There's probably no more appropriate gardening subject for Valentine's day than roses. The rose was designated the national flower by Congress in 1986. Roses are the favorite flower to express love, and at Valentine's Day the demand is never greater. Utah's two major rose growers, Utah Roses and Desarose, have been pruning, watering, fertilizing and nurturing their bushes to produce an abundance of the beautiful blossoms for the holiday.

Roses have a long, romantic history. It is said that Cleopatra met Mark Anthony on a bed of rose petals and Napoleon courted Josephine by bringing roses, her favorite flowers. Florists, as always, are delivering the message of love this holiday season. If you are fortunate enough to receive the coveted (and often expensive) flowers, here's how to make them last longer.Roses should never lack for water. If they are not in water when they arrive, immerse them in warm water for 20 minutes. Make a fresh, slanted cut, preferably with the stem underneath the water. Roses last longer when arranged in lukewarm with a preservative added. Preservatives are available at floral shops, and roses arranged by florists already have preservatives added. Keep the vase filled with water at all times.

Like other living plants, roses suffer from high temperatures and dry humidities. Keep them in a cool place out of direct sunlight. Lowering the temperature can double the life of cut roses. If an individual rose wilts prematurely, remove it, soak it in warm water for 20 minutes and give it a fresh cut as described above.

If you don't receive cut roses to enjoy, take heart. The 1991 All-American Rose Selections have been announced and will be available at local garden centers and nurseries later this spring. The All-American Selections for 1991 are: Sheer Elegance, a pink hybrid tea; Perfect Moment, a yellow/orange hybrid tea; Shining Hour, a yellow grandiflora; and Carefree Wonder, a pink landscape rose.

Sheer Elegance is a highly disease-resistant, hybrid tea rose of medium height. Its show-quality, non-fading blooms are soft pink with almond-colored edges and they have a mild to strong musky fragrance. It produces prolific blossoms with long, stiff stems and necks.

Perfect Moment features a unique yellow-based bloom with red tips. Its buds open in a slow spiral to show high-centered, heavy blooms that last well. The plant has dark green, leather-like foliage and excellent disease resistance.

The grandiflora rose, Shining Hour, is extremely floriferous with high-centered yellow blooms. The bush has good vigor with medium green, glossy foliage and an upright, dense habit.

Carefree Wonder is an everblooming landscape rose that requires low maintenance and is extremely hardy both winter and summer. Its colorful blooms are 41/2 inches across and feature rich pink petals with a creamy pink reverse side. The bush has exceptional vigor, rounded habit, and reaches a height of three to four feet.

A four-color brochure, "The Wonderful World of Roses" is available from All-American Rose Selection. The publication has information on rose selection, planting and care, and a listing of AARS public gardens throughout the U.S.

To order, send a check for $1, plus a self-addressed, stamped No. 10 (business-size) envelope to: Dept. 91W, AARS, 221 N. LaSalle Street, Chicago, Ill. 60601.

Whether the roses are a gift for Valentine's, a bouquet at Mother's Day or a plant for the yard, they are truly the queen of flowers. Enjoy one of the hundreds of different varieties as cut flowers or as a beautiful addition to your garden landscape.