In the Garden:
Upper South
November, 2007
Regional Report

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Right on cue, Thanksgiving cactus is covered in delicate blooms.

Welcoming a Holiday Cactus

Perhaps a holiday cactus has been passed down in your family, or maybe you became smitten when you saw some in bloom at the supermarket floral shop or garden center. Some are called "Thanksgiving cacti" and some are called "Christmas cacti," but although there are botanical distinctions between the various types, the easiest name to give one of these flat-leaved houseplants is "holiday cactus." Regardless of the name, we appreciate their incredible beauty and durability, either in our own homes or as gifts to friends.

Although they lack the spines normally associated with a cactus, these are true cacti, growing with flat, segmented, leaf-life branches called "cladophylls," which may or may not have long, serrated teeth on the edge. Appearing from mid-November until after Christmas, the showy, multi-petaled flowers come in shades of pink, rose, red, and white.

What's In a Name
Holiday cacti, in the genus Schlumbergera, were originally hybridized by William Buckley in Rio de Janeiro about 1840 and named after a Belgian horticulturist, Frederick Schlumberger. Some sources may call the genus Zygocactus. Officially, the Thanksgiving cactus is Schlumbergera truncata, S. truncates, or S. truncate, depending on your botanist, and the Christmas cactus is Schlumbergera x buckleyi. The actual blooming time has less to do with our holidays and more to do with growing conditions. In Europe they are known as crab cacti, and in their native Brazil they bloom in April and May, the normal fall season in the Southern Hemisphere.

As to specifics, S. truncata has four to eight prominent, sharp teeth at the margin of the foliar segments that are 1-1/2 to 2-1/2 inches long, and asymmetrical, tube-like flowers to 3 inches long, with spreading, pointed petals in a wide range of hues at the end of the segments. It tends to bloom in October and November.

Schlumbergera x buckeyi is similar, but it has spineless, scalloped-edged segments, tends to bloom later, and in fewer colors. For the record, there is also an Easter cactus (Rhipsalidopsis gaertneri), with leaf segments that are somewhat more three dimensional, having a thick ridge on one side; this cactus blossoms here in early spring with funnel-shaped flowers.

By Any Name
One of the reasons that holiday cacti are apt to be passed down in families is that they tend to be fairly indestructible, despite a few caveats. These cautions include being careful to avoid overwatering and to watch out for the tendency of branches to be easily knocked off the plant. Beyond those admonitions, holiday cacti generally thrive on benign neglect.

Holiday cacti need a well-drained potting soil and grow best when somewhat potbound, not surprising since these plants are naturally epiphytic in the jungles of Brazil, meaning they grow in the crotches of trees that supply support while rain and decaying organic matter supply nutrition. Because the top growth can become somewhat weighty, it's best to grow holiday cacti in clay pots rather than plastic. The porous nature of clay pots also helps to keep the plants from being overwatered.

Grow holiday cacti in a sunny window. After flowering, allow the plants to rest by withholding fertilizer, keeping them in a cool location (about 55 degrees F), and watering only when the top half of the soil is dry to the touch. After two months, move plants to a warmer site, increase watering, and fertilize every two to four weeks. Holiday cacti benefit from summering outdoors with a bit of shade during the hottest part of the day.

Coaxing to Rebloom
Getting holiday cacti to rebloom is a matter of day length and temperature. Regardless of the length of day, flower buds are initiated by temperatures lower than 60 degrees F. If the temperatures are warmer, the plants show a classic short-day response, initiating blooms with 12 hours or more of darkness. My plants summer outdoors and bloom is initiated before I bring them indoors, a response to both temperature and long nights. Continue feeding and watering regularly; research has shown that the old-fashioned practice of keeping the plant dry in fall decreases bloom set. Buds will drop if the temperature is too high or the light level too low.

Making More
To propagate holiday cacti, use a branch that has fallen off or snip off a branch with four or five leaf segments, dust the cut end in rooting hormone powder, and let the wound heal out of direct sunlight for about a week before planting. Fill a small pot with moistened potting mix, push the cut end about 1 inch into the soil, and keep it barely moist. There should be new growth in three to four weeks.


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