Across the US and Canada, many of us are dealing with record-setting high temperatures and garden-withering heat. From those of us at Gardzen: hang in there! This too shall pass and rough seasons are just part of the gardening experience. The hot weather has raised some interesting gardening questions, however, many of which are about water and watering. We got one such question from a reader: what’s the best water temperature for plants? To put it another way, do plants benefit from water that’s hot, or cold, or air temperature/room temperature? As it turns out this is one of those simple questions with a complex series of answers and more than a few gardening myths attached. So let’s dig in and learn more about water temperature and watering our plants!
Gardzen Executive Summary:
· Watering plants properly is vital to their health and well-being.
· Water that’s too hot or too cold can damage or kill plants! Never water with near-freezing water or water that’s near-boiling.
· Each plant has an optimal temperature range for water.
· When in doubt, room temperature (60-80F/15-25C) is probably best.
· Give your plants all the water they need, but try to avoid over-watering.
Optimal Water Temperature for Watering Plants
All plants need water to live, but how much and how often they need water varies widely from plant to plant. Likewise, optimal water temperature for watering plants varies from species to species and even sometimes from gardening space to gardening space. Most of us are familiar with the basics: most plants need more water in hot, dry, or windy weather. Tropical and subtropical plants tend to require more water than cacti, succulents, and other desert-dwellers. Outdoor plants in containers may need more water or more frequent watering than in-ground plants. It’s generally best to water first thing in the morning or just before sunset so that plants don’t lose vital water to the heat of the day. However, water temperature matters too, and it’s both more complex and more simple than we might think.
Most plants prefer water that’s around 68F/20C in temperature. This is the temperature level that allows for maximally efficient water and nutrition uptake and the easiest, healthiest experience for the plant. Now we’re not suggesting that everyone start measuring the water temperature and make sure that our watering cans are at exactly 68 degrees; most plants are perfectly happy with water that’s anywhere between 60-80F/15-25C in temperature. There are of course exceptions. Tropical plants may prefer water that’s between 75-90F/24-32C and succulents/cacti may have wider or more narrow ranges depending on the environment in which they evolved. As always, we need to get to know our plants, do good research, and learn what they need so that we can keep them healthy and happy.
Avoid Extremes When Watering Plants
We’ve written before about the perils of over-watering or under-watering plants; both can lead to weakened plants, illness or infection, or plant death. While losing the occasional plant is just part of having a garden space, it’s import to (again) know our plants and avoid over-watering or under-watering. It’s also important to avoid extremes of temperature in the water we give our plants. Let’s talk a bit more about that.
In a previous blog we dispelled the myth of watering plants with ice cubes. To recap, while this make look like a handy way to give our plants a steady stream of cool water, the reality is that near-freezing water and exposure to ice can easily damage plant roots and injure, weaken, or kill our plants. It’s important to remember that the same is true on the other extreme of temperature: water that’s too hot can harm plants as well. For most plants, temperatures above 90F/32C are risky. Water this warm can cause stress, withering, and root or foliage damage. Depending on the plant, water above 100-120F/37-48C is sure to cause some damage and may kill the plant. Water that’s close to boiling (212F/100C) will kill plants, period.
Does this mean we need to be paranoid and obsessively check the water temperature before we water our plants? Not at all! It does mean being aware of where your water is coming from and how hot or cold it’s likely to be. Here at the Gardzen Test Gardens, we love our rain barrels and rainwater collection system. However the water in those barrels can get HOT after a day in the sun, so we’re careful to use water from barrels that live in the shade, or to use rain barrel water first thing in the morning when it’s cooler. On super hot days, we’ll use water from the hose that’s a least a bit cooler after traveling through underground pipes. Likewise in winter we’ll water when the rain barrels have had a bit of time to warm up, or we’ll use hose water that comes at a more moderate temperature.
Awareness and Gardening Success
It all comes down to awareness. When we know better we can do better and now that we know a bit more about water temperature we can approach watering our plants with some awareness of what temperature water plants need and how to avoid extreme temperatures when watering plants. It’s going to be a hot summer for many of us, so paying attention to water temperature when watering plants can help us keep our gardens as healthy as possible when the weather is scorching.
For everyone dealing with the heat wave, please hang in there. Keep yourselves, your pets, and your plants as safe and healthy as you can and remember that this too shall pass.
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