Usually when the first inch (2.5 cm.) or so of soil is dry, it's a good indication that watering is needed. In summer, watering outdoor potted plants is necessary daily (and even twice a day) for most species, especially when temperatures reach over 85 degrees F.
We recommend watering your plants twice daily -- early morning and late afternoon. To be more specific, early morning means 7-10am; and late afternoon means 3-5pm.
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.
Overwatering is one of the more common causes of plant problem. Heavy and poorly drained soils are susceptible to becoming waterlogged. Roots growing in waterlogged soil may die because they cannot absorb the oxygen needed to function normally. The longer the air is cut off, the greater the root damage.
Watering container plants.
Pots absorb heat, which can stress plant roots, and the soil in them dries out much faster than soil in the ground. Container plants generally need to be watered daily. During really hot weather, you may need to even water twice a day, especially smaller containers.
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.
Vegetables and fruits that are developing fruit during a heat spell need regular watering to ensure good production. Vegetables typically require daily watering during summer weather, but may need a second watering when temperatures are extremely high.
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.
Overwatered Plants Symptoms
Some symptoms of overwatering to look for include: Slowed plant growth with yellowing leaves. Plants may also suffer from leaf scorch/burn. Water soaked spots and/or blisters (i.e., Oedema) may be visible on plant stems and leaves.
Most outdoor plants can go without water for about a week. Container plants are the thirstiest. Most need to be watered daily. If you're planning to be away, adding mulch around flower and vegetable beds helps keep moisture in longer — even if it doesn't rain during your absence.
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 spring and summer in Southern California, she suggests drip watering three times a week for 18 minutes, then adjusting from there if the soil is too wet or dry. Don't know how to tell? Stick your finger in the soil. If it's consistently moist 2 inches down, your plants are fine.
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.
Plants can go to a maximum of a week without water, however, some plants can go for even longer periods of time, such as for two weeks or even a month. It would depend on the type of plant and its drought tolerance level.
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.
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.
“If soil is left too wet for too long, it can cause root rot,” Marino says. “That's what we call over watering. On the other hand, if your plant's soil is consistently too dry you're likely under watering. Letting your soil dry out before watering is key for plants to receive the perfect balance of water and oxygen.”
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. There may be times when you cannot schedule watering in the morning. In this case, water the plants in the late evening before bed.
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.
When the air and soil temperatures consistently fall below 40 F, it's time to stop watering. The ground can't absorb water once the top few inches freeze. Continue to water your plants up until this point so they're as well-hydrated as possible going into winter.
The notion that wet leaves on sunny days cause scorch in plants was disproved nearly ten years ago. But there is no doubt that watering in full sun is not water efficient – as much of it will evaporate before entering the soil. In the current hot breezy weather it is probably best to water in the early evening.
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.
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.