By Jim McCausland, Sunset senior garden writer
In the mild part of the Pacific Northwest where I garden, lawns and most non-native plants usually need about an inch of water per week to thrive. But from May through September, Seattle-area rainfall averages just 1 to 2 inches per month. So unless you have a drought-tolerant garden, plants will go dormant (lawns), die back, or die completely if you don’t supplement occasional summer showers with serious irrigation.
Whenever it rains, it’s easy to just skip that week’s watering. But it’s smarter to measure each week’s rainfall with a gauge that measures precipitation in hundredth’s of an inch, then subtract that from the amount of water you apply. Very often you’ll find that several hours worth of drizzle only amount to one or two tenths of an inch, and though your plants have wet leaves, most of their roots are on the dry side.
To check rainfall, I use a type of gauge that’s been around for more than a century. You can buy one like it (and only part of the gauge is pictured here) for about $30 from The Rain Gauge Store. To check the amount of water sprinklers put down, I use another very old tool: the empty tuna can. It holds just over an inch of water.
When you water, apply it slowly. If it starts to run off before you've put down an inch, turn the sprinklers off and let it soak in before you continue.
