Should You Water Plants With Warm Water?


Pink watering can pouring water on plant.

That kettle that’s been sitting on the kitchen table has cooled to warm water. Is it okay to feed it to the plants? For us, drinking warm water brings health benefits, but does it really make a difference for plant life?

You should water your plants with warm or room temperature water, as it mimics rainfall’s natural conditions. If you use water that’s too hot, you may boil your roots and damage the helpful microorganisms in your soil. On the other hand, ice cold water is also not advisable as it may shock the roots.

To answer whether it’s appropriate to water plants with warm water, we need to understand the impact of water that is too hot and too cold, so we can find the right balance.

In this article, I’ll discuss common plant water preferences. I’ll also look into the science of why one temperature might work better than the other. Finally, I’ll talk about what happens when you water your plants with cold water.

Firstly, What Is “Warm” Water?

For this article, let’s start by being clear about what warm means. Warm means room temperature that is no more than 75 degrees Fahrenheit (23.89 degrees Celsius). The right temperature for your plant may depend on the type of plant you’re growing, but you should always assume that it needs warm or room temperature water.

Think about it this way; before plants were brought indoors and grown for fun, they were grown outdoors. Rainwater was all they had to survive on. Rain that falls from the sky is rarely cold and rarely hot. Instead, it’s usually at a warm temperature. This is especially so during tropical rainfall and storms, whereby you might find the rainfall is even warmer.

The Ideal Temperature for Plant Watering

It’s a good rule of thumb to stick between 62 degrees Fahrenheit and 72 degrees Fahrenheit (16.67 to 22.22 degrees Celsius) for your water. Stick to the cooler side if it’s extra hot out there, and on the warmer side if it’s pretty cool. This is what is considered “warm” or “room temperature” for your plants.

Warm, by your definition, may be the kind of water you shower in. However, this is not warm for your plants, rather, it’s hot. The average person showers in temperatures ranging from 90 degrees Fahrenheit to 112 degrees Fahrenheit (32.22 to 44.44 degrees Celsius), which would scold the roots of your plants.

Warm is typically the best water for your plants, but don’t go overboard. It should be warm at the point it gets to your plants. As already noted, hot water can ruin the roots and damage the soil. Also, if the water is a little cooler than “warm,” but it’s hot outside, you don’t need to stress too much about warming up the water.

Ice Cold Water Can Damage Plants

Depending on the temperature outside, cold water can also be detrimental to plants. When it’s cold outside, cold water only gets colder. Your plants are most likely struggling with the cold temperatures anyway, so warm water would be especially ideal in this situation.

Nevertheless, don’t let this be an excuse to use the kind of cold water that might refresh you during a heatwave. On the other hand, don’t go too far on the other side of the spectrum and boil your plants!

All plants are different, but you can count on your plants wanting warm water over either cool or hot water. Typically, the only plants that enjoy cold water like to be completely submerged in it. You will usually find such plants in most aquariums. On the other hand, hot water is often used to kill bacteria and roots you no longer want in your garden.

Dangers of Watering With Too-Hot Water

While using hot water to water your plants is not a terrible thing to do per se — if you don’t do it regularly, that is  —  it is not recommended. The situation also depends on the temperature of the water, that is, how hot it is and how often you do it. This is because most growing plants can tolerate a couple of minutes of hot watering.

Still, using water that’s over 90 degrees Fahrenheit (32.22 degrees Celsius) to water your plants will most likely cause the leaves to start wilting since they lose their turgidity. Furthermore, anything higher than 100 degrees Fahrenheit (37.78 degrees Celsius) or closer to boiling may kill the roots, cook the cell walls (essentially killing the plants), and destroy any microorganisms living in the soil.

Many gardeners may opt to use boiling water instead of weed killers or insecticides in their garden. Afterall, it is a natural way to get rid of things that don’t need to be there in the first place. However, when you use this method to eradicate weeds, it also kills the other plants in the garden. Any avid gardener is most likely aware of this. 

Observing Changes in Your Plant Post-Watering

If you normally test the temperature of water on the back of your hand, you may need to calibrate yourself to what “warm” or “room temperature” means for plants.

You can purchase a water thermometer if you suspect the temperature of your water has been affecting your plants. However, if you don’t have a thermometer, you’ll have to go with your gut.

Water that’s ice-cold when it hits your skin is most likely too cool. On the other hand, water that burns you is too hot. Try to keep the water at a comfortable temperature; one you would feel too cool showering in but one that doesn’t make your hands feel too cold to move.

Afterward, look for any changes in your plants. If they seem to be freezing or the ground soil looks like it’s compacting, your water is probably too cold. Wilting leaves mean you’re using water that’s too warm.

Does Warm Water Damage Plants?

If you’re worried that your watering temperature affects your plants, look for the signs that point to this.

Warm water doesn’t damage plants. However, you need to make sure your water is “warm” rather than “hot.” This is because hot water can affect the plant and damage the microorganisms in the soil. To prevent this from happening, make sure the water you are using is either lukewarm or cool.

If you notice your plants’ leaves are wilting, then know that you’re using hot water instead of warm water.

Should You Water Your Plants With Cold Water?

Cold water and cool water are different things altogether. Ice cold water shocks even our own hands and is most suitable for use on a hot day. Cool water, on the other hand, is still comfortable to put your hands in.

You should avoid watering your plants with cold water, especially if it’s ice cold. Cold water tends to shock roots and damage plants. However, a temperature that’s medium cool to warm is not likely to cause any problems.

To reiterate, warm water is what is appropriate for watering plants. The ideal temperature lies somewhere between 62 degrees Fahrenheit and 72 degrees Fahrenheit (16.67 to 22.22 degrees Celsius). Still, depending on the definition, this might be cool to some and warm to others.

Final Thoughts

Finding the perfect watering temperature for your plants should be the goal of any serious gardener. Most plants don’t grow well in the winter, which means cold water is unsuitable for most plants. Additionally, hot water can ruin roots and burn the soil.

As you can see, warm water is your best bet — even if you think the heat might mean your plants need to be quenched with cool water.

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AskthePlantician

Hi I'm Mike, a self-proclaimed plantician (an invented profession to describe a plant enthusiast). Based in Sydney Australia, I enjoy the great outdoors and the greenery things around the garden, in particular, indoor climbing plants.

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