When you think of holiday plants, Christmas trees and poinsettias come to mind. So do Amaryllis, one of those crazy bulbs that never seem to bloom right at Christmas, but make you feel in the holiday mood even if they pop forth in February.

The plant is actually a true cactus. If you look closely where the leaf segments join each other, you'll see the fine hair-like spines. All cacti have these, though some of them are more pronounced and sharper. You really have to work hard to poke these into your skin; they generally bend and break.

Most people equate cacti with deserts and Arizona. Cacti are, by nature, a group of plants that tolerate hot, dry conditions with little water throughout the year.

The Christmas cactus is an exception.

This plant is native to South America and can be found growing high in the branches of trees right next to orchids and bromeliads. Roots are mainly used to attach the plant to a tree. In short, this cactus is a tropical plant.

A short digression: there are Easter and Thanksgiving cacti. Each is technically a different genus or species. The scientific genus of the Christmas and Thanksgiving cacti is generally regarded as Schlumbergera, named after Frederick Schlumberg, a Belgian horticulturist who is credited with discovering the plant. Easter cactus belongs to the group Hatiora, named in honor of Thomas Hariot, a noted mathematician from early 1600s.

Now, a smart person will quickly realize that "Hatiora" and "Hariot" have a couple letters mixed-up. Someone years ago named another group of plants after Hariot, and so, the name for the Easter cactus had to be changed, so they chose an anagram of his name.

Anyway, the average Joe is going to have a hard time distinguishing between Christmas, Thanksgiving and Easter cacti as they can bloom just about any time they want. Your Christmas cactus can bloom in April and your Easter one in December.

Blooming is based on one of two factors, which may be interrelated or can stand-alone: temperature and light.

In nature, high up in the trees, the night temperatures can drop into the low 50s. The day lengths also start dropping, reaching the point in October and November where we might be experiencing more darkness than light. Both of these factors can trigger the flower buds of the Christmas and Thanksgiving cacti.

Which is exactly what you need to do make your plants bloom.

First, place the plant in a room that you can allow to get cool at night, in the low 50s cool. That may mean extra blankets or snuggling closer.

The other goal is to reduce the light. That's the same "tricking of nature" that you do with poinsettias to get them to bloom. If you can't stand the cold night temperatures, at least place the plant in a dark room. Bright light during the day is a must; absolute darkness is as equally necessary.

Of course, all this should be done starting in late September or early October. If you don't, your plant ends up blooming for you in February, March or April.

It's the lack of high humidity in our homes that causes the flower buds to fall. Misting doesn't really help. Put the plants in humid room or near a humidifier to make them last longer.

To grow the plant, try to match nature's conditions. High humidity, a loose well-drained soil that barely holds water and partially filtered light is the best. A bathroom is a great place for the holiday cacti especially if there is natural light. The worst thing to do is to view them as desert cacti. That will kill them. Literally.

During the summer, consider taking the plants outside and hanging them from tree branches. Water and fertilize regularly and you'll find the cacti responds favorably. Keep it outside until mid-October to help set the flower buds.

David Robson is an Extension Educator, Horticulture, at the Springfield Extension Center, University of Illinois Extension, P.O. Box 8199, Springfield, IL 62791. Telephone: (217) 782-6515. E-mail: drobson@uiuc.edu

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