SHOWBIZ ROSE

For two years it was known simply as 81R42 - hardly a becoming title for one of the world's most beautiful roses and the most outstanding specimen, by far, in this year's All-America Rose Selections (AARS) awards.

Now officially named ''Showbiz,'' 81R42 was recently declared the AARS award-winner for 1985. The bright scarlet floribunda so stole the show at the 23 trial grounds around the country that the winner was a foregone conclusion long before the 30-month trial period was over. In fact, for just the sixth time in the 49-year history of the judging, only one rose received an award this year.

The name Showbiz indicates the rose's brightness and prodigious flowering habit. But it barely hints at its beauty.

Showbiz is everyone's idea of the classic red rose. It's ''the flower you give to your sweetheart on her birthday or when all else fails,'' according to one judge. It's a full-blown floribunda, producing masses of brilliant scarlet blooms with an occasional hint of orange from spring through fall. The plants are bushy, growing to about 3 feet in height.

Like all the newer floribundas, Showbiz produces large flowers, averaging 21/ 2 to 3 inches across, each with 28 to 30 petals. The color holds true throughout the life of the flower.

A full decade ago, the German hybridizer, Mathias Tantau, looked at two roses , Dream Waltz and Marlena, and pondered what their offspring might be like if they were crossed. They were both outstanding roses in their own right, so the chances of some markedly superior specimens turning up among the progeny looked reasonable.

Mr. Tantau crossed the two and sowed the resulting seed in his greenhouse.

Several hundred seedlings resulted and grew to produce flowers with a wide range of color and size. The overwhelming majority proved indifferent, which is only to be expected in any breeding program. But a handful looked promising and were retained for further testing. Of these, Showbiz, then only a number in the breeder's notebook, began to exhibit the traits the experienced Tantau eye was looking for.

The rose was first exhibited in Europe and then Japan. In 1981 it crossed the Atlantic and was entered in the All-America trials as 81R42, its only identification for the next 21/2 years. In January of 1983, the judges' tallies were totaled and the winner, obvious even to laymen visiting the trials, officially chosen. Six months later, the rose was named and entered into the records as Showbiz.

An AARS award-winning rose is chosen two years before the official announcement so that the major nurseries involved in growing rosebushes for the wholesale trade can begin production. As a result, Showbiz will be freely available through local nursery outlets for the 1985 spring planting season.

Meanwhile, the rose can be seen at any one of the 123 AARS certified rose gardens around the country. It will be tagged ''Showbiz,'' or, in some cases, merely ''81R42.''

A free illustrated pamphlet, ''Roses Are for You,'' can be obtained by sending a stamped, self-addressed envelope to AARS, PO Box 218, Shenandoah, Iowa 51601. It lists all the official display and test gardens throughout the United States.