Swimsuit season is all but here, but there’s still time to put your plants on a diet.
Plants use sunlight, CO2, and water* to make food, a process called photosynthesis. As plants make food for themselves, they also make our homes more pleasant for us by releasing oxygen and water into the air through pores in the leaves called stomata. *Plants also use minerals absorbed by the water through the soil.
When stomata open to take in CO2 or release oxygen, water inside the leaves immediately evaporates due to the heat from the rays of sunlight. That’s why it feels much cooler around plants!
As water evaporates, it actually helps to pull the remaining water molecules up. This is key to the process of transpiration, which carries water up against gravity from the roots to the backs of leaves in a plant, even the highest leaf on a tall Palo Verde.
In the summer, this process is more costly for plants as they lose more water when attempting to make food in triple-digit weather. So our instinct to up the water for plants as we do for ourselves is not wrong, but for plants we’re also upping the “calories.”
Too much water actually tells plants to grow at a time when they should be conserving their resources, and it can flood the roots, leading to oxygen starvation. When plants grow too fast in response to both increased water and fertilizers, it also means more work for us to maintain the plants.
So, how much water do plants actually need? The 1-2-3 Rule from Landscape Watering by the Numbers provides an easy system (pictured below) for figuring out how deeply to water depending on the size of the plant. Use a long screwdriver, a piece of rebar, or a soil probe to check you’re watering deep enough.
How often do plants need to be watered? It depends on if they are desert-adapted or not. Desert plants have survival traits designed to help them reduce the amount of water they lose to transpiration. From smaller, thicker leaves to root adaptations, desert adapted plants need less frequent watering than the high water use plants in your landscape.
Desert or adapted or not, when plants are provided supplemental watering, the 1-2-3 Rule helps makes sure that your water is getting deep enough to reach your plant’s active roots.
Once you figure out how deeply to water and how long to time your irrigation system based on the plants in your yard, make sure to change your irrigation frequency at least seasonally. May is the perfect time to adjust your irrigation frequency!
Learn to control the water, and your plants will be healthier for it! Learn more about landscape watering and how to program your irrigation timer.
Check out our event calendar to find our FREE landscape watering classes offered each fall and spring.
Tina Sleeper is a water conservation coordinator with the City of Tempe, one of 20 Water – Use It Wisely partners to offer water saving advice and programs.