Summer vegetable watering

The question of how much to water or how often to water vegetable gardens is a loaded one. There is no one answer because of variations in soil type, how well the gardener has increased the organic matter through amendment additions, temperature, wind, plant spacing and competition, mulched or not, rooting depth and other factors.

Studies show that gardeners tend to overwater. It’s possible to overwater even with drip systems by letting them run all night instead of an hour or two. The misconception seems to be “it obviously takes a long time to apply enough water because the water drips so slowly.”

Tomatoes, pepper and eggplant have a lower water requirement than many vegetables. Overwatering and underwatering both cause blossom end rot of tomato and pepper fruit. Keep soils medium moist but allow soil to partially dry down between waterings. The most critical time to water is during flowering and fruiting. Blossom drop is sometimes experienced in hot, windy weather, in spite of adequate watering. Avoid the temptation to overwater in these circumstances.

Water stress on corn will delay silking but not tassel development. This causes poor pollination of ears when pollen is shed from tassels before silk appears. The pollination problems from water stress causes poorly filled ears or stunted ear development.

Beans require more frequent irrigation than most other vegetables for optimal production. Beans in the blossom and fruit growth stages use the most water of any vegetable. Depending on temperature and wind, beans may use one-half inch or more of water per day. Blossom drop and reduced bloom indicate that beans have been too dry at some time. Even with adequate soil moisture, hot winds can cause beans to drop their blossoms. Tadpole-shaped beans (plump on one end and skinny at the other) are another symptom of past water stress.

An even-moisture supply throughout growth enhances the flavor of leafy vegetables. Cabbage family crops like broccoli and cauliflower develop strong flavors if allowed to become dry.


Water root crops consistently but note that extra water promotes excess leaf growth at the expense of root development. Excess water applied to root crops following a dry period will cause root cracking. Potatoes become knobby if they become too dry, and may decay in the ground if kept overly wet.

It’s probably obvious that the vegetable garden is no place to try to cut corners with water because moisture lapses decrease the quality of harvested vegetables. Avoid problems by consistent watering. Check soil by inserting a screwdriver or digging with a trowel and checking for a cool, damp feel that indicates moisture. Powdery soil that lacks a cool feel indicates dryness and that it's time to water. Checking the soil also avoids overwatering that decreases quality as well as wasting water.


Photo credits: Peppers, sweet corn, Swiss chard, red beets and carrots - Carl Wilson

The Mean Season is Here

The arrival of ninety degree F temperatures this week is tough on Front Range gardeners used to a cool spring but even tougher on plants. Plants can’t get up and go inside for a cool drink when things heat up!

Plants that grew up in a cool environment aren’t tough enough to take hot, dry conditions. Their cells and structure are simply wimpy. Expect to see some heat stress, leaf scorch, blossom drop and bolting in the garden.

To help plants transition to the heat, water with care. Vegetables like most plants need some soil drying between waterings but don’t let soils dry completely. This is especially critical until leaf tissue toughens. Some vegetables (tomatoes) benefit from more soil drying than others (onions and carrots). Bean blossoms (photo right) drop when short on moisture and pods fail to fill; they require the most moisture of any vegetable.

One note on America’s most popular garden vegetable, the tomato. Fluctuations in water supply, either excessively wet or dry will cause blossom end rot. This could have been triggered in June downpours or by July heat. It begins as a light tan, water-soaked spot on the blossom end of the fruit (photo left). These spots turn brown to black and leathery and there is no correcting it once the damage is done. Future blossoms that set fruit when moisture conditions are better won't be affected by damage to previous fruit. To manage this condition, fertilize and water properly. Use mulch to reduce moisture fluctuations.

Want more specific watering tips? Check Colorado State University Extension's Water Conservation in the Vegetable Garden garden note.

Bean blossom photo credit, Carl Wilson
Blossom end rot photo credit, Colorado State University Extension