The care information provided in this section represents the kind of practical advice is available for all the plants in this web site if you subscribe to the monthly customized newsletter Yardener’s Advisor.
Ideally, tuberous begonias should get 1 inch of water a week from rain or from a watering system. Check soil moisture regularly, especially in containers. If the soil is somewhat dry to the touch it's time to water thoroughly. Water them in the morning. Use a sprinkler or soaker hose to gradually penetrate to a depth of 10 to 12 inches. Avoid whenever possible purposely wetting the stems or foliage, to discourage disease. For information on products see the file on Choosing Watering Equipment
Tuberous begonias are heavy feeders. Feed them before flowering begins for good leaf and stem growth. Thereafter offer them a light feeding of an all purpose liquid or granular fertilizer about every 3 weeks or so. This will encourage large blooms and firm tubers. Stop feeding when plant growth slows in the fall. When moving begonias to new containers, don't feed them until 3 weeks after they've become used to their new surroundings.
Mulching and Weed Control
Mulching controls weeds, conserves soil moisture, and keeps soil from splashing up on the flowers. Spread a 2 to 4 inch layer of shredded bark, chopped leaves, wood chips or other attractive organic material on the soil around the tuberous begonia plants. Hand-pull weeds to avoid damaging fine roots near the soil surface. For more information see the file on Using Mulch
Propagation and Winter Storage
Tuberous begonias reproduce themselves by growing more buds on the mature tubers. To acquire more begonia plants divide these tubers. After the main stem has died back naturally, but before a killing frost, carefully dig the tubers from the ground with a spading fork. Then pack them in moist sand or vermiculite and store in a cool (35° to 50°F.), slightly humid place. Check the soil moisture level occasionally. In February or March, cut tubers into pieces, leaving an "eye", or bud, on each piece. Plant them in pots or trays, as described above, to start them for the new season.
Plants with stems over 5 inches high should be staked. Insert stakes at least 3 inches away from the tubers to avoid damaging the roots, and tie stems to them with soft rag strips. Remove spent flowers to prevent mold growth. In the fall, as the plants go dormant, they will drop leaves and stems. Remove these promptly to discourage tuber rot. When storing tubers, inspect them carefully and discard any that are not firm and clean.