Posted by Sunset, August 11, 2009 in Sustainable gardening
By Jim McCausland, Sunset Magazine
Today my garden is getting its first significant rain since late June. About 1/4 inch is predicted. Everything is already wet and the raindrops are beading up on the lady's mantle.
It seems to be just what we needed. But is it enough? Let’s do the math.
In good garden loam, an inch of water penetrates 8 inches (in sandy soil, it’s 12 inches; in clay, 4 inches). That means the quarter inch of rain we’re supposed to get today would moisten the top 2 inches of soil in my garden, not reaching most feeder roots on most plants. Not very helpful.
Cass Turnbull, founder of Seattle-based PlantAmnesty, sees the same problem on a regional scale, and has responded by firing off the following witty, insightful open letter to Northwest gardeners. Its principles apply everywhere.
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'Drought tolerant' is not the same as 'drought proof' and many plants (shrubs, trees, and even lawns) around here will die if they don't get some water soon.
Dare I say, "It's a perfect storm"?
People—the thrifty, the ecologically pure, and the tired—will all let 'low water' turn into a 'no-water' situation. Nothing can live without water! And when the plants die (it's called 'permanent wilt' by extension agents), then the shrubs, lawns, and trees will need to be replaced. And that will cost way more money, effort, and CO2.
Summer rains don't count in relieving drought-stressed plants. In fact, they may do more harm than good by creating the illusion that watering has occurred.
If you—or more likely your spouse, friend, or neighbor—don't believe me, go outside after a summer shower (or 'sprinkle' as they like to call them now) and scratch up some dirt. You'll quickly see that only the top 1/16" inch veneer of soil is wet. Under that, it is still dry as a bone! Poor plants!
The lesson is to keep the soil moist enough throughout the summer so that it absorbs water like a wet sponge, rather than repelling it like a dry sponge.
And remember that soils that are rich in organic material and those covered in mulch stay moist longer. In a drought situation this is a BIG DEAL. But I bet you already know that.
THE ONLY RELIABLE way to tell if you need to water is to BEND OVER AND STICK YOUR FINGER IN THE GROUND. Why do so many people not do this? Instead they just guess, and they often guess wrong.
Please soak, soak, soak your plants at least once a month. I use the 'flood' system. I turn my hose on to a slow drip and let it run a long, long time (1/2 hr to all night long) breaking the surface tension, and going deep. Big trees, and especially old Western Red Cedars can slowly die over the next several years, disappearing as the needles drop. Tree roots are mainly in the top 3 feet of soil, most of the 'fine absorbing' roots are in the top inches, and they extend way beyond the drip line, in your lawn, under your patio and even into the street!
By the time the average homeowner notices that the rhodies are all brown, it's too late. A happy rhody's topmost set of leaves stand straight up. An okay rhody has topmost leaves that are horizontal. A rhododendron in big trouble has leaves that hang straight down. Can't you hear them screaming?
If your water will not penetrate the soil, but just rolls off the surface, you may want to use a 'wetting agent.' The product I use is called 'Percolate.' I get it a Sky Nursery. I believe it is a kind of soap that breaks the surface tension 'making water wetter.' I wish they sold it without fertilizer included.
And tell your neighbors!
PlantAmnesty sells 'doorknob hangers' that you can hang on suffering street trees. The hanger says "water me please" and has a nice graphic.
Call or e-mail PlantAmnesty to get some. And make a note to mulch AFTER the soil gets wet, maybe after many long rains this winter to lock the moisture in, not out.
Cass
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