Annual vegetables can be divided into two general categories:
These include lettuce, peas, and most of the cabbage and onion families. They grow best when the weather is cool -- in spring and fall -- and most can take at least a light frost. In much of New York, you usually plant them through the spring for early summer harvests, then again in midsummer for fall harvests. The plants are usually compact, their root systems are relatively small, and they are more sensitive to nutrient deficiencies.
These include tomatoes, peppers, eggplant, beans, corn, and the family of vine crops that includes squash, cucumbers, melons, and pumpkins. Many are tropical plants, and they grow best when the weather is warm. They are often large, sprawling plants with extensive root systems. Those grown from seed need to be planted into warm soil, usually after the last frost date. Those transplanted into the garden (such as tomatoes, peppers, and eggplant) should not be transplanted until after the last frost.
With tomatoes, peppers, and other warm-season crops that need to be started inside, consider purchasing plants from a local garden center or other outlet -- especially if you are relatively new to gardening. Starting your own seed inside and growing vigorous transplants can be a challenge. Plants often fail to thrive inside due to lack of light (even in "sunny" windows) or improper humidity or temperature.
Whether homegrown or purchased, you need to gradually acclimate transplants to the rigors of outdoor life. Move them outside for a few hours each day as transplanting time approaches. Gradually increase their time outside, and decrease their water. When conditions are right for transplanting, remember that calm, overcast days are best for the plant. Transplant late in the day if possible. Immediately water thoroughly, and don't let the soil dry out while the transplants adjust.
If you plant a lot of beans all at once, you'll harvest a lot of beans all at once -- probably more than you or your family can use at the time. To avoid harvest-time surplus and waste, spread out plantings of certain vegetables. If you plant a little bit every week or so, you can harvest crops over an extended period. With some salad crops, such as leaf lettuce, you can harvest in what's called "cut and come again" fashion. Simply cut the leaves off an inch or two above the ground. The plant will regrow (if conditions are right) and provide you with another harvest a few weeks later. See the Vegetable Growing Guides for more information about which plants you should seed in successive plantings.
When the weather gets too warm for cool-season crops, many of them (such as lettuce) "bolt" -- their leaves turn bitter and the plants elongate and start sending up flower stems. Others (such as peas) simply stop flowering and die. When you remove these plants from the garden, you may still be able to plant a warm-season crop (such as beans) in their place, or start another cool-season crop for fall harvest.