Background:

The popular holiday cactus is a true cactus, even through its appearance is different from the desert cactus forms. Native to the Brazilian rain forest, these plants have wide, flattened green stems that look like leaves (called segments) and produce colorful flowers.

Hybridization has so extended the bloom period of these plants that the names Thanksgiving, Christmas and Easter Cacti only give an indication of when they will start to bloom. One way to tell the difference between the species is to look at their segments. The "Thanksgiving" cactus (Zygocactus truncatacor) is also called the "lobster claw" cactus because the leaf segments have points at the tips of the segments; the "Christmas" cactus (Schlumbergera bridgesii) segments have smooth edges. The Easter cactus (Rhipsalidopsis gaertneri) has bristles on the sides of segments and at the tip of the terminal segments.

Red is no longer the only color found in holiday cactus. The color range extends from pure white forms through plants with varying shades of red and pink. You can also find cactus with peach, salmon, purple and orange flowers. Gold forms have also appeared recently.

Care:

These plants are usually blooming when purchased. Water lightly and put them in a cool spot with bright light, but not full sun. If the leaves start looking yellow, the light is too strong. For best bloom, keep them in a cool location (night temperature of 55 to 60 degrees F). The buds will drop off if the temperature is too high. Low humidity will also cause bud drop. These cacti may continue to bloom for months.

Begin to fertilize when blooming stops. Use a dilute fertilizer that is not too high in nitrogen once a month. A good formulation is 5-10-10 or 10-10-10. When warm weather comes, you can set the plants outside in a shady location--they can sunburn if exposed to excessive bright light. Despite the name cactus, they come from the jungles of Brazil and have the same habitat as orchids and ferns. If they must be kept indoors, filter the light and keep them in a cool location.

Holiday cacti tolerate being pot-bound, but for the health of the plants they should be repotted every few years. Add new soil and prune any roots that are brown and lifeless in the spring. The plant can be returned to the same-sized pot--plants in oversized pots with rich soil produce a lot of green leaves but very few buds.

Conditions for rebloom:

Flower buds will begin to set in September or early October. At this time, stop feeding the plant and reduce watering. If the plants have been outdoors for the summer, be careful to keep the plant in a cool location when you bring in the plants in order to avoid bud drop. The cacti need long nights to set buds. A brief exposure to light will not stop the budding process, but if there is a porch or street light outside the window and it shines long into the night, this may inhibit budding. It is recommended that the plant have 12-14 hours of uninterrupted darkness. Nighttime temperatures need to be around 50 to 55 degrees F for good bud set and flowering.

Problems:

Holiday cacti can be infested by scales or mealy bugs, but these insects rarely cause major problems. Wiping the leaves with alcohol can keep pests in check. Use a systemic insecticide for a serious infestation.

The main cultural problem to avoid is overwatering. Wait until the soil in the pot is quite dry before watering. This is especially important with the Easter form, which is very sensitive to overwatering.

Propagation:

Holiday cacti are very easy to propagate. In spring or summer, cut off a piece of the plant that has at least two segments. The more segments on the cutting, the larger plant you will produce--but limit the piece to 4 or 5 segments, as the small root system will not be able to provide adequate support and nutrients for too big a piece. Let the segments dry for a few days so that a callus forms. Then put the piece into damp sand or vermiculite. In about three to four weeks roots should have formed. You can then repot it into a small container filled with a light potting soil. This potting soil should be composed of about one third sand to avoid overwatering the young cactus.

By Cheryl Cadwell, URI Master Gardener