More handy reference info from the Tennessee State University's Institute of Agriculture website and the Eat the Seasons website to help you determine when to buy vegetables. Each vegetable name is followed by it's peak season and what to look for when shopping. And, yes, I know that tomatoes are TECHNICALLY a fruit...
Artichokes: March-May. Heavy, compact, plump globes. Large tightly closed, fleshy leaf scales. Good green color. Heavy for the size.
Asparagus: March-June. Tightly closed buds. Straight, tender, rich green stalks. Open tips and angular or ridged spears are signs of over maturity.
Beets: June-October. Firm, round, smooth, deep red-colored roots. Fresh-looking tops. Avoid those with long roots and rough, scaly areas on surface, because they are tough, fibrous and strong flavored.
Broccoli: October-May. Firm, closed, dark-green florets. Firm, tender stalks. Yellowing green-colored heads of broccoli are over mature.
Brussel Sprouts: October-November. Miniature, compact, bright-green heads.
Cabbage: All year. Well-trimmed, solid heads. Heavy for size.
Carrots: All year. Firm; bright-colored; smooth; clean; well-shaped. Avoid rough, cracked or green-tinged roots.
Cauliflower: September-November. Bright-green leaves enclosing firm, closely packed creamy-white curd or florets. Avoid bruised or open florets.
Celery: All year. Fresh, crisp branches. Light Green to green color. Should not have wilted, rough look or puffy feel to the stalk.
Corn: May-September. Fresh-leaved, green husks. Plump, milky kernels. Avoid cobs with small or large, dented or shrunken kernels
Cucumbers: May-August. Bright, shiny green; firm; well-shaped.
Eggplant: August-September. Firm; heavy; smooth; even dark purple.
Endive: October-May. Firm without bruises. Color should be white with greenish cast. Free of bruises or cuts.
Green Beans: April-October. Crisp, long, straight, blemish-free pods.
Lettuce: All year. Fresh green leaves with no wilted or bruised areas. Heading varieties of lettuce should be medium weight for size.
Lima Beans: April-August. Bright color for the variety. Crisp, dark green, well-filled pods.
Mushrooms: November-April. Dry, firm caps and stems. Small brown spots or open caps are still good in flavor.
Okra: May-September. Tender, bright-green, bruise-free pods, less than 4 1/2 inches long. Pale, faded, hard pods are tough and fibrous.
Onions: All year. Well-shaped; hard; small necks. Dry, papery skins. Free of green spots or green-depressed leathery areas. Crisp green tops. Two- to 3-inch bleached white roots.
Parsnips: October-April. Small to medium size; smooth-skinned; firm. Decay and bruise free.
Peas: April-July. Well-filled; bright green. Swollen, light colored or gray-flecked pods contain tough, starchy peas.
Peppers: All year. Good shape; firm exterior; thick flesh and bright, glossy skin.
Potatoes: All year. Fairly smooth; well-shaped; firm. Free of most blemishes. Avoid bruised, sprouting, shriveled or green-tinged.
Radishes: May-July. Medium-sized (3/4- to 1-inch diameter); good red color; plump; round; firm; crisp. Bright-green tops.
Scallions and Green Onions: March-July
Spinach: March-May. Large, bright, blemish-free leaves with good green color. Yellowing indicates the start of decay. Avoid leaves with coarse stems.
Summer Squash: June-August. Bright color; smooth, glossy skin. Heavy for the size; firm; well-shaped.
Sweet Potatoes: September-December. Thick, chunky, medium-sized with no bruises or decay. Should taper at the end.
Tomatoes: May-August. Well-formed; blemish-free; plump. Over all rich red color and slight softness.
Turnips and Rutabagas: September-March. Small to medium size; smooth; firm; heavy. Few leaf scars at top and few fibrous roots at base. Purple-tinged white ones are turnips. Yellow-skinned, larger roots are rutabagas.
Wax Beans: April-October. Crisp, long, straight, blemish-free pods.
Winter Squash: September-November. Heavy for the size. Hard, good colored, unblemished rind.