Vegetable Garden Watering Requirements

Root Depth

• Water shallow-rooted plants, such as lettuce, beets and chard, until the soil is wet 6 inches below the surface. Water deep-rooted plants, such as corn, tomatoes and asparagus until the soil is wet 2 feet below the soil surface. Water the plants again when the soil is dry 2 inches below the soil surface.

Phase

• Adjust your vegetable watering schedule according to the phase of plant development and the type of plant. Keep germinating seedlings uniformly moist, but not soggy. Developing plants respond better to thorough, deep irrigation every five to seven days than they do to more frequent, brief watering sessions. Critical watering periods for plant and fruit development vary by plant, but most require consistent moisture levels during flowering and fruit development. Beans require consistently moist soil during pollination and pod development. Crucifers, such as broccoli and cauliflower, require at least 2 inches of water weekly during head development. Water onions, carrots, turnips and potatoes once weekly until the soil is wet 18 inches below the surface when the roots are enlarging.

Irrigation

• Irrigation methods include hand watering, drip or trickle irrigation, and oscillating sprinklers. Hand watering methods, such as with a watering can, is adequate in small gardens. Hand-watering methods are inexpensive but require more time than other methods. Drip or trickle irrigation efficiently directs water to the plant root zone at a rate the soil absorbs without runoff. The disadvantages of drip irrigation include the cost and time of setup. Evaporation claims much of the water emitted from oscillating sprinklers. They are the least efficient method of irrigation. Sprinklers are useful when watering large, uniform crops, such as corn.

Mulch

• Mulch reduces soil temperature and evaporation in the vegetable garden. It also reduces weeds that compete with plants for water. Organic mulches, such as straw, leaves and grass clippings, improve the soil's moisture-holding capacity as they decompose. Apply 2 inches of sawdust or grass clippings and up to 6 inches of straw in the late spring after the soil warms. Inorganic mulches, such as black plastic, newspaper and landscape fabric, retain their structure longer than organic mulches. Newspaper is equally effective as plastic mulch and retains less heat in hot climates.

Visual Cues

• Conserve water by observing your plants and soil to determine when they need moisture. Leaves turn bluish green, wilt and fold inward in the hot part of the day if plants need water. Leaves turn a yellowish green, droop and flatten when the plants are over watered. If puddles remain on the soil surface 15 minutes after the plants are watered, add compost to improve drainage.