How Often Should I Water My Plants?
I’m probably asked this 10 times a day in the summer. Unfortunately, there is no one correct answer. Obviously, we all need to conserve every possible drop of water we can, so responsible irrigation is critical. That begins with selection of plants that are well-adapted to your area and that are known to be water-efficient. It doesn’t mean only cacti and yuccas. It just means you should avoid plants that wilt freely under your Texas conditions.
That said, here are some guidelines.
• Learn to recognize drought symptoms, and watch for them daily. Just because a plant is wilted at 3 p.m. doesn’t mean that it’s dry. Some plants, when exposed to sun, struggle in mid-afternoon. Check the soil to be sure it’s beginning to dry.
• If only a small area or a handful of plants is dry, use the water hose to irrigate that space. There’s no point in running the sprinkler system for the entire lawn and landscape if only one area is dry.
• Encourage deeper root growth by soaking the soil, then letting it become dry an inch or two down before you water again.
• Use mulches to reduce the rate at which water evaporates from the soil’s surface. Mulches also reduce weed growth, further reducing water consumption.
• Adjust your sprinkler timer so that each station will need to be watered at approximately the same intervals. That may mean running one shady station with spray heads for only 10 minutes while a large turf area with impact heads is watered for 30 or 40 minutes. Your goal is to apply about 1 inch per week, but to do so in a way that the water won’t run off.
• "Smart" controllers take a lot of the guesswork out of irrigation. They monitor the weather, and they balance that with the types of plants you’re growing, the soils and slopes, sun or shade – all the environmental factors. These controllers save tons of water – and money!
Now, to the answer you were expecting. Sort of.
• If it’s 90 degrees, you should be able to go a week between irrigations (assuming no rain).
• If it’s 95 degrees, the interval probably shortens to five days if you’re watering correctly.
• At 100 degrees, you’ll probably need to water every four days.
• At 105, the interval shrinks to three days.
Potted plants don’t use the same formulas. They’ll need water more often than their in-ground counterparts.
New trees and shrubs should be hand-watered halfway between sprinkler irrigations to be sure they don’t dry out.
Turf that is less than one month old should be watered lightly once or twice daily for the first two weeks, then every day or two for two more weeks, then as needed forever.