Frances Palmer, age 15, of Jackson, Miss., for her question:

WHAT ARE SCOURING RUSHES PLANTS?

Scouring rushes are plants that are also called jointed horsetails. The plant's proper name is equisetum. In ancient times this plant was especially abundant in warm, moist swamps and it grew to heights of 100 feet.

There are only 25 species of the rush like plants growing today. The remains of the ancient plants helped to form the coal beds that were laid down at that time. Today's plants prefer cool climates.

The equisetums are spore bearing but not flower producing plants.

Creeping stems growing deep underground are perennial. It is difficult to clear a field of equisetums once they have become established.

The rough stems of some of these plants hold a very high percentage of silica, a sand like material that is used for polishing wood ox scouring metal. For this reason they are given the name of scouring rushes.