Water is essential to the optimum growth of vegetables; the water content of most vegetables is nearly 90 percent. Providing the right amount of moisture to the vegetable garden is as important as supplying the right amount of plant food.
When to water seeds, seedlings, and established plants
• Seeds. Water to the age of your crops: seeds require water to germinate, water gently and lightly after sowing seed to enable sprouting. Water carefully at first to avoid washing away seeds just below the soil surface.
• Seedlings. Seedlings have undeveloped, shallow root systems; water seedlings lightly and frequently to help roots develop.
• Transplants. Transplants should be watered every day until they establish root systems. Regular watering will help roots recover from transplant shock. Give transplants a cupful of water each day. Water around each plant rather than watering the entire garden bed.
• Established plants. Roots follow soil moisture deep. Water to a depth of 6 inches then allows the soil to almost dry out before watering thoroughly again. Use a trowel to dig down just away from plant drip lines to see how much moisture is below the surface. You will soon get a feel for how much to water.
Water-saving tips for the garden
• Finger test. Your finger is a good indicator of how well watered your vegetables are. Stick your finger down 3 to 4 inches into the soil just a few inches away from your crop. If your finger comes away dry, it’s time to water; if your finger comes away glistening wet, let the soil dry out; if your finger comes away just moist with a few flecks of damp soil–your watering is just right.
• Soil. Organic matter will increase your soil’s water holding capacity (by as much as six times), conserve moisture, and reduce evaporation. Add one inch of aged compost to your planting beds twice a year. Work the compost into the soil before planting or add it as a top dressing or mulch during the growing season. Organic matter improves the soil structure. Organic mulches conserve moisture by reducing evaporation and also discourage weeds.
• Watering time. Water when plants need it. If crops are droopy in the morning, it’s probably time to water. Give plants a soaking before the day is too old. Avoid watering at midday or in the late afternoon when water will be quickly lost to evaporation. Where the summer is dry and hot, water at night when evaporation is lowest
• Wilting. Wilting can be is an indicator that plants need water, but can also be misleading. Some plants like tomatoes, peppers, and eggplant tend to wilt slightly during the heat of the day in warm climates, even if the soil has enough moisture. Check soil moisture to avoid overwatering. If plants are wilted in the morning, water.
• Over-watering. Overwatering can be just as harmful to plants as under-watering. Too much water can create an artificial water dependency and result in too much leafy growth. Overwatering can displace soil air that plant roots need to breathe–plant roots can die from lack of air. Excessive watering can uproot plants and wash away nutrients in the soil.
• Cultivation. Lightly cultivate the soil before watering. This will allow water to soak into the soil rather than runoff. Rain, overhead irrigation, and hot baking weather can cause topsoil to form a crust. Break up the crust to capture rain and irrigation.
• Basins and furrows. Form earthen basins around large, deep-rooted plants such as tomatoes, peppers, and eggplants. A basin will help retain irrigation and rainwater. Use furrows alongside row crops to regulate the water that goes to particular plants. Use temporary damns along furrows to concentrate water delivery to plants in need.
• Mulch. Mulch around crops to slow evaporation and choke out weeds competing with vegetables for water and nutrients. Dry grass clippings, leaves, pine needles, straw, and almost any organic matter are good mulches. Be sure your mulch is free of weed seeds. Mulch after the soil has warmed in late spring and after you have given the garden its first good soaking.
• Harvest. Harvest vegetables and herbs as soon as they reach maturity. Crops taste best at the peak of ripeness. Watering vegetables that are past ripe and in decline is a waste.
Watering times for specific crop families
• Bean family. Legumes–beans and peas–need little water until they begin flowering. Water as soon they begin to wilt. Too much water can result in lush leafy growth and a lack of flowering. Water twice a week at flowering time and then again as the pods are swelling. Stringiness in beans can be the result of insufficient moisture.
• Cabbage family. Brussels sprouts, cabbages, broccoli, and cauliflower do best when watered regularly. Give these crops a good soaking ten to twenty days before harvest.
• Corn. Corn needs heavy watering at the tasseling stage and again when the kernels are swelling.
• Fruiting crops. Fruiting crops–beans, squash, melons, cucumbers, tomatoes, peppers–require frequent watering during flowering and fruit formation. These crops are deep-rooted, however, and once the fruit has formed and begun to develop deep and less frequent watering will be sufficient.
• Leafy crops. Leafy crops are shallow-rooted and will do best with frequent light watering.
• Lettuce and greens. Lettuce spinach and other leafy crops need frequent watering but only in the top 6 inches of soil. Leafy crops shallow rooted. Lettuce is less bitter and spinach is slower to bolt if watered regularly.
• Onions. Members of the onion family need frequent, even watering during the early stages of growth to promote good leaf development. Continue even watering as bulbs begin to form. Once bulbs start forming onions and garlic need much less water. For less pungent onions keep them moderately moist. Stop watering when tops begin to brown and dry or ripening may be delayed.
• Potatoes. Potatoes need little water until they start to develop tubers. When tubers are marble-sized give the plants a good soaking and mulch to conserve moisture.
• Root crops. Root crops such as carrots and turnips need even moisture when young and as roots begin to develop. If the soil is allowed to get too dry, carrot roots may split and turnip centers may turn brown.
• Squash and cucumbers. Squashes, zucchini, and cucumbers need an even supply of water from flowering through fruiting. Even watering will enhance fruit development and flavor. Avoid overhead watering when these plants are flowering; pollination may be adversely affected.