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.
The best time to water your garden in summer is from 6 am to 10 am—before the heat of the day sets in, giving your plants plenty of time to drink up and any moisture on the leaves to dry off before nightfall. What is this? If watering in the morning isn't possible, the next best time is from 4 pm to 7 pm.
The best time to water outdoor plants is in the morning when temperatures are usually cooler. This gives the plants time to absorb the water so they can get through a long, hot day. The second-best time is late in the afternoon or early in the evening. Try not to water at night.
Watering Plants At Night Isn't Needed: Although the idea has been around for years, most plants don't need extra care by watering them at night. There are a few exceptions, but 99% of your plants, indoors and out should only be watered during the day.
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. The water must go down, down, down to encourage deep roots and get away from the hot soil surface.
The best time to water plants is in the morning or evening.
More importantly, watering at these times actually helps the plant retain water. If you water in the afternoon, especially during summer, the heat and sun are at their peak and the plant's water will evaporate instead of absorbing into the soil and roots.
Most plants shut down during extreme heat, so if it is over 100 degrees, it may be best to wait to water even if your plant is stressed. Throw a damp sheet over it, or mist it lightly to bring the temperature down.
Even in wet seasons, watering usually helps, because the water that falls then isn't all available to plants. Roots need air to function, and a “cats and dogs” rain temporarily drives all the air out of the ground.
If the soil feels dry, it's time to water. In the spring and fall and in cooler climates, it might be sufficient to water container plants every two to three days. In the summer and in warm climates, container plants usually require daily watering, unless they are succulents or other drought-tolerant xeriscape plants.
Wetting leaves.
Plants get their moisture through their roots, not their leaves. Direct watering to the soil surface and avoid wetting leaves because water helps spread some plant diseases. Use a watering wand to reach ground level or a soaker hose or trickle irrigation system to wet the soil rather than the leaves.
Avoid watering when temperatures are below 40°F or when sustained freezing temperatures are expected within 24 hours as this water will freeze and not be available to the plants.
As the weather heats up and plants reach full size, you may need to water containers (and especially hanging baskets) twice a day.
There's no cut-and-dry definition of a deep watering. Most gardeners generally refer to it as when water has soaked at least eight inches into the soil. This gives plants the structure required to survive lack of water, whether from a drought, a busy gardener, or other environmental stresses.
Leaf scorch is caused by failure of the tree to supply enough water to the leaves at a critical time, usually in July and August. A great amount of water evaporates from the leaf surface because of sun and wind during hot, dry weather. If the water supply is deficient, the exposed leaves dry out and scorch.
We should water the roots so that the plant grows healthy.
A common rule of thumb is that plants need the equivalent of 1 inch of rain a week. If your gauge shows that your yard only got half an inch of rain last week, your plants probably didn't get enough moisture.
California drought regulations ban watering for 48 hours after a rain, but Mark Mahady with Walter Andersen Nursery said most homeowners should wait longer than that. "Most established plants will need no water for another week," said Mahady.
Rainy weather is upon us, which makes it a great time to turn off your irrigation system. Watering your plants is not necessary when nature is doing it for you. It's also not necessary for at least two days after it rains, and often for much longer.
So, how hot IS too hot for plants? The general answer is around 90 degrees F, with some exceptions to the rule.
Watering Plants and Lawns Efficiently
DO water early in the morning when sunlight is weakest, the ground is coolest and foliage will have hours to dry before nightfall. Aim for between 5 a.m. and 10 a.m. DON'T water in the evening when soil is warm and wet foliage can attract insects, fungus and disease.
Avoid full sun
In the current hot breezy weather it is probably best to water in the early evening. This gives the plants enough time to dry out, but there is still the chance for overnight water uptake by the roots. And if you want to water in the morning then start very early – before the sun is shining.
Keep in mind that morning sun, which is cooler and less intense, is easier on shade loving plants then the hot afternoon sun. Plants that receive too much intense light will scorch if pushed into too much hot sun.