GARDENING : HORSETAIL HAS PULLED ITS WEIGHT SINCE PREHISTORIC TIMES.

Byline: Joshua Siskin

Long ago, it was eaten by dinosaurs. Today, it is an ingredient in medications that lower cholesterol. Throughout human history, it has been used for scrubbing kitchen utensils.

Known commonly as the horsetail or scouring rush, this plant has emerged as one of the species that is increasingly recommended by garden and landscape designers in search of high-concept or minimalist designs. These are designers who utilize plants for their shapes, architectural lines, foliage color and durability rather than flowering characteristics.

Horsetail consists of many reedlike, segmented green tubes that grow straight up to a height of 4 feet. Attractive black and gray bands are found at both ends of each segment. It is often planted in long, narrow planters and makes a strong design statement.

It does best in half-day sun to light shade. Some people plant horsetail in full sun, which, in our hot valley, means that it will appear yellow-green as opposed to the emerald green color it shows when sun-protected. This yellowing can be observed in a long, south-facing bed of horsetail growing behind Linens 'N Things on the corner of Riverside Drive and Woodman Avenue in Sherman Oaks.

Horsetail thrives where water is plentiful, but it will grow well enough with a single weekly watering. It is the ideal plant for naturalizing - which is a polite word for ``taking over'' - an area. It spreads by underground fleshy stems called rhizomes; rhizomes are found on many plants, from irises to agapanthus, from ferns to Bermuda grass.

If you have a moderately shady area with heavy, poorly drained soil where nothing will grow, you should consider planting horsetail. It is impervious to cold and grows wild as far north as Canada. Just don't plant it with ferns, azaleas or, for that matter, any other plants, since the horsetail will surely, within a few years, bury them all.

It is thought that giant horsetail trees, reaching a height of more than 10 feet, lived at the time of the dinosaurs and were grazed on by vegetarian dinosaur species.

The garden variety of horsetail - Equisetum hyemale - has accompanied human beings in all their wanderings because of its abrasive and medicinal properties. No plant is more concentrated in silica than horsetail. It was used by the pioneers for scouring their pots and by housewives for polishing their pewter. Even today, campers looking for a way to clean their cooking utensils grab fistfuls of horsetail, which is often found growing next to streams, to do the job.

The silica in horsetail is highly soluble in the fluids of wounds and has been used to stop bleeding and heal broken bones. Horsetail extract is also found in herbal products that are recommended for people suffering from incontinence or high cholesterol.

One of the most popular landscape designs for water-thirsty climates incorporates fountain-shaped plants with low water requirements. The idea is to suggest a vista of spouting fountains as a counterpoint to dry surroundings.

Such fountainlike plants include fortnight lily (Dietes vegeta), flowering on and off throughout the year in full sun; New Zealand flax (Phormium tenax), with spear shaped leaves in green, bronze or purple, for full to partial sun; Juncus patens (California gray bush), a rushlike arching plant with brown-banded leaves, for full or partial sun or shade; and ornamental grasses for full or partial sun such as purple fountain grass (Pennisetum setaceaum ``Cupreum''), which has purple leaves with wheatlike inflorescences, and sheep fescue (Festuca ovina ``Glauca''), a small mounding plant with silvery-blue foliage.

A landscape with such plants often includes a winding swath of smooth, gray stones, suggesting a dry stream bed, or, in the symbolic Japanese mode, the movement of water.

Necessity has become the mother of invention in contemporary California landscape design. With the continuing uncertainty about the availability and price of water, many people are opting for drought-tolerant landscapes that use only 10 percent to 20 percent of the water required by lawns. In the process, people are making a design statement by utilizing plants whose strong architectural lines and shapes - as opposed to flowering capacity - take center stage.