The best sources of water are rain or from underground sources. However, you will most likely need to supplement between rainfall by watering by hand or through an irrigation system such as drip irrigation.
Home Vegetable Garden Guide
DRIP IRRIGATION Soaker hoses are probably the easiest and most efficient form of garden irrigation. Watering at the root level instead of from the top cuts down on moldy leaf diseases, saves money, reduces the time you spend watering, and produces healthier plants over other forms of irrigation.
Place your soaker hoses no closer than 2" from the base of the plant and about 12 to 18" apart. They will water about 6 to 9" to either side. Timers, connectors and other gadgets are available for these types of hoses to make it even easier.
TRENCHES Simply place a garden hose between the rows and let it run on a slowish trickle for about 15-20 minutes. You will probably have to move the hose to make sure all the plants in the row get watered depending on the length of the row.
HAND SPRAYERS For container and small gardens, hand sprayers are perfectly fine, with some exceptions. A soft steady stream straight to the base of the plant until thoroughly soaked is best. Be careful not to blast the plants with a hard stream and avoid getting the leaves wet to prevent scorching and diseases.
For container vegetable gardens, first be sure the containers you are using have adequate drainage. Spray the base of the plant until water runs out the holes in the bottom of the container.
How often you will need to water your plants depends on several factors to take into consideration. We water our gardens about 2-3 times a week in our hot, humid, and sandy soil conditions. Below are some conditions you will need to take into consideration to correctly approximate your gardens needs.
SOIL Soil type plays a large role in determining how often you will need to water. Soils consisting mostly of clay hold water very well, perhaps a little too well on some occasions. Sandy soils tend to let the water run straight through. Whichever type of soil you have, improving your soil's consistency by adding in compost or organic matter. This will lighten the more dense soils, give the sandy soils more to retain water with and add an overall benefit to the plants health by providing nutrients.
WEATHER Hot, sunny days - especially during the summer months - will require more than usual watering of course. During cool and humid days you should water a little less. Windy conditions also dry up the soil a littler quicker.
PLANT REQUIREMENT Some plants are more tolerant of dryer conditions and some plants will require different watering schedules during its growth cycle and maturity.
SEEDS/SEEDLINGS New seeds need to be treated with care and watered regularly. Use an adjustable spray nozzle attached to a hose or a sprinkler style watering can. This is because the soil and seeds need light watering and in droplets. Watering with too much pressure can disturb the seeds.
Try to water during the cooler parts of the day to prevent evaporation. Watering in the evening is also ok.
If watering in the evening, be sure to keep the leaves and top portion of the plant from getting wet. The reason why watering in the evening isn't as ideal as the morning is because plants that sit through the cool night with water on their leaves are more susceptible to fungal diseases.
If you have plants in containers, you definitely want to water everyday on hot days like this.
If your plant has wilted in the evening, don't panic just yet! Sometimes your plant may be growing quickly, causing the leaves to get ahead of the root system. This can cause the plant to wilt in the afternoon.
As a good rule of thumb, if your plant is wilting in the morning, water immediately! If the plant is wilting during the end of the day, extra water may not be required and may actually shock the plant if you spray cold water onto it when it's hot out.
Its easy to check, just gently dig down around the roots to see if the soil is moist. If it isn't moist, water away!