During May and June, garden plants will use about one inch of water each week. In July, August, and September, they require about two inches of water per week for best growth. It normally takes this amount of watering per week to maintain production if no rain falls.
During extremely hot weather (daytime temperatures above 90F and nighttime temperatures above 70F), try to water daily or every other day. In a 10x10-foot garden, this would mean giving your plants 8 to 9 gallons of water each day.
During really hot weather, water your vegetables at least two to three times a week. Watering the garden deeply is critical.
A good general guideline when it comes to watering your plants is an inch of H2O per week, either by rain or watering; in arid climates, it is double that. In hot weather, vegetables need even more water, up to about ½ inch per week extra for every 10 degrees that the average temperature is above 60 degrees.
Quick facts. Water your garden so that your plants always have enough moisture. On sandy, well-drained soil, you may need to water twice a week. For soils that hold moisture, such as heavier clay soils, or loamy soils rich in organic matter, watering once a week is fine.
It is ideal to water lawns about one inch of water per week. To determine how long you need to water to get one inch, place a plastic container in your yard and set a timer. On average, it will take 30 minutes to get a half inch of water. So, 20 minutes, three times per week will give a lawn about an inch of water.
Because the top few inches of soil dried out quickly, shallow-rooted vegetables such as cucumbers, spinach, cabbage, celery, corn, onions, leeks, carrots, broccoli, radishes, and Brussels sprouts will need frequent watering in hot weather or soils that are light on humus or compost.
Sufficient moisture is critical to avoid drought stress; however, overwatering promotes disease, leaches nutrients and wastes time and money.
Gardens generally need watering 2 or 3 times a week, but sometimes that might not be possible, especially if you're away. So what happens then? How long can your garden go without water? In general, a vegetable garden can survive up to one week without water before showing signs of significant stress.
Deep soaking two to three times a week—considering rainfall—will promote healthier, more productive growth than frequent shallow watering. The best way to know if your vegetable garden needs water is to stick your finger down into the soil a couple of inches.
In hot weather you need to water in the mornings when it is cooler. This will allow more water to reach the root system before it evaporates in the heat.
When the soil sticks in your hand and you can form it into a ball, it is moist enough. But, if it barely holds together in the palm of your hand, or if the surface looks hard, baked, or cracked, it is probably dry, and it's time to water. See if the soil is dry an inch below the surface; that suggests it needs water.
The general answer is around 90 degrees F, with some exceptions to the rule. This means that when temps rise above 90 and remain there for a lengthy spell: Leaves wilt. Water evaporates into the atmosphere more quickly in high heat, draining a plant's reserves.
And most importantly, plants absorb water more readily when they're not under heat stress—a condition that's more likely to occur when the sun is at its peak. So while it's perfectly okay to water plants while they're in full mid-day sun, it's not the most efficient way to go about it.
If a plant is overwatered, it will likely develop yellow or brown limp, droopy leaves as opposed to dry, crispy leaves (which are a sign of too little water). Wilting leaves combined with wet soil usually mean that root rot has set in and the roots can no longer absorb water.
Irrigate for 20-30 minutes per day during hot weather, allowing water to completely penetrate the soil. When you believe you have watered the garden bed sufficiently, test the soil. Dig some earth from the area close to your vegetable plants, to the depth of the roots.
Beans, corn, squash and cucumbers are the most water-needy vegetables. Tomatoes need plenty of water when they're young, but less water when fruits are ripening.
Drought resistant vegetables are often those with short days to maturity. Other options include the miniature varieties, bell peppers and eggplant for example. They need less water for fruit development than their larger cousins.
Soil that contains a lot of sand doesn't hold water well and dries quickly. Because of this, tomato plants growing in sandy soil may need to be watered more often, about every three or four days. Clay soil, on the other hand, holds water well. Plants growing in clay soil usually only need to be watered once a week.
If you are unsure how long to water new plants, aim for 30-60 seconds for small plants – longer for larger plants while moving the hose to a few locations around the plant. Avoid watering when the soil feels moist. The earth must be allowed to dry out between watering.
The best time to water plants is in the morning or evening.
Morning watering is actually preferable to evening watering as the plant has time to dry before the sun goes down. At night, water tends to rest in the soil, around the roots, and on the foliage, which encourages rot, fungal growth, and insects.