If your plants are in the ground (versus a pot), the general rule is that plants need one inch of water per week. However, this does NOT mean watering one time per week. That doesn't usually do the job. Plants do best when watered deeply about three times a week, factoring in the rain.
Overwatering, in simple terms, drowns your plant. Healthy soil allows for oxygen to exist in the space between particles of soil. If there is too much water or the soil is constantly wet, there is not enough air pockets. This results in a limited oxygen supply and plants are not able to breathe.
Container Plants
Containers dry out more quickly than garden beds, so it's best to increase watering in the summer. During heatwaves, water container plants twice a day, once in the morning to give plants a boost before the sun begins to bake down, and once in the evening to replenish what the day took away.
One of the most frequently asked questions we get is how much water to use and how frequently do you water the plants. 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.
You cannot overwater with one watering. You could apply a gallon of water to the pot, and the excess would just drain out of the drainage holes. This is a waste of time and water, and can leach out nutrients, but it doesn't hurt the plant as long as the soil drains well.
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.
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.
Provide Slow, Deep Watering
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.
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.
When a plant is first becoming overwatered, leaves turn yellow. If soil doesn't have a chance to dry out before you water again, leaves start to wilt. When overwatering is the problem, wilted leaves are soft and limp. (If too little water is the issue, wilted leaves are dry and crispy.)
Watering in the morning is generally considered the best, both for indoor and outdoor plants. Reality is, watering them at any other time of the day won't necessarily harm them, especially as far as indoor plants are concerned. However, there are things you should consider if you are watering your plant's midday.
Allowing the soil to dry out in between waterings (while not stressing the plant) is really important for preventing disease, mold, and growing stronger and healthier plants. Less frequent but deeper watering is better than frequent shallow waterings (once plants are established).
To reduce the risk of harmful chemicals in your water, allow your tap water to sit out for at least 24 hours before using it to water your plants. This allows the chlorine to dissipate.
Additionally, plants that get more sunlight also need to be watered more frequently. As a general rule, Satch says, "the amount of water to use is always about ¼ to ⅓ the pot's volume of water." And if after all that you're still confused, he has a few parting words of wisdom for you: "When in doubt, feel the soil!"
In general, houseplants' potting soil should be kept moist, but not wet. They normally need watering once or twice a week in the spring and summer, but less in the autumn and winter. However, depending on the type of houseplant, this is not always the case.
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.
Insert a trowel into the soil, then tilt the trowel to check the moisture of garden plants. You can also insert a wooden dowel into the soil to determine the depth of soil moisture. If the dowel comes out clean, the soil is dry. Damp soil will cling to the dowel.
While watering your yard plants with bottled water may be impractical, using bottled spring water for your indoor plants will make a big difference for them. To give your plants the absolute best, rainwater and bottled spring water are your best options. Any water containing sugar or salt will hurt them!
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.
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.
The heat of summer can be a death sentence for your plants, but over watering can as well. The best thing you can do is keep the soil moist by watering when the top 1 inch (tip of your finger) feels dry to the touch and to be aware of the symptoms listed above.