If you’re having trouble staying on top of irrigation this year and driving up your water bill, you’re not alone. Metro Detroit is behind on rainfall for the past month and the heat means that the rain we’ve received hasn’t helped much. Luckily there’s plenty the gardener can do to make the water she uses go farther, while also doing so in a manner that is best for specific crops.
Most plants need about an inch of rain per week, although this increases during hot periods. Having a rain-gauge can be useful because there are extreme local variations in rain-fall. Gardeners can maximize rainfall by adding organic matter to their soil in the form of peat, compost or manure, all of which hold onto more water than topsoil. Mulch also helps keep moisture in the soil as well as gradually adding organic matter. It should come in the form of pine needles, bark or wood chips for perennial beds or straw or leaves for vegetable gardens. Rain barrels can also help you make the most of the rain, although gardeners often exhaust a fifty-gallon rain drum rather quickly.
When you water is also important and by far the best time to irrigate–for conservation’s sake–is in the early morning. This is the coolest time of day and water will move through soil better before the sun is too high. Watering in the evening is discouraged because moisture that lingers overnight can cause disease problems. However, certain plants like leafy greens appreciate the cooling action of irrigation at mid-day, the gardener will have to weigh whether or not it’s worth sacrificing water to evaporation to please these crops.
In terms of methods, sprinklers are probably the most wasteful way to water any space. They often spray sidewalks and driveways and have their course altered by the wind. However, they can be convenient for covering large areas and work well enough for lawns that don’t need to be watered deeply, although again, morning is probably the best time to do this. Bear in mind though that lawns allowed to brown-out in midsummer usually bounce back just fine when the weather cools down and rains return.
For most plants in the garden, watering cans or sprayers with a number of fine holes in the shower-head provide the gentlest flow for absorption into the soil. Too much pressure from a bad sprayer means that water is bouncing off the ground without penetrating the root zone.
How often you water can also be critical to plant health. Although many plants with shallow roots like annual flowers, lettuces and cabbages may need to be watered every few days, there are other plants for whom this can do more harm than good. Plants like tomatoes, squash and hardy perennials–especially native plants–either don’t require much water or they root so deeply that infrequent irrigation encourages them to send roots farther down into the soil where they are better able to forage for moisture on their own. Soaker hoses can be a good strategy for many of these plants, getting water to where it’s needed most.
Finally, when it comes to trees, make sure to keep them well watered for the first few years after planting with deep and infrequent irrigation that encourages them to root out. Some gardeners accomplish this by periodically putting a hose next to the base of the tree and letting it drip for several hours. But there are also a number of products including “Treegator” watering bags that accomplish the same thing over nine hours or so by dripping a steady supply of moisture into the tree’s root zone. Although these bags are somewhat expensive, it’s easy enough to buy a few and move them around the garden to whichever tree or bush happens to need watering.
Brian Allnutt is a freelance writer and organic gardener in Metro Detroit. You can reach him at firstname.lastname@example.org.