Seattle Press on Line - August in the Garden

August in the Garden

By Kimberly Christensen

Aug 01, 2002 -- Sometimes on a sunny, long summer evening, when I should be lying in my hammock and catching up on my stack of novels, I find myself wishing for rain. With horror, I quickly stop the thought. How can I wish for rain on such a beautiful day? The answer comes to me slowly. It's been nice outside for 4 days now, and the forecast calls for more of the same. If this keeps up, I'm going to have to water.

One benefit of living in Seattle is that we can be lazy waterers. If we just hold out a few more days it will rain, and then we will be spared this task. Also because of our wet weather, many of us opt not to install irrigation systems. This combination of not needing to water frequently and not having an irrigation system means that many of us are uncertain as to how much we need to water, and when.

Water requirements depend on the type of plant, the type of soil and the weather. Annual plants, new plants and plants with shallow root systems (most veggies and bedding plants) need to be watered more frequently than established plants and plants that form deep taproots, which can absorb moisture from deeper soil. Sandy soil necessitates more frequent watering because it does not retain moisture well. Clay soil accepts water more readily but can't be watered too frequently. Compacted soil, which does not absorb moisture well, will often erode rather than retain water. Hot weather causes water in the soil to evaporate. It also causes plants to transpire more rapidly, which means that they lose considerable amounts of water through their leaves.

Plants that wilt send a clear message that they are thirsty. However, wilting stresses the plant and can cause growth to be stunted. Rather than rely on foliage for clues, go straight to the soil. For a quick assessment, poke your finger a couple of inches into the soil to see if it is damp. If it's not, it's time to water. Digging down 5-7 inches allows you to more thoroughly assess the watering situation. Scoop up a small ball of soil and compress it. If you see drops of water, you don't need add more. If not, gently toss the ball a few inches into the air and let it fall back into your palm. If it crumbles, it's time to water.

Many gardeners believe that plants shouldn't be watered mid-day because the water will cause the leaves to be sunburned. While the combination of water and sun may cause spots to form on leaves, this isn't often a serious problem. The problem with watering in the daytime is that much of the water will evaporate before the plants make use of it. In summertime, watering in the morning or evening makes your water go farther (and lowers your water bill). If slugs or snails plague your garden, consider watering in the morning, as evening waterings are more likely to attract these little pests.

Applying a layer of mulch to your garden can prevent evaporation. Mulch helps trap water in the soil and allows the roots more even access to moisture. It also reduces runoff and erosion. As mulch decomposes, it also replaces nutrients that are used by the plants are lost in runoff.

Plants should be watered where their roots are. Watering vast expanses of soil can cause erosion, leach nutrients, waste water, and get expensive. A drip irrigation system, which can be set up before or after plant your garden, delivers water right to your plants and can be an efficient use of your time and water. However, if you don't want to install one, water your plants by hand with a watering can or a hose attachment ("fan" or "rose").

If you water by hand, aim for the soil so that water doesn't splash up onto the plant and transfer disease-causing soil microbes onto the foliage. Tilt the spout upwards to allow the water to sprinkle rather than pour. Remember that you're trying to imitate a gentle rain, not a flood. Allow time for the water to soak in. If you notice runoff, move to another location while the water soaks in. Check the soil in a few minutes to see how much water has soaked in. Continue watering if the layer under the topsoil is not yet wet.

A few hours after you've watered, check the soil again to see how deeply the soil is moist. This will help you learn how effective your watering is and whether you should increase or decrease the amount you're watering. If you are using a drip system, you can use a similar test. Let the drip system run for 15 minutes. Wait a few hours and then test your soil. Adjust the watering time as necessary.

Keep in mind that over-watering can be as detrimental to the health of your plants as under-watering. Over-watering can cause roots to rot and can promote the growth of harmful soil microbes. It also causes erosion and nutrient loss. Certain plants, like tomatoes and melons, actually like to be under-watered when their fruits are ripening. However, other plants, like leafy greens, need plenty of water as they mature. Learn more about your plants watering needs so that you can adjust your technique as necessary.

To learn more about drip systems, visit www.ci.seattle.wa.us/util/lawncare/smartwater/default.htm, a Seattle Public Utility website, where you can download a Smart Watering brochure. For those without internet access, you can call the Natural Home and Garden hotline at (206) 633-0224.

Kimberly Christensen lives and gardens in Wallingford.

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