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Watering and Water Content of Vegetables

Watering beets1

Watering beetsVegetable crops need 1 inch of water each week–as a general rule of thumb; this is the equivalent of about ½ gallon of water or slightly more per square foot of garden. Some crops need more water, and some need less.

The best vegetable crop production comes from consistent watering. It is important to avoid having vegetable plants go dry-then wet-then dry; this will cause plants to grow in stops and starts. Uneven watering can lead to uneven production and often uneven appearance and size of vegetables. Vegetables that are under-watered and come to harvest with a low water water content can be bitter or tasteless.

The objective of watering vegetables is to replace the moisture lost from transpiration and soil moisture evaporation. The goal is for soil moisture to remain more or less constant–just moist, not wet or dry is optimal. Vegetables generally need the most water during mid- and late-summer and when the weather is particularly hot.

It is time to water your garden when a handful of soil squeezed into a clump falls apart when lightly touched.

One-inch of water each week is the average needed to keep the soil just moist. In arid or particularly hot regions, about 2 inches of water each week is required. The amount of water may vary from ½ inch per week early in the season to more than 1 inch later in the season.

Vegetables that receive too little water (or too much water) will stop growing. When a vegetable begins to wilt from lack of water, it has already stopped growing for a day or more. (Temporary wilting of fruiting crops such as squash and cucumbers on a hot summer afternoon is not necessarily a sign of inadequate watering–this can be a sign of normal photosynthesis at its water-demanding peak.)

As each crop grows toward harvest, it is important to keep the soil evenly moist and allow the crop to attain its optimal water content–this will make for the best form, color, and taste. Under watering can leave vegetables bitter; overwatering can leave vegetables tasteless.

Percentage water content of vegetables:

• 96 percent: cucumber, butterhead lettuce, crisphead lettuce, zucchini.

• 95 percent: celery, witloof chicory, romaine lettuce, radish.

• 94 percent: Chinese cabbage, collards, endive, looseleaf lettuce, rhubarb, scallop squash, summer squash, ripe tomato.

• 93 percent: green cabbage, sweet pepper, Swiss chard, green tomato, watermelon.

• 92 percent: asparagus, beet greens, red cabbage, cauliflower, eggplant, Casba melon, mushroom, bunching onion, pumpkin, spinach, strawberry, turnip root.

• 91 percent: broccoli, savoy cabbage, mustard greens, dry onion, turnip green.

• 90 percent: green beans, honeydew melon, netted melons, okra, rutabaga.

• 89 percent: edible-podded pea, winter squash.

• 88 percent: carrot, parsley, hot pepper, Hubbard squash.

• 87 percent: beet roots.

• 86 percent: Brussels sprouts, butternut squash.

• 85 percent: kale.

• 84 percent: artichoke.

• 83 percent: leek.

• 80 percent: parsnip.

• 79 percent: green pea, potato.

• 77 percent: salsify.

• 76 percent: sweet corn.

• 73 percent: sweet potato.

• 70 percent: lima bean.

• 67 percent: Southern pea.

• 59 percent: garlic.

Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. Harvesttotable.com has more than 10 million visitors each year.

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  1. Wondering how this information translates if using drip system in raised beds. I am challenged to know how often and for how long to water. Also problematic is that the beds are on one system, thus all veggies getting same time. I currently am using a soaker

    • All vegetables should get water to the deepest roots. For most vegetables, the roots are as deep as the above soil part of the plant–that is if the soil is loose and humus-rich. You can use a moisture meter to measure soil moisture or you can use a thin wooden rod to get a rough estimate of how moist the soil is. If you are using a drip system you can choose differing drip heads to deliver more or less water. The best rule of thumb is to keep the soil evenly moist, not wet.

  2. Hello! I am a chemical engineering student writing a report on vegetable processing. I was just wondering- where did you find the information for this article- I would like to take a look at the source! Thanks !

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