People constantly ask me how much and how often to water their plants. There is no definitive answer. It depends on your microclimate, the type of soil in your garden, the type of irrigation you use (drip, overhead, etc.) and more.
That said, figuring out how to water your plants isn’t all that difficult if you use my “Canary Test.”
In the old days, miners took canaries with them into coalmines. Since canaries are very sensitive to lethal but odorless carbon monoxide gas, the miners knew to leave the mines when the canaries started to get sick.
My “Canary Test” is way to test how often and for how long each of your garden’s watering zones actually needs run. In your garden, the “canary” is the first plant to show signs of water stress.
The Canary Test
Test one watering zone at a time (a watering zone is a set of sprinklers or drip emitters that are connected to the same valve and run at the same time).
Figure Out How Often to Water
- Pick a zone. Make sure you know which plants that zone waters
- Turn the zone off. Mark the date on your calendar
- Wait and watch for the canary - the first plant to show signs of water stress. When you notice a plant whose leaves look a bit wilted, you’ve found your canary. It might take several days or it might take several weeks. Eventually, you’ll see the canary.
- Check your calendar to see how many days passed since you turned that zone off. Make a note of it.
- Figure out how often to water. If, for example, it took 14 days until you noticed a canary in a particular zone, then water that zone every 12th or 13th day (that’s two weeks, minus one or two days). If it took seven days, then water every sixth day, and so on.
Your goal isn’t to get your plants to wilt, but rather to to avoid watering before plants need the water.
Figure Out how Long to Water
- Once you identify your canary, run the irrigation in that zone. Check the soil every five or ten minutes for overhead sprinklers, every 10 to 20 minutes for rotating nozzle sprinklers, and every 30 minutes for drip irrigation.
- Note how long it takes for water to soak deep enough that when you stick your finger all the way into the soil, it is saturated not just at the surface but as deep as you can feel.
If the soil is really hard, you may need to dig down with a hand trowel or soil probe rather than using your finger.
- Repeat the process for each watering zone.
The point is to get water to plant roots deep in the soil. However long that takes is the amount of time to irrigate that zone.
You’ll soon realize that each zone needs to run on its own schedule. Your lawn, for example, may need to run ten minutes, three times a week in summer, but your flower border can go for a week between waterings. Your shrub border can go two weeks or a month, especially if you deep-water each time.
Areas irrigated with overhead spray need to run for only minutes at a time, but drip irrigated areas run for an hour or longer since they release water very slowly.
Repeat the Canary Test for each zone, once a month to create a year-round watering schedule. Winter’s rainfall may provide enough water for weeks or months. On the other hand, in the dry heat of summer, plants need watering far more frequently.
Every time you water, water deeply and thoroughly. Don’t be afraid to use your finger as a probe to test how wet the soil is.
Whether you control your sprinklers manually or use an irrigation clock, adjusting your watering schedule to match your plants’ needs saves tremendous amounts of water and grows healthier plants.