Leaves and flowers fall off when the plant is under stress. Check that the plant is away from air and heat vents as well as drafty windows and doors and that the care routine is being followed in a consistent fashion.

• If stems and petioles (leaf stems) are stretched and drooping, improve the light. These large and sturdy plants need adequate light to develop a strong form. They need bright, filtered light with no direct sunlight in spring through fall. In the New York City area, light near an east-facing window is ideal, or slightly further from a south-facing window. In winter, the plant requires greater sunlight with a few hours of direct sun each day, as would typically be found pulled near to an unobstructed west- or south-facing window. Make transitions from one source of light to another gradually to reduce stress on the plant. Rotate the plant 1/4 turn each time you water it so that all sides of the plant will receive equal light.
• If leaves are dry on the edges, humidity is too low or heat is too high. Cane-type begonias are strongest when grown in normal home temperatures in the 60 to 70º F. range all year. The low end of the range is best at night and mid-range during the day. A relative humidity 40 - 60% is preferred to successfully grow cane begonias. Provide additional humidity by misting twice daily, standing plants on shallow trays filled with moistened pebbles and/or using a humidifier. A simple hygrometer kept in the area of the plant will help you to monitor air moisture.
• If leaves are soft, check that you are watering correctly and that humidity is not too high. Make sure to have good air circulation in the room so leaves don't stay wet and rot. Cane begonias can rot if the environment becomes too humid, above 60%. When the top inch of soil feels dry to the touch, water thoroughly in the morning using tepid water. Discard excess water from the run-off dish after 15 minutes. Allow to remain dryer in winter but do not let the potting medium dry completely. Avoid wetting the leaves when you water and dab away any errant drops that land on the leaves.

For more information on growing these plants see our Guide to Cane-type Begonias.

Courtesy of NYBG Plant Information Service