Regional Gardening Reports :: National Gardening Association

In the Garden:
New England
December, 2007
Regional Report

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If you can give a clivia the cold treatment it needs to flower, you'll be rewarded.

Some Like it Cool

It's the time of year when Thanksgiving and Christmas cacti are supposed to be showing off their lovely blossoms and heralding the holiday season. But some years they don't seem to understand their role. They are among a group of plants that have some particular requirements for initiating flowering. In the wild, all goes according to plan, but when we want them to flower inside our homes, it can require some finessing of their environment. Temperature and light and moisture are the main factors that you may need to manipulate.

Some of our most exotic-looking tropical houseplants depend on a period of cool temperatures to initiate flowering. In their native habitats, the temperatures drop in fall, providing a nice little rest for the plants, and then they begin active growth again, often flowering within a few weeks. Christmas and Thanksgiving cacti (Schlumbergera spp.), cymbidium orchids (Cymbidium spp.), orchid cacti (Epiphyllum spp.), and clivia (Clivia miniata) may not produce flowers if kept inside year-round at normal indoor temperatures. If you have one of these beauties and it's not flowering on cue, here are some things you might try.

Christmas and Thanksgiving Cacti
These plants bloom in late fall or winter, depending on the species. The common recommendation is to give them cooler, drier conditions and no light from sundown to sunrise beginning in the fall, say in October. Move the plant into a closet or room that's not used after dark or cover it with something that blocks all light. Even a brief exposure to lamp light may be enough to interrupt the required cycle of darkness.

Cool temperatures alone also can initiate buds, so if cutting out all light at night isn't practical, try keeping the plant outside during the summer until temperatures drop close to 40 degrees F, then bringing it inside to a cool room. In either case, once the buds show at the tips of the stems, you can move the plant to the living room in bright light but not direct sun.

I have two Christmas cacti, and to totally confuse matters my huge Schlumbergera flowers just fine sitting in a west window in my living room year-round. It's a good thing, too, because it's too big to move or cover. My other plant won't flower without the dark or cool treatment. I think they're just showing their individuality.

Cymbidium Orchids
Growing up to 4 feet tall and wide, standard cymbidiums are not your tabletop orchids. Nor are they as foolproof as some other types of orchids, such as moth orchids (Phalaenopsis). But they are drop-dead gorgeous when in flower, which can last for weeks. Day length is not an issue but these plants need very cool nights -- down to 45 degrees F. The newer hybrids, however, are more forgiving of temperatures about 10 degrees warmer. These "miniatures" reach only about 2 feet. I overwatered mine during the winter when they need to be kept barely moist, and lost it. Next time I'll choose a miniature that's easier to flower.

Orchid Cactus
Epiphyllums are a type of jungle cacti, and their huge, gorgeous pink, red, purple, white, or yellow flowers emerge at the edges of their flattened, fleshy stems, similar to Christmas cacti. The day-flowering types bloom April to June, and flowering is triggered by cool temperatures and darkness. Give them a treatment similar to Christmas cacti -- night temperatures of 40 to 50 degrees F during winter, and darkness after sundown. Provide bright light but no direct sun, and allow the soil to almost dry out between waterings. Keep them pot-bound, too, and be patient because a young plant can take three years to flower. This gives me hope for my three-year-old plants.

Even when not in flower, the long, dark green, strap-like leaves of this amaryllis relative make this an attractive plant. But the flowers -- in shades of orange, salmon, pink, yellow, and white -- are worth fussing over. Clivias benefit from life outside during the summer and fall until temperatures reach into the 40s. Or provide five weeks of chilling in the fall at 40 to 50 degrees. They also flower best when pot-bound and at least three years old. Their roots are sensitive to too much moisture, so fir bark is a good potting medium.

High-phosphorous fertilizer will encourage better flowering of all these rather long-lived plants. They deserve plenty of elbow room and a prime spot when in flower.

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