Gilbert Wong, age 14, of Nogales, Ariz., for his question:

WHAT IS SPHAGNUM MOSS?

There are 350 different species of sphagnum moss. Found growing in swamps in most parts of the North Temperate Zone, sphagnum moss is also called "peat" moss.

Sphagnum or peat moss forms a dense mat and sometimes grows one foot or more high. It is soft and spongy and has no true roots but rather draws water through the walls of its stems and leaves.

The leaves and stems of sphagnum have the power to store large quantities of water for long periods of time. For this reason, it is valuable in greenhouses and gardens. Many rare plants, including orchids, are potted in peat moss to keep them from drying out.

Certain kinds of seeds are also sprouted on beds of chopped sphagnum moss. The moss is also often spread on the surface of the ground as a mulch in hot, dry weather.