With our hot, dry, Rogue Valley summers, it is so easy to assume that we need to put lots of water on our gardens.
But Marsha Waite, coordinator of the Oregon State University Extension Master Gardener Plant Clinic, tells me they see more plants that are overwatered than under-watered. This is true of houseplants, too. More are killed by overwatering than just about any other cause.
Let's see if we can get to the root cause (pardon the pun!) of some of the misunderstandings about water and plants.
Plants need water in order to keep their tissues healthy, of course. Plant nutrients are carried in their sap, or internal moisture, and plants need to be hydrated, just like people. But plants also need air in the soil in order to thrive, because that is where the helpful aerobic bacteria are found.
Roots do most of the water uptake for the plant, but if all of the available space in the soil is occupied by water, there is no room for air, and the plant will not thrive, even if it's not standing in a puddle of water.
Ideally, the soil will hold some water, while still leaving some room for air. And here is the tricky part — how much water-holding capacity does your soil have? In the Rogue Valley, we have a wide range of soils, from sticky clay and decomposed granite to old, sandy riverbottoms and "manufactured" soil in many of our raised beds. And these all have different abilities to hold water.
Clay, although cursed by many, holds a great deal of water, and for a long time. But that presents the problem of lack of aeration, because the soil particles are small, flat and tend to stick together. It drains and dries slowly, but can quickly turn to "concrete" when it does finally dry out.
The first step in learning how to water is to determine the kind of soil you have. If you have heavy clay or decomposed granite, it can be amended and made less difficult to some degree, but the process may take years of adding compost to your native soil. This is one benefit of growing your veggies in raised beds, where you have more control over the makeup of the soil.
How do you know if you're overwatering? Yellowed leaves, especially on the bottom part of your tomato plants, is a clue. Swampy, squishy parts of your lawn is another. And it may surprise you to learn that plant wilting is often another sign. Yes, wilting may indicate overwatering, resulting from root rot.
What to do? Do not just automatically water because that's how your system has been programmed. Purchase and use a moisture meter, or at the very least, check your soil with your fingers an inch or two below the surface before adding water. Pay attention to how your soil drains. You'll also need to keep an eye on the weather, including wind, in your yard.
Regarding your lawn, set the mower higher in the summer to help keep roots cool. If you have clay under your grass, water it for shorter periods of time instead of all at once. This gives the water a chance to penetrate the soil instead of running off and creating mini swamps.
Probably the least effective way to water is to stand with the hose in your hand and spray water over the plants. It almost always results in underwatering, as you will discover by checking your soil a couple of inches down when you're through. This method simply doesn't allow the water to go deep enough to reach the roots, where it's needed.
There is no watering formula that works for everyone. It requires common sense, taking into consideration your soil, the weather, the garden's location and the plants' needs. Sorry.
Carol Oneal is a past president of the OSU Jackson County Master Gardeners Association. Email her at firstname.lastname@example.org.