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Grow Up Here: Believe it or not, watering your plants too much can do damage

Uh, uh, don’t touch that tap until you read this article!

I’m somewhat embarrassed to be writing this essay. After all, we’ve had plenty of rain for our gardens so far in the 2021 growing season. But that hasn’t stopped you from watering anyway, right. Why? Because, as everybody knows, watering your garden, faithfully, thoroughly, even generously, is the most important task a modern plot-tender can render. 

And, there may be only one person in horticulture who disagrees with that, and, unfortunately it is the present author. So, here’s the thing…or at least his thing.

One summer, several decades ago, there were days so hot that people in New York City were filmed frying eggs on a sidewalk (without a barbecue). 

This author, walking home from work, would pass a neighbour who punctually watered a beautiful backyard garden each day. And it obviously paid big dividends: that neighbour’s corn was eight feet tall (i.e., 2.4384… m). 

The author’s corn was only three feet tall (0.91 m), for his well had gone dry. Then, the temperature soared to 40ºC. By the end of each day, the author’s corn had wilted so badly that it was sprawled out on the ground. 

One would think that the neighbour’s corn would have done much better, even thriving under these conditions (as corn likes heat), but alas that was not to be, for the neighbour had gone on vacation that week. 

There was no need for the neighbour to cut the vacation short to water the plants, because by about the second day of the heat wave, those beautiful corn specimens were crisp and dead. The author’s corn survived, in a manner of speaking, and eventually produced a wonderful crop, something dead corn cannot do.

If this sounds like a fairy tale, let me correct that impression. It is not a lie, not even an exaggeration, nor is it a fable, although it has a moral. The parameters, while extreme, are accurately portrayed; they just don’t happen so dramatically very often. And the lesson they suggest holds true, every growing season, and becomes more important every year as we march inevitably towards the day when we cannot afford to water our gardens.

The lesson is this: If you water your garden frequently, say, daily, the plants that you water will develop roots near the soil surface, expecting their daily drink. Come drought, and northern Ontario usually has one every summer, those plants need that attention even more so, just to sustain them. But that is not what the modern gardening term, sustainability, means: dependence. Those gardeners, whom I will refer to in fun as “aquifers” (literal translation, “water-bearers”), are now tied to their gardens in an unhealthy relationship.

Lest you think that the only alternative to the thoroughly-watered plant is an unhealthy plant, think again. Plants, like pets, must be trained, and the time scale for the plant training is not of evolutionary order but coincides with any one growing season. We could use corn as an example, but let’s use tomatoes, since almost every gardener grows them. 

When you plant a tomato seed, indoors or outdoors, water it thoroughly the first day, and keep the ground from drying out, until the seed sprouts. Now, already, there is an attitude adjustment to make: the sprout poking through the soil is a sign that the watering must become much deeper. 

For if there is a 2 cm sprout that you can see, there may be a 4 cm root that you don’t see. If you don’t water at all, that root will continue down and down until it strikes a vein of water; or does not. In a pot or a planting tray that root may not find water farther down; hence the need for frequently watering potted plants. 

But in a garden soil, usually the deeper you dig, the cooler and more moist the soil is. So you “train” your plants early on to go down and down for that moisture. Where I live, in Naughton, you might not find plentiful water until more than three metres down, but massive though a garden tomato’s root system is, it will not usually get more than 1 metre down. 

So, the method is ultimately doomed to failure? No, otherwise, why would I write an article about it? The method of withholding water is destined for success, because, water percolates “upward” in a garden soil, from the water table, or at least from more moist lower depths, up to the root zones of the garden plants. 

So, if you see a layer of dust, several centimetres deep surrounding your plants, you still should not water? The answer comes in two parts: First, consider the dust around the garden plants to be a mulch (yes, a “dust-mulch”), protecting the roots from heat and sun. Second, the plant, not the dust mulch will tell you when the plant needs water. If it does, then water thoroughly, and generously. If not, wait. 

In dry-land gardening, the unwatered plant grows more slowly, on top, but underground is putting its energy into its root system. When the mid-August rains come, that deep and massive root system will drink up every drop of rain in late summer, and the plant will make up any deficit that seemed to be a consequence of this method of “tough love.” Oh, and weeds tend not to germinate in a dust mulch, while if you water frequently, you are sprouting countless weed seeds!

Not convinced? I would not have learned this either, had it not been for a dry well and a severe drought.

Ron Lewis is known to many in the north as 'the tree guy' due to his experience with growing fruit in cold climates. He is a home-based food producer and a student and practitioner of organic gardening methods, using natural materials and traditional cultural methods in place of chemical fertilizers, herbicides and pesticides.