Holiday cactus: Tips to ensure best bloom season

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Q. Every autumn my “crab claw” (Thanksgiving) cactus plants develop a load of flower buds. As the first ones are opening, I move the plants from their regular location at a bathroom window to display areas in the dining and living rooms, which are kept at cool room temperatures even in winter. My problem: Behind almost every main flower bud there are one or two secondary buds. Every year, as the main flower fades, the secondary buds shrivel and drop off. Why do these secondary buds dry up?

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A. It is not unusual for plants that form an excessive number of flower buds to shed some of them.

Sudden changes in temperature, or in light and soil moisture levels, can also instigate or compound the shedding of some flower buds. For the best possible bloom season from a holiday cactus, once buds appear on a plant it is best not to move it.

Where it is possible, setting the plants outdoors in filtered light for the summer and beginning to reduce watering around mid-August before bringing them back indoors (when temperatures approach 5 C) will set the plants up for the best possible season of bloom.

Q. Through the summer and early fall, our fully sunny back garden suffered an infestation of whitefly on the dahlias, hydrangea, clematis and begonia plants. How can I prevent a repetition of this next year?

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A. Whiteflies that infest and weaken outdoor garden plants by sucking out their juices do not survive freezing temperatures.

Infestations as heavy as you describe must have begun early in the season, most likely introduced to the garden on acquired transplants that were already infested.

Early entry into the garden would have allowed populations to build, with many generations of the flies over the season.

To prevent a repeat infestation, carefully inspect plants before bringing them home. Look for tiny, dark eggs and scale-like larvae on leaf undersides.

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