Watering Myths

By Paul James

After a week in the mountains around Santa Fe, with lows in the 50s and highs in the 70s, I was less than excited to return home to sweltering heat and humidity. But then it is the middle of July, after all, so I had no reason to be surprised. After unpacking, I headed out to the garden to water, and that got me to thinking about a number of myths I frequently hear about watering. Seven myths to be exact.

MYTH #1: PLANTS REQUIRE ONE INCH OF WATER A WEEK

I’ve never been a fan of this popular recommendation for two reasons. First, how in the world do you know when you’ve delivered an inch of water to plants? And second, it’s just plain bad advice.

Fact is, the moisture needs of plants vary enormously. For example, newly seeded beds, young seedlings, and new transplants need water every day, maybe even twice a day in summer. The same is true of patio pots and hanging baskets (and in my case at least, bonsai).

Newly planted trees and shrubs are sure to die if they receive only an inch of water a week. It’s best to water them with a slow trickle from the hose, moving the hose around the perimeter of the root ball now and then, ideally for about as long as it takes you to casually consume one beer. Or even two. Depending on your soil type, you may need to repeat the process every three or four days.

Mature trees and shrubs, on the other hand, may not need much (if any) supplemental watering even during the summer months. I occasionally water my tree-filled lawn, but in 40 years I’ve never actually watered a mature tree.

And Bermuda grass can get by with as little as an inch of water every four to six weeks. Fescue, however, should be watered every week.

Now in defense of the myth, I suppose that if everything in your landscape is fully established, meaning every plant has been in the ground for at least three years, odds are most everything growing will survive with only an inch of water a week. But I can assure you few things will actually thrive.

MYTH #2: WHEN PLANTS WILT THEY NEED WATER

That certainly can be the case, but wilting may be due to something other than a lack of water. Wilting can also be a sign of overwatering, because water-logged soils can suffocate plants. And even plants that have plenty of moisture available to them can wilt on really hot days, because they tend to lose moisture through their leaves faster than their roots can take it up.

MYTH #3: WATERING ON A SUNNY DAY CAN SCORCH LEAVES

This commonly held notion is ridiculous. Water droplets don’t act as a magnifying glass on plant leaves.

MYTH #4: AUTOMATIC SPRINKLER SYSTEMS ARE THE BEST WAY TO WATER

I would argue the opposite, actually. Not because there are inherent flaws in sprinkler systems, but because at least 75% of the time the systems are set improperly.

The vast majority of sprinkler timers are set by the installer, whose expertise is in irrigation systems, not plants. So the installer sets the timers to run for 10 or 15 minutes in the morning and very often another 10 or 15 minutes in the evening as well. In most cases, and especially if your gardens are well mulched, that’s nowhere near enough time to deliver a sufficient amount of water to the root zones of plants. Instead, it results in water barely percolating into the soil, which means roots hover in that moist, shallow zone rather than reaching farther down into the soil.

I had an irrigation system for 15 years at a previous home, and I never set it to run automatically unless I was on vacation. Instead, I would turn it on manually to water select zones at different times during the week, and I would adjust the run time of each zone depending on what was growing. I suggest you do likewise.

Now I water by hand, which is in my opinion the only way to know with certainty just how much water every plant gets. And as a bonus, it puts me more in touch – and in tune – with my garden.

MYTH #5: OVERHEAD SPRINKLERS ARE BAD

While it’s true that it’s best to water the base of plants rather than the foliage to minimize fungal diseases, there are times when it’s perfectly okay to water plants overhead. As a matter of fact, after prolonged periods of dry, windy days, I prefer to water overhead to knock off all the accumulated dust on leaf surfaces. What’s more, overhead watering helps cool down heat-stressed plants.

MYTH #6: WATER ONLY IN THE MORNING

Sure, it’s best to water in the morning, but not everyone’s schedule allows for what’s best. Basically, you should water whenever you can. And deep soak each time you water.

MYTH #7: DROUGHT-TOLERANT PLANTS DON’T NEED TO BE WATERED

Even cacti and succulents, which are among the most drought-tolerant plants, need water, especially during their first season. Beyond that, they’ll need water less frequently, but they’ll still need to be watered now and then. In my experience, even drought-tolerant plants grow better with a regular supply of moisture.

THE BOTTOM LINE

Ultimately, the only way to know if your plants are getting enough water is to stab a shovel or trowel into the soil, pull it back to reveal the soil profile, and see for yourself just how deep the water is percolating into the soil. It’s not exactly a high tech method, but it is the best method.