Farm fresh; here's where to find picked-the-same-day produce in and around the Bay Area … direct from the grower or at farmers' market

Sunset, Sept, 1987

Contra Costa. Walnut Festival, Walnut Creek, starts at 5 Thursday and Friday, at noon on the weekend, September 17 through 20; $3 adults, $2 ages 6 and under. This year's celebration includes a nutcracking contest, walnut-filled foods, and other eating booths. Call 935-6766.

Marin. Harvest Fair, San Rafael, 9 to 4 September 20; free. Tastings, hayrides, crafts, farmers' market. Call 492-0122.

San Mateo. Art and Pumpkin Festival, Half Moon Bay, 10 to 5 October 17 and 18; free. Join pumpkin pie-eating and pumpkin-carving contests, a Great Pumpkin Parade. Very popular (parking can be difficult). Call 726-3491.

Santa Clara. Santa Clara County Harvest Fair, San Jose, 4 to 9 October 23 and 11 to 6 October 24 and 25; free, parking $3. Much locally grown produce is judged. Nongrowers can also compete in contests from a costumed baby diaper derby to pumpkin carving. Call (408) 295-3050.

Santa Cruz. Brussels Sprouts Festival, Santa Cruz, 11 to 7 October 10 and 11; free. If you're not inclined to celebrate this crop, you can use the little vegetables in a putting contest. Call (408) 423-5590. Apple Annual, Watsonville, noon to 11 September 26 and 10 to 5 September 27; free. Apple Queen Pageant, square dance, parade, bazaar. Most events take place in Callaghan Park, Freedom Boulevard and Sudden Street. Call (408) 724-3849.

Solano. Vacaville Onion Festival, 10 to 6:30 September 5 and 6; $3.50 adults, $1.50 ages under 12. Onion games, onion everything. Call (707) 448-6424.

Sonoma. Sonoma County Harvest Festival, Santa Rosa, noon to 6 Friday and 10 to 6 on the weekend; October 2, 3, and 4; $3 adults, $1 ages 7 to 12, parking $1 to $2. Look at and taste local produce; world championship grape stomp (two partners-a stomper and a filterer-try to beat the rest at filling a jug in 3 minutes). Call (707) 545-4203.

How to recognize perfect produce.

How do you choose perfect farm-fresh produce? Not having been picked green or gassed for shipping, vine-ripened fruits can look quite different from their supermarket counterparts. We asked local growers for advice on selecting some September-harvested Bay Area crops.

Apples

You can find Gravensteins through mid-September. Sebastopol experts say, "For eating fresh, skin color should include a fair amount of red and yellow, but skin surface should be crisp, not waxy. For cooking, any stage is OK, as long as fruit isn't puckery green or wrinkled-aged."

Cantaloupe. "It picks itself; when the melon is ripe, the stem slips off. Look for yellow-orange color, yellow (not green) netting, and a nice scent," says Ray Erickson of Suisun City

Corn. Don't strip corn to check it; exposure to air turns the natural sugars to starch. Ken Dwelley of Brentwood advises, "Silks should look fresh, not matted. Run your hand over the ear to tell if it's filled out at the tip. Make sure there's no drying of the husk. Ask when the corn was picked.

Concord grapes. Roy Vater of Sebastopol says Concords should

be large globes, tight on their bunches, and blackish in color, with a smooth blue "bloom." "And make sure the stems are green-not brown and dried out."