Why I Only Water My Garden Once a Week

During the driest part of summer, it can feel instinctive to head outside every evening and give the garden a little water. The soil surface looks dry, plants might droop slightly in the afternoon heat, and it's easy to think that surely more frequent watering must be better.

But in my garden, I generally do the opposite.

I water deeply, usually only once a week. This is not because my garden needs less water than everyone else's. It is because I want the water I apply to actually penetrate deep into the soil to reach the root zone, and encourage plant roots to grow deeper and become more resilient between waterings. This is called deep watering.

There are exceptions, of course, such as newly planted plants, seedlings, containers, hanging baskets, and shallow-rooted vegetables, which may need water more frequently. Extreme heat, sandy soils, and unusually windy weather can also change the watering schedule. But for most established perennial beds, shrubs, trees, and many vegetables, I would much rather give the soil a thorough soaking once a week than sprinkle a little water over it every day.

The Problem With Watering Every Day

When we water for only a few minutes, we often wet just the upper layer of soil. That soil may look beautifully dark and moist when we finish, but dig down several inches and you'll likely find that it is still completely dry near the roots.

Most plant roots grow where conditions allow them to access water, nutrients, and oxygen. When water is repeatedly concentrated close to the soil surface, plants develop a greater proportion of their active roots near the upper soil layer. Those roots are then living in the part of the soil that dries out fastest during hot weather, making your plants more drought-prone. Thats why I recommend deep, less frequent watering to encourage deeper, healthier roots and greater drought tolerance.

What Infrequent, Deep Watering Actually Does

Deep watering means applying water slowly enough and for long enough that it penetrates well into the plant's active root zone.

A light sprinkle might wet the first couple of centimetres of soil but sun, heat, and wind can quickly remove some of that moisture through evaporation. A long, slow watering allows moisture to movedeeper into the soil profile. Once water is deeper underground, it is better protected from evaporation and remains accessible to roots for longer.

Someone watering for five minutes every day may actually be supplying less useful water to their plants than someone watering slowly once a week. Colorado State University Extension gives a great example of this problem; a supposedly efficient irrigation system running for 15 minutes every three days was applying only about one eighth of an inch of water each time and much of that water was essentially being wasted because it was not penetrating deeply into the soil.

Deeper Roots Make More Resilient Gardens

One of my goals as a sustainable gardener is to grow plants that are climate-resilient and can handle some fluctuation in their environment. I don't want my established plants completely dependent on me to water them after a hot day, I want them to have deep, healthy root systems that can access in ground water.

Deep watering helps create the conditions for roots to explore a larger volume of soil that gives it access to a much larger reservoir of moisture and nutrients. That becomes particularly important during drought.

Root depth is't just determined by the amount of water its given but also by species, soil texture, compaction, drainage, oxygen availability, and other enviromental conditions. And some plants are just naturally shallow or deep rooted.

How Much Water Does a Garden Actually Need?

A commonly used metric for many garden plants is around one inch of water per week, including rainfall, although individual plant needs vary considerably. Generally, many plants can do well with roughly this amount delivered less frequently rather than being given small amounts every day.

I prefer thinking in terms of soil moisture rather than a rigid watering schedule since time of year, weather, humidity, wind and other climate factors can affect your plants' water needs. Your soil will tell you much more than your calendar does so stick your finger into the soil! Or, better yet, use a hori hori and actually look several inches down.

If the surface is dusty but the root zone is still cool and moist, there may be absolutely no reason to water.

If the soil is dry several inches down, it is probably time.

Adjust Your Watering to Match Your Soil Type

Generic advice like "water once a week" can be a little misleading since each garden is unique. Some general rules of thumb for watering specific soil types are as follows;

Sandy soils have large pore spaces and allow water to infiltrate quickly but also drain quickly and have lower nutrient-holding capacity, so they generally need more frequent irrigation.

Clay soils hold considerably more water, but they absorb it slowly so applying a large volume too quickly can result in puddling and runoff instead of deep infiltration.

While loamy soils tend to fall somewhere in between.

My soil is a sandy loam, which is ideal for once-a-week watering, so when I say I water once a week, the important part is not really the once a week, the important part is that I water deeply and infrequently.

Your garden may need deep watering every five days, every seven days, or even less frequently depending on your soil, plants, weather, shade, and the amount of rain you have received.

Sustainable Watering Tips

Slow Water is Better: One of the easiest ways to water deeply is simply to slow everything down.

I prefer a slow trickling hose, drip irrigation or soaker hoses whenever possible because they deliver water directly to the soil. Slow application gives the soil time to absorb the water.

Mulch Makes Deep Watering More Effective: A layer of organic mulch shades the soil surface, reduces evaporation, moderates soil temperature, suppresses weeds, and helps preserve soil moisture.

Approximately two to three inches of organic mulch around garden plants helps conserve soil moisture.

Water deeply. Cover the soil. Let the soil hold onto that water.

Let the Soil Dry Slightly Between Waterings: Plant roots also need oxygen, so healthy soil contains pore spaces that alternately hold water and air. When soil is continuously saturated, those spaces stay filled with water and oxygen availability can decrease. Allowing an appropriately drained soil to lose some moisture between irrigation cycles helps maintain that balance.

Established Plants and New Plants Are Different: This is the biggest caveat to my once a week approach. I do not treat newly planted plants the same way as established plants.

A newly planted perennial, shrub, or tree has a relatively small root system. It cannot access moisture throughout the surrounding soil yet so new transplants need closer attention while their roots establish.

Seeds and tiny seedlings are another exception because their roots occupy only the uppermost portion of the soil.

Containers are completely different again since a pot contains a finite amount of soil and can dry remarkably quickly during summer. Some of my containers may need water every couple of days even while the garden beside them goes an entire week without irrigation.

I Want to Grow a More Self-Sufficient Garden: I want to work with the ecological processes already happening in my garden rather than constantly compensating for the way I have designed it. That means building soil with organic matter, keeping soil covered, choosing plants suited to the site's existing conditions, allowing plants to develop healthy root systems and watering in a way that encourages resilience rather than dependence.