced fertilizer throughout the growing season for
best bloom and growth.
Storing Tubers
Tuberous begonias will enter a dormant period no matter how they are grown, whether in a greenhouse or outdoors,
so they are not suitable as year-round houseplants. (Some others, such as Rieger begonias, are a better choice as
indoor flowering plants). During the dormant period, begonia tubers must be stored indoors. Left in the ground
during a Montana winter, they would be killed.
To prepare the tubers for dormancy, gradually reduce watering and stop fertilizing at the end of August. Some
gardeners may choose to remove any flower buds that form in September to encourage dormancy and the
storing of energy in tuber.
Dig begonia tubers when the foliage starts to yellow, or after the first killing frost. Cut the stems to about five inches,
and allow tubers to cure (dry) indoors at room temperature, out of direct sunlight, until the remaining stem pieces
are dry and loose. Pull off stems and any roots or soil, but don't wash the tubers.
Store the tubers in a perforated plastic bag filled with peat moss or perlite in a cool, dark place. The ideal storage
temperature range is 40°F to 50°F, much cooler than most basements. An insulated but unheated attic or
three-season porch may be cool enough. A spare refrigerator can be an ideal place to store tender bulbs and
other bulb-like plant parts, such as tubers. Check the tubers occasionally for rot, softening or withering, and
discard bad tubers immediately.
Propagation
Unlike potato tubers, you can't cut begonia tubers into pieces to produce more plants. Although some growers
divide begonia tubers, they must make the divisions when the plant is actively growing, and the tuber pieces often
become diseased and rotten.
A better way to propagate tuberous begonias is to root cuttings. If you thin out the stems when they are
about 3" tall, you can use those cuttings. Some gardeners cut a small piece of tuber with each shoot to
increase the chances of the stem rooting, but the wound on the tuber may allow disease-causing organisms
to attack the tuber.
Propagating begonias is very time consuming and requires diligence and dedication. Most gardeners today
either save their tubers or purchase new ones each spring. Hooper’s grown tuberous begonias are generally
ready for sale in mid May.
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