There are no precise guidelines as to when to harvest your vegetables, but there are some rules of thumb to guide you. Most vegetables are harvested just before full maturity, for maximum flavor and the most pleasant texture. The following are vegetable harvesting criteria for judging whether your vegetables are ready for picking.
Asparagus: Begin harvesting when spears are 6-8 inches tall and about as think as your small finger. Snap them off at ground level and new spears will continue to grow. Stop harvesting about 4-6 weeks after the initial harvest, to allow the plants to produce foliage and food for themselves.
Beans (Snap): Pick before the you can see the seeds bulging. They should snap easily into two. Check daily. It doesn't take long for beans to go from tender to tough.
Beets: You can harvest and eat the green tops that you thin out of the rows. Beets are really a matter of personal preference when it comes to the right size for harvesting. They are ready any time after you see the beets shoulders protruding at the soil line.
Broccoli: We eat the unopened flower buds of broccoli, so check frequently, especially as the weather warms up, to ensure you don't let the flower heads bloom. Don't expect your home grown broccoli to get to the size of supermarket heads. Harvest when the buds are about the size of a match head.
Brussel Sprouts: The sprouts will mature from the bottom up. You can begin harvesting once the sprouts are at least an inch in diameter. Harvest by twisting off or cutting the sprout from the stem.
Cabbage: The cabbage head will feel solid when gently squeezed. Cabbage needs to be harvested when it reaches maturity or it will continue to grow and split open.
Carrots: Carrots can be hard to judge. The tops of the carrot will show at the soil line and you can gage when the diameter looks right for your variety. If the diameter looks good, chances are the length is fine too. But you will need to pull one to be certain. Carrots can be left in the ground once mature. A light frost is said to improve and sweeten the carrot's flavor.
Cauliflower: As with broccoli, your home grown cauliflower heads will probably never match supermarket size. Harvest when the head looks full and while the curds of the head are still smooth.
Corn: About 3 weeks after the silks form, they will turn dry and brown. The kernels should exude a milky substance when pricked.
Cucumber: Cucumbers race to the harvest with zucchini. Check daily and harvest young. Timing and length will vary with variety. The fruits should be firm smooth. Over ripe cucumbers can be very bitter or pithy, even before they start to turn yellow.
Eggplant: Slightly immature fruits taste best. The fruits should be firm and shiny. Cut rather than pulling from the plant.
Onions: Onions can be dug once the tops have ripened and fallen over. Allow the onions to dry in the sun.
Parsnips: Parsnips taste best if they are left in the ground until after a frost or two. They can be left in the ground over the winter and harvested in the spring. In cold areas, they should be mulched for the winter.
Peas: The pea pods should look and feel full. Peas are sweeter if harvested before fully plumped. Peas really need to be tasted to determine if they are sweet enough.
Potatoes: 'New' potatoes can be harvested when the tops start to flower. Carefully dig at the outer edges of the row. For full size potatoes, wait until the tops of the potato plants dry and turn brown. Start digging from the outside perimeter and move in cautiously to avoid slicing into potatoes.
Pumpkins: Once the pumpkins have turned the expected color and the vines are starting to decline, they can be cut from their vines. Don't leave them out if a hard frost is expected.
Radishes: Radishes mature quickly. You will see the shoulders of the bulbs popping out of the soil line. If left too long, they will become tough and eventually go to seed.
Spinach: Spinach goes to seed quickly. Harvest by cutting at the soil line before you see a flower stalk beginning to shoot up.
Tomatoes: Harvest tomatoes when they are fully colored and slightly soft to the touch. Gently twist and pull from the vine.
Turnips: The turnip shoulders should be about 2 to 2 inches in diameter at the soil line, when ready. Harvest once they reach maturity. Overripe turnips become woody.
Watermelon: The white spot on the bottom of the melon should change to a deep yellow when ripe. Some people can hear a change in the sound made when the melon is thumped with a finger. It should make a hollow sound when ripe, but this is a skill that must be developed.
O My Garden Place to learn more gardening and planting for lovely garden: www.omygarden.net