Kathy Adams, age 13, of Milwaukee, Wis., for her question:

HOW DOES A CACTUS PLANT REPRODUCE?

If you wish to sound Brandish, you may refer to these plants as cacti. Old Andy prefers a more simple lifestyle, so, in this case, let's call these fabulous plants cactuses. As a matter of fact, we need the plural form to answer today's question because there are hundreds of different cactuses.

All plants need water  but the cactuses are adapted to survive where water is scarce. In environments of this sort, competition is fierce and numbers are limited. The methods of cactus reporduction are like those throughout the plant world. However, there are built in restrictions to limit overpopulation.

A thousand or so different cactuses manage to survive in America's arid Southwest  plus numerous other plants. All of them are related to plant families of rainier regions. Through the ages, these special species have adapted to conserve moisture from shower to shower.    However, most of them still use the same method of reproduction they inherited from their remote ancestors.

Cactuses of the worldwide lily family may sprout new plants from bulbs or rhyzomes. Other types produce blossoms and seeds. Some depend on insects to pollinate their flowers  and all cactus seeds must be prepared to survive through droughts that may last through several years. When the rains finally arrive, they must be able to germinate and establish roots and shoots in a few days.

These basic patterns prevail throughout the plant world. But among the cactuses, the reproductive cycle must be crowded into a few short weeks. For 10 months or more, the parent plants barely survive. They have shallow, spreading roots to soak up moisture from the stingy showers and they try to conserve it in porous tissues under their leathery skins.

This is minimum survival  until a rare rainy season arrives. Then visitors arrive from far and wide to behold the wondrous beauty of the desert in bloom. Almost overnight, the various species sprout big, bright gorgeous blossoms, and numerous other plants spread flowery carpets all over the landscape.

In the desert, wind pollination may be a problem because parent plants tend to be widely separated. Insect pollination also is risky. The yucca, for example, depends upon a very rare moth. Though many cactuses produce attractive fruit to tempt birds and animals, seed dispersal is highly risky. Sometimes the rainy season is delayed  and the next generation of seeds must be able to stay dormant through several years.