The Literary Gardener – September 2016

“Water is the vehicle of Nature.” ~Leonardo da Vinci, “Codex Atlanticus” c.a. 1600

The great “Renaissance Man,” Leonardo da Vinci, was obsessed with water. Over and over again he drew water—flowing, falling, whirling, raging, destroying. Da Vinci’s series of black and white sketches, called “The Deluge,” depicts a torrential apocalypse, perhaps drawn from his boyhood memories of the Arno River flooding over its banks and devastating the city of Florence in 1466. Eerily, the same disaster occurred in the city exactly 500 years later in 1966.

Da Vinci was determined that humans have the ability to harness the power of water, and he illustrated numerous devices that would move water, stop water, raise water and drain water. The irrigation systems that farmers and gardeners use today depend on the science of how water flows, which Da Vinci worked out in his drawings, centuries before the field of fluid dynamics was established.

Indeed, the ease with which 21st century gardeners are able to utilize water may be harming our plants. I checked in with Peggy Bruce and Dolly Travers, specialists at the OSU Extension Service Plant Clinic, and they said the clinic sees far more plant problems related to overwatering than not watering enough, even during the hottest part of summer. Peggy noted, “A great many gardeners seem to think that by turning the water on and off they have fulfilled their responsibilities.” It’s all too easy to develop this attitude when our automatic irrigation systems do most of the watering work for us.

Instead, we need to follow da Vinci’s lead and endeavor to harness the power of water. Toward that aim, Peggy and Dolly offered these reminders for effective garden watering:

First, know each plant in your garden, particularly its requirements for water. Learn which plants need lots of water and which ones are drought-tolerant (Shooting Star Nursery in Central Point has a terrific online list). Some plants such as Pelargonium, Echeveria and Daphne, are especially sensitive to overwatering. Peggy said, “I almost killed a pricey Acanthus spinosus recently, in part because my above-ground sprinkler system blasted it. Now, I put a bucket over the plant when I water, for protection.”

Second, invest in a good moisture meter and use it frequently. Probing several sides of a plant a few inches beneath the soil’s surface will provide a more accurate picture of the plant’s moisture needs. Remember that temperature, humidity and wind-velocity all influence a plant’s water requirements. In addition, clay soils hold water longer than sandy soils, and exposure to full sun all day will dry out plants and soil more rapidly than if plants are in partial to full shade.

As the sun continues to lower in the sky this month, keep in mind that the watering schedule that worked in your garden several weeks ago will probably not be appropriate now; make adjustments to the time and amount of watering accordingly. Also, a watering schedule that works for one part of your garden may not be optimal for other areas. Fine-tune your irrigation by using a moisture meter to identify garden areas that hold water longer or dry out faster.

Third, water plants deeply but not more frequently than necessary to maintain the soil moisture level recommended for each plant. Plants should dry out a little in between watering, but don’t wait until the leaves wilt to water. Drought-stressed plants are more vulnerable to insect infestations and diseases that can overwinter in the soil and become problems again next year.

Fourth, when setting out new plants, keep in mind that even drought-tolerant plants need adequate water for the first year or two. Once established, they’ll require minimal water to thrive and may fare poorly if overwatered.

Through his drawings, Leonardo da Vinci expressed fear that too much water would overtake humankind. Today, when drought is uppermost on gardeners’ minds, it’s ironic that it is far more likely that too much water will overtake our plants by our own doing. Like da Vinci, gardeners must make plans to prevent such a calamity, while also recognizing that, as the “vehicle of nature,” water will hold onto some of its mysteries. After all, as anthropologist and author Loren Eiseley wrote four centuries after da Vinci, “If there is magic on this planet, it is surely contained in water.”