In Gardening, You Can’t Always Count on Rainfall

Eventually, every gardener does have to do a bit of watering. So, let’s look at some effective ways of doing it.

Larry Hodgson has been writing a weekly horticulture column for the French-language newspaper Le Soleil de Québec for 37 years. I thought you might like to check out some of these articles from way back in time.

When I found this one on irrigation, I was surprised to find how current it was! Many municipalities in North America have been enacting new by-laws on the watering of plants in the past years to drastically reduce the amount of drinking water being used for gardening use, especially irrigating lawns. I find this article explains how, why and when to water your garden and make a smarter use of this essential ressource.

Mathieu Hodgson

July and August are the driest months in most Northern Hemisphere temperate climates. And even when rain does fall, intense summer heat can cause serious evaporation and the result is drier soil. Does that mean you should immediately get out the old garden hose and soak your plants?

Not necessarily. For those not living in a truly arid climate, you’ll find most locally adapted plants will cope very well on what Mother Nature has to offer. Well, most of the time, at least. A little bit of drought stress is actually good for many plants. It pushes them to develop deeper roots through which they can harvest moisture from deeper within the earth. In years of nearly constant drizzle, their roots remain superficial and susceptible to damage. When it becomes dry from time to time, they’re much more robust and resistant. Of course, that will vary according to the season: no two summers ever seem quite alike.

Most permanent, well-established plants grown in the ground don’t need to be watered unless there is a real drought (several weeks with much less precipitation than is normal for that region). On the other hand, some categories of plants need more water than others: it’s the latter that may need watering before drought conditions occur. Obviously, you only need to water even these if it doesn’t rain at all or only very little.

Recent Plantings

Even xerophytic plants, that is, ones naturally suited to dry soils, need watering when freshly planted. A thorough weekly watering for three or four weeks is enough for fast-growing plants, such as annuals and perennials. For trees and shrubs, extend the watering period to the entire first summer. Even to two years for the slowest rooters, like rhododendrons, azaleas and magnolias. A recently sown or laid lawn may require watering every two or three days for the first 50 days!

Plants Growing in Rain Shadows

Plants planted under trees, especially conifers, or an awning or roof projection, etc., are in a rain shadow, a spot not much precipitation penetrates. They can therefore run out of water even when the rest of the garden is thoroughly moist. Always remember to give extra water to plants living under such specially stressful conditions.

Bog and Marsh Plants

Gardeners often plant wetland plants, such as astilbes, ligularias, Siberian irises, rodgersias and lobelias, in normally drained soils without realizing they’re not as drought-resistant as their neighbors. And, usually, everything is fine, especially when you mulch them. Except that, in times of drought, these plants, which have no innate resistance to drought, are the first to suffer from a lack of water. If you don’t water them, you may lose them!

Potted Plants

Plants growing in containers are more sensitive to a lack of water than other plants. Their roots are contained within a barrier and can’t reach out to find moisture elsewhere. And the smaller the container, the more this applies. Sometimes you need to water them daily. Even twice a day if there are several plants in a small pot.

Plants Growing in Sand

Sand retains almost no moisture. Plants grown in sandy soil may therefore require watering up to twice a week, even if they are well established.

Vegetables

For a bountiful, delicious harvest, don’t stress your vegetables with either too much or too little water. They’re Goldilocks plants: they like their moisture “just right.” Grow them in well-drained soil to allow excess water to drain away. And water, if necessary, so that the soil always remains at least a bit moist. To maintain a more constant level of humidity, a good mulch is very important.

Plants That Can Get By Without Watering

If you choose the right plants for your garden, you can almost forget about watering, because several species tolerate without flinching the worst droughts.

Lawns

Most turf grasses have the ability to go “summer dormant.” They dry up and turn yellow, to the point of looking dead, but then quickly green up again with the return of the rains. It’s therefore rarely necessary to water an established lawn.

Trees and Shrubs

They may require some watering in the first year, while their root system develops, but subsequently, thanks to its extensive length, they can harvest water from deep in the ground. Of course, there are exceptions, but most hang on quite a while under drought conditions. Don’t stress them needlessly, but . . . put them at the bottom of your watering list. And in climates where droughts tend to be short, they almost never require extra watering.

Xerophytes

Succulents, such as sedums, houseleeks and yuccas, as well as plants naturally growing in sand dunes and in arid regions (arbutus, buffaloberries, mugworts, etc.), are very resistant to the worst droughts. In fact, they’re often more successful if you don’t water them. In general, plants with silvery, leathery, or fleshy foliage are drought resistant.

How to Water

Ideally, you’d always water without moistening the foliage. Sprinklers waste a lot of water by shooting water into the air and it then mostly evaporates. And, almost as bad, it covers the leaves in moisture, leaving them more prone to diseases. (Diseases are more likely to develop on damp leaves.) 

If you have no choice other than to use a sprinkler to water, at least do it early in the morning if you can. Like, before 6 a.m.! That’s because at that time, it’s usually cooler and there is little water loss due to evaporation. That makes your watering more efficient. Moreover the leaves dry out quickly under the rising sun. 

Avoid watering in the middle of the day. That’s when water loss to evaporation is at its most severe!

Evening watering is not ideal either, as the foliage tends to remain moist right through the night, a serious invitation to disease. Curiously, some municipalities require that you water at nightfall. It almost seems like they absolutely want their citizens’ plants to suffer from leaf diseases!

The Right Tools

Obviously, to water effectively, you need to have the right tools. Here is a short list of the most popular and useful watering tools. It’s up to you to decide which ones you need.

Mulch

A mulch is a layer of organic matter you place on the surface of the soil. By shading the soil and slowing air circulation, mulch almost completely eliminates soil evaporation and keeps the soil moist much longer, even without the help of rainfall or watering. It takes a good, thick layer—at least 2 to 3 inches (5–8 cm)—to be effective. You can use commercially available mulch, such as cedar mulch, cocoa husks and buckwheat hulls, or homemade mulch.

Garden Hose

A basic tool to bring water to the various water diffusion devices. Beware of inexpensive couplings that have little resistance to pressure and last only a season or two. Brass couplings are preferable. Look for five- or six-layer casings that offer a long warranty: they’re more expensive, but make real long-term bargains, as they’ll last for many years.

Soaker Hose

This hose, often made of recycled tires, is pierced with thousands of holes and is not only the most efficient watering system there is, but also the least expensive! You just have to lay it in places in your garden that are always tend to be dry and cover it with soil or mulch to hide it from sight. Then connect it to a hose whenever you need it and turn on the water. Water immediately starts seeping into the soil, without spraying upward or running off, reducing evaporation to almost nothing.

In addition, you can use soaker whenever you want: no one even need know that you’re watering. So if you accidentally water on the wrong day of the week according to local water restriction bylaws, that can remain your little secret. I don’t even feel guilty for encouraging people to bend the law in such a way, because soaker hoses help save water, which, basically, is the purpose of municipal watering bylaws!

Watering Cans

More convenient than you might think, a simple watering can is useful for watering pots and hanging baskets, of course, but also for newly installed plants you add to an already planted garden, therefore among well-established plants that don’t need watering. With a watering can, you can do “spot watering” and water only those plants that need it. And you can do so without damaging any of them. (When you drag a hose behind you to spot water, it always seems to pull out or flatten a few plants in the process.) 

Watering Nozzles

Watering nozzles and wands, which attach to the end of a garden hose, are really only useful for watering containers and for spot watering (i.e., watering two or three newly planted plants in a well-established flower bed). It would take too long a time (two to three hours!) to effectively water a lawn or a large flower bed with such a tool. Even if you water a small vegetable bed, remember: long and deep watering, not fast and shallow. So take it easy!

Sprinklers

Whether oscillating or rotary, sprinklers are great wasters of water and should only be used when no other method of watering is possible. Indeed, by shooting water into the air, the better part evaporates and never reaches the soil, especially if you water in broad daylight. On the other hand, sprinklers are useful in cases where a soaker hose cannot be used, such as on a lawn.

Drip Irrigation Systems

Especially useful for watering pots, baskets and raised garden beds. And every just about everthing in arid climates! A good drip irrigation system can be a real workhorse, removing a lot of boring watering work, especially if your containers normally require one or two waterings a day. A timer is not only useful, but almost mandatory.

Timer

Very useful for any system that is minimally automated (soaker hoses, irrigation systems, etc.), because it turns the water off after a preset period. So, you don’t have to be around to tell it to stop. The simplest ones only turn off the water flow: you have to turn them on manually. The most sophisticated are fully programmable and will turn the water off and on throughout the summer, according to a pre-established schedule. Imagine! You can finally go on a 3-week vacation and the plants will still get the water they need!

In the case of a programmable timer, you’ll need to add a rainfall detector to your system so it skips waterings in weeks when rainfall has been sufficient.

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There you go! As you can see, watering effectively is not complicated. With the right tools and appropriate techniques, you can successfully water your gardens and lawns while respecting the environment.

Article translated from French by Mathieu Hodgson.