Have you seen any new flowers at the garden centers lately? Maybe the question should be, have you seen anything you recognize at the garden centers?

For the past several years, plant breeders have been working overtime to deliver brand new flowers or new versions of our old favorites. Why? Because new sells.

That's a good thing -- and a bad thing -- for gardeners. It means we have a great selection to choose from each spring. But if you're looking for a specific color of a specific annual that you grew last year, you may be out of luck. Plants are rapidly being replaced.

Take petunias, for example. An all-time favorite, this tough garden annual is grown for its consistent flowers, spicy fragrance and a wide assortment of colors. For decades, we had two basic types of petunias: grandifloras (with large flowers) and multifloras (with small to medium-sized flowers).

Then came the millifloras (dwarf petunias with lots of very small flowers). About 15 years ago, a wilder petunia species was crossed with multiflora petunias, which resulted in a new form -- the trailing petunia.

Today there are five types of Wave petunias alone (the best known of the trailing petunias) from just one plant breeder, Pan American. Several other breeders have similar trailing petunias, with names such as Supertunias, or Surfinias. If you add up all the new crosses of petunias, there could be as many as 20 new introductions a year.

To get a taste of the range of petunias available, we put together a cheat sheet on the types of Wave petunias in garden centers:

WAVE

The original trailing petunia, the Wave is a spreader that hugs the ground. The flowers are formed along long stems that can reach 3 feet. Colors: In addition to the original purple, it comes in pink, lilac and rose.

Spacing: 12-24 inches.

Height: 4-6 inches.

Width: 36-48 inches.

SHOCK WAVE

Shock Wave, the newest Wave form, was introduced this year. Its selling point is that it has more flowers that start to bloom slightly earlier than other Waves. The medium-sized plants are almost totally covered with flowers, which bloom above the foliage. While I don't know if it's the "best petunia money can buy," as its promoters maintain, it did look good in trials in Minnesota.

Colors: Ivory, rose, pink, purple, pink-veined and mixed.

Spacing: 10-15 inches.

Height: 8-10 inches.

Width: 24-36 inches.

DOUBLE WAVE

Double Wave is very similar to Wave, but boasts double flowers. While they're lovely, some gardeners say double petunias don't always look the best. Faded or wet flowers can resemble masses of wet tissue hanging, and the plants don't have as many flowers as single types.

Colors: Blue vein, blue velvet, lavender, pink, purple, rose and white.

Spacing: 12-18 inches.

Height: 4-6 inches.

Width: 18-24 inches.

EASY WAVE

This taller version of the original Wave mounds as well as spreading.

Colors: Blue, pink, rose, red, white and salmon.

Spacing: 10-15 inches.

Height: 6-10 inches.

Width: 24-36 inches.

TIDAL WAVE

The tallest of the Wave petunias, Tidal Wave forms hedgelike plants.

Colors: Silver, cherry, purple, hot pink.

Spacing: 12-24 inches.

Height: 16-22 inches.

Width: 24-48 inches.

GROWING TIPS

Full sun and well-drained soil are best for petunias. Wet soil and standing water can be deadly for them, so water only when the soil is dry. Commercial growers joke that trailing petunias need as much food as a teenage boy. So, in addition to a slow-release fertilizer, supplement with a weekly water-soluble fertilizer.

Mary Hockenberry Meyer is a professor and extension horticulturist with the University of Minnesota.