Growing vegetables | Orange County Master Gardener Volunteers

Watering

Vegetable gardens need at least 1″ of water each week.

Determine when to water by examining the soil rather than the plants. Generally, if the soil is dry when scratched to a depth of 1–2″, watering is necessary. On the other hand, if adequate moisture is available, the next watering can be scheduled for at least 2 days.

Avoid watering the soil often for short periods of time. Shallow waterings promote the development of roots in the top 1–2″ of soil only. This limited root development does not pose any real threat to plant growth early in the season because adequate moisture is generally available and needs for water are low. As the weather gets hotter and moisture is farther away from the soil surface, however, shallow-rooted plants will need water at frequent intervals (every 2–3 days) just to prevent wilting. At this stage in the plant’s life visible evidence indicates that they are suffering from a lack of water.

Sprinklers

If you use a portable lawn sprinkler, keep the application rate low enough that water does not run off the soil and make sure that the plants do not interfere with the application pattern. Often this requires mounting the sprinkler on a small platform above the plants.

Taking evaporating losses into account, a garden needs ~ 75 gals / 100 sq ft to wet the soil to a depth of 6″, i.e. about 1.5–2 hours for average water pressure and hoses to apply 1″ of water to 1000 sq ft.

The best way to check is to dig into the soil to see how far the water has penetrated. A less accurate but easier approach is to measure how long it takes to apply 1″ of water by placing small, straight-sided containers (tuna cans) in a grid pattern over the area being watered. Check the containers every 30 minutes until they contain 1″ of water.

Drip irrigation

A variety of drip and trickle irrigation systems are available through garden centers and mail-order catalogs. A soaker hose is the least expensive and easiest to use. These systems operate at low pressure and deliver small amounts of water to the soil very slowly. A problem that sometimes occurs is clogging of the small holes in the lines if the water comes from a spring. Do some comparison shopping before purchasing a drip system.

Critical water periods

From CMG GardenNotes 716, Water Conservation in the Vegetable Garden

As a rule of thumb, water is most critical during:

seed germination
the first few weeks of development
immediately after transplanting
during flowering and fruit production

Asparagus

Asparagus needs water most critically during spear production and fern (foliage) development. Less water is needed after ferns reach full size.

Cole crops, leafy vegetables

Cole crops (broccoli, cabbage, cauliflower, collards, Brussels sprouts, kale, kohlrabi) and leafy crops (lettuce, spinach, chard, etc.) need consistent moisture during their entire life span. The quality of cole crops is significantly reduced if the plants get dry anytime during the growing season. Water use is highest and most critical during head development.

Beans

Beans have the highest water use of any common garden vegetable. During blossoming and fruit development, beans use ¼″ to over ½″ of water per day. Blossoms drop with inadequate moisture levels and pods fail to fill. On hot, windy days, blossom drop is common. When moisture levels are adequate, the bean plant is a bright, dark, grass-green. As plants experience water stress, leaf color takes on a slight grayish cast. Water is needed at this point to prevent blossom drop.

corn

Water demand peaks during tasseling, silking, and ear development. Water stress delays the silking period, but not tasseling. Under mild water stress, the crop may tassel and shed pollen before silks on ears are ready for pollination. The lack of pollination may result in missing rows of kernels, reduced yields, or even no ear production. Yield is directly related to quantities of water, nitrogen, and spacing.

onion family

These crops require consistent moisture and frequent irrigation due to their small, inefficient root system.

peas

Peas need water most critically during pod filling.

root crops

Crops like carrots and potatoes require consistent moisture. Cracking, knobby, and hot-flavored root crops are symptoms of water stress.

Tomato family, vine crops

The tomato family (tomatoes, peppers, eggplants) and vine crops (cucumbers, squashes, melons) need water most critically during flowering and fruiting. Blossom end rot (a black sunken area on the bottom of the fruit) is often a symptom of too much or too little water. These crops have a lower water requirement than many vegetables and are often over-watered in the typical home garden.

Restricted irrigation

Restrictions that allow for thorough watering only twice a week should not have a major effect on the vegetable garden. With adequate soil organic content, the garden should be able to go 2–7 days between irrigations.

Avoid heavy water use crops such as beans and sweet corn.
Grow only what you need. Consider that one tomato plant can yield over 20 pounds of fruit.

When water restrictions prohibit outdoor watering, do not plant a vegetable garden. Vegetables do not go dormant like a Kentucky bluegrass lawn. If water restrictions allow, consider planting containers with vegetables and non-irrigated or minimally-irrigated cover crops in the vegetable garden area.

Fertilizing

To keep vegetables growing rapidly and continuously, extra fertilizer should be applied as a sidedressing. Sidedress most vegetables about midway through the maturity cycle, except when growing on sandy soil or during periods of excessive rainfall. These conditions require more frequent applications. Sidedress crops with long growth cycles such as tomatoes, eggplant, and okra 2–3 times per season.

Rows

Sidedressing can be applied on both sides of vegetable rows about 4–6″ from the plants. Fertilizer applied by the banding method is placed in furrows 3″ from the sides of the row and slightly below the depth of the seed. Apply only one of the following per 100 feet of row:

1 cup of 33% ammonium nitrate
2 cups of 16% sodium nitrate
3–4 cups of 8-8-8 fertilizer

banding NC CES Home vegetable gardening

Individual plants or hills

Use 1 level tablespoon of ammonium nitrate per plant. For plants that are widely spaced, such as cucumbers or cantaloupe, the sidedressing can be placed in bands 6″ from the plant base.

Weeding

Gardens infested with weeds produce fewer vegetables because the weeds compete for the available soil nutrients, water, air, and sunlight. Weeds also provide a home for insects and diseases. You can control weeds through 3 methods, hoeing, mulching and herbicides:

Hoe

A steel hoe is one of the most effective weapons in fighting the war against weeds. When used properly, it is fairly accurate, very selective, always effective and inexpensive. However, you will not be able to control all weeds with the hoe alone. Weeds at the base of the plant must be pulled by hand. Do not allow weeds to become well established before they are removed because pulling large weeds can damage the root systems of vegetable plants. You can decrease the amount of hoeing you must do by using mulches and herbicides.

Mulch

Mulches help to retain soil moisture and reduce weed growth. They fall into two categories: organic types that decompose naturally in the soil, and inorganic types that do not decompose and therefore must be removed after serving their pupose. The choice of an organic or inorganic mulch depends on the season and what purpose the mulch serves:

Organic mulch

Organic mulches are best if the goal is to conserve moisture and reduce soil temperatures during the summer. They can also help to reduce soil crusting.

Organic mulches are by far the most common — bark chips, compost, ground corncobs, chopped cornstalks, grass clippings, leaves, manure, newspapers, peanut shells, peat moss, pine needles, sawdust, straw, and wood shavings.

Organic mulches are most useful in conserving soil moisture and reducing the soil temperature by 8–10°F during the summer. For this reason they should not be used too early in the spring. If mulches are applied to cold garden soils, the soils will warm up more slowly and plant maturity will be delayed. On the other hand, organic mulches can reduce soil crusting.
After the soil warms in spring, an organic mulch may be applied to a depth of 2–4″ around well established plants. Be sure that there is adequate moisture in the soil before applying the mulch.
Mulches such as sawdust, wood shavings, and corncobs can use up some of the soil nitrogen as they decompose. To compensate, you should add 1–2 cups of 8-8-8 or 10-10-10 fertilizer to each bushel before applying them.
Weeds around the outside of the garden and between rows can be reduced by putting down several layers of newspaper and then covering them with leaves.

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Inorganic mulch

The greatest value of inorganic mulches is their ability to increase soil temperature very early in the growing season when the soil is cool.

These mulches, such as clear or black plastic, are easier to use if applied before planting. Groundcloth is now considered preferable to plastic. Soil moisture should be high before these filmlike materials are placed over the soil. Groundcloth is applied as strips, placing each over the prefertilized row to be planted, then burying the edges to prevent the wind from blowing it away. Short slits are then made in the material with a pocket knife for depositing seeds or planting transplants.

Clear plastic increases soil temperature 8–10°F. The soil warms faster with clear plastic than with any other type of mulch. Because clear plastic does not exclude light, germination of weed as well as crop seeds is stimulated. The plastic must be removed as soon as the seedlings emerge through the soil.
Black plastic increases soil temperature 5–6°F early in the growing season and reduces the weed population. Black plastic is highly recommended for crops that produce fruit on the ground, such as melons, cucumbers, squash, and tomatoes and is preferable to groundcloth.

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Herbicides

There are several disadvantages to herbicide use.

No single herbicide will control weeds in all vegetable crops.
It is difficult to apply relatively small amounts of herbicides evenly on the garden surface. Miscalculation or miscalibration of the application equipment can cause some areas of the garden to be treated with too much or too little of the herbicide, which can lead to growth problems for some vegetables.

Dacthal (DCPA) and Treflan (trifulralin) are the two herbicides labeled for use with the broadest range of vegetables in the home garden. Dacthal may be purchased as a granular and wettable powder. It is generally applied to the soil surface after planting. Treflan may be purchased in granular and liquid forms. Unlike Dacthal, Treflan must be applied to the soil surface and then incorporated into the top 1–2 inches of soil by raking or rototilling.

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