Author: Rebecca Last, Gardening at LastMaster Gardeners of Ottawa-Carleton;

Why bother to save water?

In my house, water bills are a big motivator. Like many municipalities, Ottawa has graduated water bills. Like graduated income tax, the marginal cost of water increases with usage. A cubic metre (m3 ) is 1,000 litres of water, roughly equivalent to 28 showers or 13 baths. If you use less than 6 m3 per month, you only pay $0.83 per m3 for water, plus another $0.75 per m3 for storm water infrastructure, for a total of $1.58 per m3. However, the next 18 m3 will cost you nearly double this amount. After that, prices continue to mount.

Add environmental challenges like the extreme weather events brought on by climate change and the overall depletion of ground water, and there are plenty of reasons to save water. For this avid gardener, water-wise gardening means:

  • Preventing run-off rainwater,
  • Harvesting rainwater,
  • Using best watering practices,
  • Conserving soil moisture, and
  • Designing according to hydrozones.

Prevent Run-off Rainwater

Our first step in being water-wise is to make the most of the rain we get. This means analyzing where rainwater runs off our property and then redirecting it to keep it in our gardens. Two principal techniques to prevent rainwater runoff are:

  • Redirecting downspouts away from hard surfaces and onto permeable surfaces, like lawns and garden beds; and
  • Building a rain garden to capture and store rainwater run-off.

Many municipalities, including Ottawa, offer water-saving advice to homeowners. There are also lots of DIY sites where you can learn how to design your own rain garden.

Harvest Rainwater

When it comes to harvesting rainwater, many homeowners already use water barrels but have you considered also collecting household grey water? Grey water is surplus household water, including wash water. It is distinct from black water, another term for sewage. During the winter, I keep a watering can in the basement utility sink. A small hose feeds the condensate from our gas furnace into this watering can, collecting 2-3 liters every day. My indoor grow-op is right next to the room where the sink is located. As the furnace condensate is essentially distilled water, it is ideal for my delicate seedlings. (Note, our furnace is natural gas.). (If you have propane furnace, check the acidity of this condensate before using it on plants.)

During the summer, we run a dehumidifier in the basement. One of the mysteries of Ottawa weather is that months when it is most humid inside are also times when we often experience droughts outside. The 6–8 liters of water from my dehumidifier are a welcome addition to an outside raised bed.

Folks who live on well water can be creative with their grey water-saving techniques but there are risks. Robert Pavlis’ Garden Myths website (https:// identifies three main issues: gray water chemistry, bacterial content and pH. Common ingredients of soap include sodium, boron and bleach, all of which can damage plants, especially plant leaves. Grey water used for washing may also contain bacteria, including fecal matter, so it’s best not to use this water on food plants. Those chemicals in soap tend to make the water more alkaline, sometimes to the point of harming or killing plants. It’s definitely not a good idea to use grey water on acid-loving plants.

Best Practices

What do we mean by “best practices” for watering? We mean watering at the right time of day, preferably early in the morning, and not at midday when more water evaporates. Also, many plants go dormant during the heat of the day, so can’t use water then. Watering deeply but less frequently encourages plants to send their roots deep into the soil, which generally makes these plants more able to withstand drought.

It’s also worthwhile investing in precision watering technology. The cheapest of these techniques is to buy watering spikes and attach them to old pop bottles with the bottoms cut off. I’ve tried them but they didn’t work well in my sandy soil. Either the little holes in the watering spikes clogged and didn’t drain properly, or they drained so well the pop bottles emptied right away. Drip irrigation hoses and “snip and clip” precision irrigation systems are more expensive but more effective options.

Conserve Moisture

The first step in preserving soil moisture is to amend your soil. I garden on what is essentially beautiful white sand—the beach-goer’s dream but a nightmare for gardeners. Even with all the organic matter that I’ve added over the years, my garden still has “excellent drainage” but almost no water retention. I plant densely, so groundcovers form a ‘living mulch’. I use organic mulches in areas where the plants need more spacing and, on hot days, I sometimes put up a sun umbrella to provide shade to crops like lettuce that don’t like the heat.

At this point, you may be thinking that being water wise means planting only sedums, cacti, and yuccas. Nothing could be further from the truth. In fact, Linda Chalker Scott, an adjunct professor of horticulture at Washington State University, points out that xeric plants have evolved, like camels, to use whatever water is available. As a result, studies have shown that many well-meaning gardeners who implemented xeric plantings used more water.


The key is to plant the right plant in the right place, making sure each new addition gets the care it needs to become well established. Dividing your garden into “hydrozones” will help you pick the right spot for each plant. The idea is to map out your garden according to areas that are naturally dryer or wetter, or have easier access to water, and plant accordingly. This approach will save you time and money, and help you conserve water.

You can still have a lush-looking garden while saving money and feeling virtuous about your minimal water consumption!

Tip for Plants Bought at a Garden Center

Plants purchased in garden centres are often very dry. Once home, plunge the pot in a bucket of water up to the rim. More often than not, the pot will float, indicating that it is dry. Leave the pot in the water until sinks, this could take a couple of hours, lift out and allow to drain. Leave the plant overnight and it should be nice and turgid for planting the following day.

Tip For Planting in a Dry Garden

When planting into a dry garden, after digging the hole, fill with water one or more times and allow the water to soak into the soil. Plant the plant and water until the water puddles on the soil surface. Mulch.

Visit a Botanical Garden For Unique Experiences.

More on Gardening Calendar