Christmas cactus plants are attractive houseplants that bloom in December, just in time for the holidays. Christmas cacti are considered tropical plant types that require extra care, unlike their desert relatives, which don't need as much care to grow and flower. This particular cactus needs proper care to bud and flower each year. There are a few reasons why the flowers will wilt, which will cause the buds to drop as well.
During winter and fall, keep the Christmas cactus in a window with direct sunlight, but during the spring and summer, the plant needs indirect sunlight or filtered sun. Plants need at least 13 hours of darkness daily starting in mid-September and continuing through mid-November or the buds will not form, or they will form and drop. However, if you keep the cactus in a room where the temperatures are 55 degrees Fahrenheit, it doesn't need a full 13 hours of darkness.
Leaves on the Christmas cactus will wilt when the plant doesn’t receive enough water. Dry soil conditions will also cause the buds to drop. The soil needs to be moist during summer and winter, but dry to the touch in fall and spring before adding water. When watering the cactus, avoid getting water on the leaves. Use water that is room temperature to avoid shocking the plant roots, which can cause the plant not to bud and flower.
House temperatures between April and September should be between 70 and 80 degrees Fahrenheit during the day. When buds set during fall, temperatures above 90 degrees Fahrenheit will cause the buds to drop. Night temperatures between 55 and 65 degrees Fahrenheit are needed for good leaf growth and bud formation. Plants should be kept away from drafts, cooling vents, heating vents and fireplaces; the extreme temperature changes will cause bud drop.
Apply a water soluble cactus fertilizer once a month from March to May when the plant is actively growing. Stop fertilizing the Christmas cactus, though, in June and July, but fertilize again in August and September. Do not fertilize the plant in December and February. Use cactus fertilizer at one-quarter of the strength recommended on the package.
Turning on lights in a room or car lights that shine in the window where the Christmas cactus is kept will interrupt the number of hours of darkness the plant needs during its dark period. This problem will cause buds to drop. If the plant is in a room where these conditions exist, move the plant to a new spot in September, perhaps a dark closet, and leave it there for eight weeks before returning it to its original location.