Eleven months out of the year, you can cruise along Three-Mile Drive at the Minnesota Landscape Arboretum and never even notice them.

But around Memorial Day, something extraordinary happens.

Flowers burst from several acres of azalea bushes in such a vibrant assault of colors — gold and mandarin and lemon — that they "stop people in their tracks," said horticulturist Stan Hokanson.

It's one of the most popular tourist spots at the arboretum in Chanhassen. Thanks, in large part, to a patient man named Harold Pellett.

Before Pellett arrived at the University of Minnesota, the colorful flowering azaleas were too fragile to survive our winters, much to the dismay of Minnesota gardeners. As the head of a plant breeding program, he made it his mission to change that.

Why mess with Mother Nature? "It's partly plant envy," said Steve McNamara, a landscape scientist who worked with Pellett. "We want what we can't have."

At the U, scientists started crossbreeding species of azaleas in 1958, hoping to produce a hardier offspring. It took 20 years, and generations of hybrids, before Pellett unveiled the winner: a winter-proof azalea called Northern Lights.

Since then, a dozen new varieties, with such names as Golden Lights and Spicy Lights, have sprouted from Pellett's testing grounds and into garden shops throughout Minnesota. Two more — a bright red and a double-flowered azalea — may be ready for prime time next year.

"When you see these in bloom, it's just really a stunning display," said McNamara. "There's really nothing quite like that."