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Over the Garden Fence: 06/01/2017

Vegetable watering tips

Vegetables are mostly water: an ear of corn is 70 percent water, a potato is 80 percent water, and a tomato is 95 percent water. Vegetables will not grow and yield without consistent, even watering.

To know when your garden needs water, take up a handful of your garden soil and make a fist: if the soil forms a loose, crumbly ball when you open your hand, you do not need to water; if the soil slips through your fingers, it is too dry, and it is time to water. When plants wilt and look droopy in the morning, it is time to water.

The best rule is to keep the soil in your garden evenly moist - not too wet, never dry.

Here are some critical times to water summer vegetables:

o Beans: during pollination, flowering, and pod development. Blossoms may drop and pods may fail to enlarge if watering is inadequate; 1 gallon per week per foot of row (to measure the number of gallons use a drip emitter and timer).

o Cantaloupe: during flowering, fruit set, and fruit development. Keep the soil evenly moist throughout the season; 1 1/2 gallons per plant per week or 18 inches per season.

o Corn: corn requires consistent, even watering; water is critical during silking, tasseling, and ear development. Water when tassels on small cobs begin to shrivel and 10 days before cobs are picked. Water stress can cause tassels to shed pollen before silks on ears are ready for pollination; lack of pollination may result in missing row of kernels and reduced yields.

o Cucumbers: even, consistent watering during bud development, flowering, fruit development; 1 1/2 gallons per plant per week or 25 inches per season.

o Eggplants: even, consistent watering from flowering through harvest; 1 1/2 gallons per plant per week or 18 inches per season.

o Peppers: even, consistent watering from planting to fruit set and enlargement; 1 pint per plant a week when young, increasing to 1 1/2 gallons per plant a week or 18 in per season.

o Squash: even, consistent watering during bud development, flowering, fruit development; 1 1/2 gallons per plant per week or 18 inches per season.

o Tomato: consistent, even watering is critical during flowering, fruit set, and fruit enlargement; 2 1/2 gallons per plant each week or 24 inches per season. More water may be needed for unmulched plants. Older late-maturing varieties may require less water near harvest.

Most vegetables need an inch of water per week. That is about 62 gallons for each 100 square feet; this amount will soak down to about 8 inches in the soil.

The best way to water is to deliver water to the base of the plant: use drip irrigation or small trenches that will allow the water to flow and seep into the ground. Sprinkler and overhead irrigation can result in foliar disease, especially if plants do not thoroughly dry before evening or cool temperatures.

Drip and trickle irrigation systems are the most efficient and can place water very near plant roots. These systems have drip heads that can measure the amount of water delivered to the garden. To measure overhead watering, place four or five small straight-sided containers around the garden while watering; when 1 inch collects in the containers you have delivered an inch of water to the garden.

The amount of water needed will depend on the type of soil in the garden: clay soil will hold more water than sandy soil and require less watering. Soil rich in organic matter is best; it is moisture retentive and well-draining. Vegetables growing in containers require frequent monitoring and may require more frequent watering.

Long drip or trickle irrigation allows water to seep slowly and deeply into the soil and not run off. Watering to a depth of 5 to 6 inches encourages the growth of deep roots. Avoid quick, shallow watering, which encourages shallow root growth. Shallow roots are more susceptible to damage by sun and heat.

Mulch around plants to conserve soil moisture. Add aged compost and organic matter to the soil regularly. This will increase the soil's moisture-holding capacity.

Harvest vegetables when they are young and just ripe. Young vegetables will require less water and will be tenderer and tastier than vegetables that sit in the garden past their peak.

Steve Albert is the author of The Kitchen Garden Grower’s Guide available at He teaches in the landscape design program at the U.C. Berkeley Extension. He lives in Oakmont.


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