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.