A few weeks back, Don and Bobbie Shepard were among the very few people in town actually looking forward to the arrival of April 15. And why not? As owners of a mom-and-pop iris farm in northwest Phoenix, their business was blooming and, furthermore, their stalk portfolio had never looked healthier.

That mid-April date marked the peak of the monthlong iris season, when the couple's Edenesque lawn explodes into the floral equivalent of Crayola 72, a horticultural fantasia attracting swarms of bees and humans.

Don't make the mistake of underestimating this flower's power. As the Shepards know only too well, the iris is a captivating plant capable of changing entire lives.

Spread over two and a half acres surrounding the couple's ranch-style home at 3342 West Orangewood, the gardens provide a lush showcase for the showy flower Don Shepard calls the poor man's orchid." The state's largest iris-breeding operation, the 21-year-old Shepard Iris Garden currently plays host to 50,000 plants representing about 1,000 different varieties. The blooming season begins in March and extends through April, the same period the garden is open to the public. During the season, there's a steady flow of people in and out all the time," says Shepard, a construction supervisor by day. This month we've had a thousand people a day over the weekends."

Color Shepard's visitors beatific. Catalogues in hand, a half-dozen flower children of all ages wander through the gardens one recent weekend afternoon. Temporarily at one with nature, they frequently stop to smell the iris, jot a note about a particularly enticing bloom or just zone out in the tranquillity of it all. Somehow it's not surprising to learn that an inviting patio that's available for free use by garden-club luncheons has already been booked solid for next year's blooming season.

Don and Bobbie Shepard inadvertently entered the iris sweepstakes 25 years ago, when a neighbor at a previous home gave the couple a pair of tall, bearded plants. We threw 'em out in our vegetable garden, just like anybody else would," Don recalls. At that particular time, we didn't know a single thing about irises."

When the plants finally erupted in a riot of hues two years later, Don and Bobbie wised up fast. That first year, we just enjoyed the colors we had," reports Don. The next year, we knew we wanted more."

And three years later, by which time the backyard garden of their midtown Phoenix home was beginning to look like a set from the botanical sci-fi flick The Day of the Triffids, the Shepards had grown so enamored of the flower that the family was forced to pull up its own roots.

After the Shepards moved to their present, much larger lot in 1971, their full-time hobby really blossomed.

We opened the garden to show people that irises really could be grown out in the hot sun," says Bobbie Shepard, who thought they'd be lucky just drumming up a few new members for a fledgling iris club. Whenever we told anyone we raised irises, people always wanted to know where the greenhouses were."

Amazed to discover that the Valley actually boasts one of the most iris-friendly climates in the country, visitors lined up to buy rhizomes (the bulblike root tubers from which the plants grow) of their own. Today, the budding iris fancier can expect to pay anywhere from a few dollars for a common, garden-variety rhizome to $35 for a newly developed hybrid featuring unusual coloring or flounces.

Why the wide price range? Don Shepard, who spent nearly ten years developing the lavender and yellow Big Duke" (a floral tribute to John Wayne), chalks it up to the laws of supply and demand. From the time you pollinate the flower to the time you introduce it on the market, you've invested a lot of time," he says. It's like a brand-new car-you're going to pay more for it. Of course, as the availability increases, the price drops."

Look for the price to go through the roof should anyone succeed in hybridizing an all-red iris, to date nothing but a botanical pipe dream.

The person that does that will be rich," says Shepard, who's keeping mum about his own hybridization goals. However, he admits it's a challenge giving birth to new, prize-winning irises-like his Chris-Town Jubilee," a cream and apricot strain named in honor of a shopping-mall flower show. It's sort of like breeding horses," says Shepard, who continues his quest for better bloom stock, bud count and blossom color in a hybrid seedling garden at the back of his property. You've got to learn the bloodline of the plants, and even when you do, things still don't turn out the way you think they will. Out of a thousand seedlings, you're lucky if you get one plant that's true to color. It really is a lot of work."

Not that he minds. After all, no one ever promised him a rose garden.