If your mouth is already watering for that first Vidalia onion of the season, you're in luck. The early spring weather has this year's harvest weeks ahead of the normal schedule.

"Growers will probably start digging onions by the end of March," said George Boyhan, a horticulturist with the University of Georgia Extension Service.

If that's true, he said, Vidalia onions should show up in stores in the first week of April. In more normal years, growers don't start harvesting until mid- to late April.

Early onions aren't the whole story, either. Heading into the harvest, virtually everything about Vidalia onions was sweet.

"The quality is really going to be there, and the yields are going to be there," Boyhan said. "The next hurdle for the growers is the price."

If prices are a little lower this year, though, not many shoppers will complain.

When growers dig their onions, workers cut off the stems and bag them in the fields. On most farms, the onions then go into drying hoppers for two to three days. Then they're packaged and shipped out. An onion dug today may be on a grocery shelf next week.

There's only one little problem with buying the first Vidalia onions of the season.

"In general, sweet onions don't store very well," Boyhan said. "And the earliest onions on the market aren't going to store as well as the rest."

All that means, though, is that you shouldn't buy all your Vidalia onions early. Just buy a supply for a week or so at a time.

Growers plant different varieties of Vidalia onions, he said. Some of those grow faster and develop bulbs sooner than others. One, "Sugar Queen," is particularly early. Growers have about 500 acres of Sugar Queen onions.

"Those are the ones they'll be picking when they first start digging," he said.

The early varieties often have a little flatter bulb than later onions. Because they grow faster, they have a little more moisture in them, too. So they're slightly softer.

"We recommend harvesting onions when 20 percent of the tops fall over," Boyhan said. "With these early varieties, to get the best quality, growers need to wait a little longer and let the onions mature a little more."

But growers plant those varieties so they can catch the all-important early-season market, when prices are high. So instead of letting them mature longer, they normally don't wait as long to start digging as they do for later onions.

As a result, the first Vidalia onions on the market won't keep very long. But there's nothing wrong with the taste. In fact, Boyhan said the early onions are among the sweetest of the season.

"As a rule, the early and midseason onions are the sweetest," he said. "The onions harvested at the very end of the season may be a little hotter."

Whenever you buy them, pay attention to how you store Vidalia onions, Boyhan said. They keep their quality best when kept separate at room temperature, with good air circulation around them.

Refrigerating them may keep them longer but will also make them hotter over time.

By law, Vidalia onions are grown only in a 20-county area surrounding their namesake city. About 200 growers will harvest a crop officially estimated at 14,575 acres.

Boyhan said a number of environmental factors affect onions' pungency. A key one is the amount of sulfur in the soil.

Growers have to apply fertilizer that contains sulfur soon after transplanting their onions. But as the onions develop, rainfall and irrigation tend to leach the sulfur from the naturally low-sulfur, sandy soils in the Vidalia growing area.

"That's one of the reasons they're as sweet as they are," Boyhan said.