Summary: The tuberous begonia is a popular flowering potted plant. As with all things growing questions arise. Below are some questions and answers from readers on the growing and care of the tuberous begonia.
Question: Last year my tuberous begonias had a heavy attack of mildew which nearly ruined the plants. What should I do about it if this condition appears again this season? Will my tubers be any good for planting again?
Answer: Mildew is encouraged by an excess of nitrogen which causes soft rapid growth, by keeping the foliage wet at night, and by close planting in sheltered locations.
Soil that contains less nitrogen and more potash will help to make the plants more resistant to the fungus. Set the plants farther apart and in a location where air currents will tend to dry off the foliage. Do not water in the evening.
The soil and air is literally full of mildew spores during warm weather and the best control is to try to discourage the growth of the spores on the plant leaves.
You cannot hope to prevent spores from reaching the leaves, but by keeping the leaves dry and air circulation around them, the growth of the spores is discouraged.
Also, spraying or dusting plants is helpful to protect them from infection. Dusting sulfur applied at regular intervals to the foliage is effective. It is best applied in the early morning in clear weather.
As the sulfur vaporizes it kills the spores of the mildew that are present on the leaves. The tubers retained from last season are as good as any to plant next spring.
Question: Several years ago I grew tuberous begonias with great success, then I had trouble with buds dropping off, so I gave up. I would like to try again. AW, PA.
Answer: Buds often drop in poorly drained soil or in hot muggy weather. The soil should be moist but make sure it never gets waterlogged.
==>> Read: Tuberous Begonias Not Impossible
Question: My tuberous begonias come up all right and grow for a while, then they rot off at the ground and won’t come up again. How can I prevent this?
Answer: Tuberous rooted begonias are easily grown and should bloom from early summer until frost. They require shade, such as under trees, behind shrubs, or on the north side of a building.
Besides shade they must have rich soil and a continuous supply of moisture. In midsummer when the humidity is low, a fine spray of water should be given the leaves about mid-day each day.
Lack of moisture in the air around tuberous begonias is the greatest problem in growing them to perfection. The soil itself need only be kept moderately moist.
Good drainage is required and unless the free water runs off promptly the plants may rot at the surface of the soil as you have described.
At the first sign of any decay, sprinkle the soil with water to which a all purpose fungicide has been added to each gallon of water and give the plants all the ventilation possible.
Question: What causes buds of tuberous begonias to drop?
Answer: Bud drop on tuberous begonias may be due to several factors, generally of a physiological nature. Overwatering and underwatering may both be factors.
Tuberous begonias need to be always moist, yet not wet, and excellent drainage is necessary.
Watering too late in the afternoon may be another cause. It is best, therefore, to water in the morning. Still another difficulty, though not within our control, is that of a series of sudden hot days followed by some cold days and nights.
Question: Please tell me how to, care for tuberous begonias through the winter and how to start them again for the next season.
Answer: When light frost kills the foliage of the tuberous-rooted begonias, cut off the stem three inches above the soil. Lift the tubers with all the soil that will adhere to the roots and place them in a cool, dry place.
When the soil is dry, in about two months, clean the tubers, dust a little Sevin on them and store them in dry peat moss. If they show any signs of shriveling, sprinkle lightly with water.
In February or March they may be planted to start a new season. Another method is to clean the tubers completely and spray with an anti-wilt substance such as Wilt-Pruf before storing in peat or vermiculite.