The majority of vegetables need well-drained soil to grow. Wet soil is the opposite of well-drained soil and is also referred to as clay soil. If you have wet, or clay, soil, you risk losing many of your plants, even trees, to fungal diseases and rotted roots. You can improve and outsmart a wet, heavy soil by adding organic plant materials, building raised beds, and growing your prized vegetables in containers or raised planter boxes.
Determine if your soil is heavy clay that retains water. In early spring, use your garden spade to dig down about 6 inches in the area where you want to grow vegetables. Gather one handful of the soil and squeeze it in your hand--if it forms and stays in a compressed ball, you have wet clay soil. Wait until later in the spring when your soil has dried out a bit before you begin to improve it.
Dig in organic materials such as any type of compost, peat moss, straw, sawdust, well-rotted manure, wood chips, sand and vermiculite or perlite. Don't skimp on these materials--they can comprise up to half of the volume of your wet clay soil. After you add these materials, rake the top of your bed level.
Build raised beds on top of your wet clay soil. You can build simple frames without bottoms and fill them with sandy, loamy soil that you have purchased. Add the same types of organic materials you would add to clay soil: compost, peat moss, straw, sawdust, well-rotted manure, wood chips, sand and vermiculite, or perlite. Use 2-by 12-inch redwood boards to make frames. You also can use cinder blocks for your raised garden frame. A good size for a raised bed of this type is 3 or 4 feet wide by 8 feet long.
Plant your vegetables in large containers, such as half wine barrels. Make sure your container has at least one drainage hole and then fill it with an all-purpose potting soil. If you want to add nutrients such as compost to your potting soil, they will help to nourish your plants all summer and will reduce the plants' need for additional fertilizer.
Plant a cover crop in fall. Rye, ryegrass, fava beans and winter barley are good choices for a winter crop that you will plow under the following spring.