If you're of a mind to pick blackberries, keep your eye on the weather and your hand on a cellphone.

Generally, blackberries grown to the south ripen earlier than those grown to the north. The farther north you go, the later the blackberry season starts. Cool weather slows ripening; rain speeds it.

Here's a snapshot of pick-your-own blackberries in Dallas and surrounding counties.

The closest growers such as Gnismer Farms in Dalworthington Gardens and Merry Berry Farm in Balch Springs expect to pick berries this weekend.

At Larken Farms in Ellis County (south of Dallas), blackberry-picking is under way. Blueberry Basket Farm in Henderson County (southeast of Dallas) expects to start picking berries this weekend.

In Parker County (west of Fort Worth) the season is expected to start about May 31 at Hutton Fruit Farm.

Farther north, in Denton County, berries at Duck Creek Blackberry Farm in Sanger are expected to be ripe around June 7-8.

Parker, Kaufman and Van Zandt counties are roughly at the same latitude as Dallas and Tarrant counties. Ellis and Henderson are farther south. Denton, Collin and Hunt are just north or northeast of the Dallas area. Cooke, Grayson and Fannin are along the Red River near Oklahoma, so their start dates will be later than those near Dallas.

After you figure out where you'd like to pick, call to verify crop availability. Many farms also have Web sites where they update harvest information.

Kim Pierce is a Dallas freelance writer.

Pick-your-own farms

•Texas Department of Agriculture (listed by county): www.picktexas.com

•Navigation is more user-friendly at www.pickyourown.org.