Tuberous begonias (unlike seed begonias) generally do best in a shaded part of the landscape. They may also need to be started indoors under lights to get off to a good start in northern temperate regions. If you wait until after the danger of frost to put them out into the garden, they might not flower until the fall.

Most, but not all, tuberous begonias are grown in containers. The ones that have pendulous growth are perfect for hanging baskets and window boxes in shaded locations. To insure a full season of flowers:

  1. Buy plants already in bloom from local greenhouses or nurseries. Use them as "annuals" and discard them after they are killed back by frost. This can be expensive but does not involve over-wintering the tuberous roots (stem tuber).
     

  2. If you store the stem tubers, you can start them indoors under fluorescent lights or in a bright window starting in later winter. These may then be transplanted into containers for moving outdoors after the threat of frost.

Tuberous begonias are rather tender and should be planted in a location that is protected from the wind and the late afternoon sun. A cool, partially shaded location is best which might receive early morning sun and dappled shade the rest of the day. Avoid heavy shade which will make the plants get "leggy" since they do require a few hours of sun to do their best.

Like most plants with underground structures (bulbs, corms, tuberous roots, etc.), these plants will not tolerate wet sites. This can lead to rots and loss of the plant. However, they are not very drought tolerant either so they need a soil or media that can be moist but not waterlogged.

Fertilize them with a liquid fertilizer in dilute solution throughout the growing season for best results.

Certain types of begonias such as Rieger or Rex begonias may be kept as houseplants since they maintain their foliage and bloom throughout the year. Tuberous begonias need to go through a dormant or rest period and will drop their foliage at some point in the year no matter how they are grown. Therefore, they are not suitable as houseplants.

In temperate zones, tuberous begonias will be killed back to the ground with the first few frosts. If they are left in the ground or containers during the winter, the stem tubers will also die. So, if you want to keep them from year to year, they need to be stored.

The idea is to allow the plant to store as much energy in the tuber to be able to produce a good plant the following spring. You can gradually reduce the watering late in the season and avoid fertilizing after Labor Day i.e. end of August. This should help encourage the onset of dormancy and the translocation of carbohydrates and sugars from the leaves and stems to the tuber.

After the first killing frost, carefully dig the tubers, cut the stems down close to the tuber and allow them to dry (cure) at room temperature or on a picnic table in the shade. Remove any remaining plant parts and carefully brush off any soil but don't wash them in water.

You can put the tubers in cardboard boxes filled with dry peat, perlite or vermiculite.

The most difficult part of storing bulbs, corms, tuberous roots or tubers is to find a place that maintains a temperature of about 40 to 50 degrees F. In the old days, farm houses had root cellars that fit the bill. Most modern houses have heated basements and are too warm and dry. If the storage area is too warm, it will encourage new growth or encourage rot. Houses during the winter have a very low relative humidity and this may cause the tubers to dry out.

An insulated but unheated attic, three season porch or a spare refrigerator in the garage might work just fine. Be sure to check the tubers occasionally during the winter to see if any rot or drying is occurring. If so, remove the rotted tubers immediately to prevent it from spreading.

 

  • If you over or under water tuberous begonias, they may drop their buds and stop flowering.
     

  • Powdery mildew may be a problem in highly humid areas
     

  • Botrytis blotch may cause a gray mold and rot where ventilation is poor and moisture is excessive.
     

  • Stem rot if the soil is too wet and poorly drained.
     

  • Occasionally bothered by mealybugs, whiteflies and aphids.

 

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.

 

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