Is Distilled Water Good For Plants? It’s Complicated – There’s No Scientific Consensus
Elizabeth is a Permaculture Garden Designer, Sustainability Consultant and Professional Writer, working as an advocate for positive change. She graduated from the University of St. Andrews with an MA in English and Philosophy and obtained a Diploma in Applied Permaculture Design from the Permaculture Association.
Reviewed By ROY NICOL
Roy is a Professional Gardener and Horticultural Consultant, specialising in large garden year-round maintenance and garden development. He is an RHS Master of Horticulture and uses his research in the application of no-dig methods in ornamental garden settings. Roy has been a Professional Gardener for more than six years and is a member of the Chartered Institute of Horticulture, Professional Gardener's Guild and Association of Professional Landscapers (Professional Gardener).
Contributions From DANNY CLARKE
Danny Clarke ('The Black Gardener') is a British Horticulturist and Garden Designer. He is probably best known for his TV presenting roles on the BBC's Instant Gardener, his time on the ITV This Morning team and Filthy Garden SOS aired on Channel 5. He also co-directs CIC Grow 2 Know, a charitable organisation encouraging diversity in horticulture.
Many gardeners overlook one of the most important things for good plant health – fresh water.
Could using distilled water be the answer?
Some people say that using distilled water to water your plants is the best option and sometimes, that may indeed be the case.
However, while using distilled water may sometimes improve plant health and growth in very specific circumstances, it may not always be the best thing.
Which type of water you should use when watering your plants very much depends on where your water comes from and the properties it has.
It also depends on which plants you are growing, and where they are being grown.
Let’s delve a little deeper to help you understand the best options when it comes to watering your plants.
What Is Distilled Water?
Distilled water is water which has been purified by being boiled.
As it boils, the water evaporates.
In the distilling process, this evaporation is condensed on a cold surface and collected to give something that is very close to pure H2O.1Blades, N. (2019, July 17). Distilled Water. WebMD. Retrieved March 14, 2023, from https://www.webmd.com/diet/distilled-water-overview
During this process, impurities such as heavy metals, chemicals like chlorine, parasitic organisms and other contaminants are removed.2Drinking Water Treatment: Distillation. (n.d.). Retrieved March 14, 2023, from https://extensionpublications.unl.edu/assets/html/g1493/build/g1493.htm
However, minerals required for plant growth are also removed and so where plants cannot obtain these from the growing medium instead of the water, plant growth could actually suffer.
There is no scientific consensus on whether distilled water really is better for your plants.
However, some scientists suggest that it could improve plant performance in certain situations.3Alwan, N. T., Shcheklein, S. E., & Ali, O. M. (2021). Evaluation of distilled water quality and production costs from a modified solar still integrated with an outdoor solar water heater. Case Studies in Thermal Engineering, 27, 101216. https://doi.org/10.1016/j.csite.2021.101216
In particular, distilled water is said to be good for some houseplants and other plants grown indoors in containers.
This is because plants grown in containers do not obtain the benefits of natural soil filtration, and chemicals and other contaminants found in tap water are not diluted by natural rainfall, so where tap water is used, this can become more of an issue.
Can You Distill Water At Home?
It is possible to distil your own water at home, using a water distiller that has been purchased for the purpose, or by making a make-shift distiller using a pan, a bowl, a lid and some ice.
However, this is a time-consuming process and you will only ever be able to make a small amount of distilled water at a time.
What’s more, distilling water on a hob is likely not a very sustainable choice.
It requires a lot of energy, which, especially when this energy is not entirely from renewable sources, hardly seems worthwhile.
It may negate the benefits to the environment you gain from growing your plants in the first place.
The other option, of course, is to purchase distilled water, but since distilled water is usually purchased in plastic containers, this also raises thorny issues when it comes to trying to grow in a sustainable and eco-friendly way.4Reasons to Avoid Bottled Water. (2013, November 13). Sustainability at Harvard. Retrieved March 14, 2023, from https://green.harvard.edu/tools-resources/green-tip/reasons-avoid-bottled-water
Understanding Your Water Source
When trying to work out what to use to water your plants, understanding your own water and where it comes from is key.
Sometimes tap water will be perfectly suitable and indeed even better for watering than distilled water because of the minerals it contains.
If possible, you should always seek to understand your tap water, where it comes from and how it might be treated before you use it on any of your plants.
Not all water sources were created equal and some will be much more problematic when watering plants than others.
Is Your Tap Water Harming Your Plants?
We are fortunate here in the UK to have one of the best municipal water supplies in the world.5Water and health. (n.d.). Water UK. Retrieved March 14, 2023, from https://www.water.org.uk/advice-for-customers/water-and-health/
The water coming out of our taps has usually been treated to a high level, and levels of chlorine are much lower than they are in many other countries.
However, the quality of tap water varies greatly from region to region, and impurities can enter your supply even from the individual pipes leading to your home.
From micro-plastic pollution to heavy metals, most tap water will have some impurities in its supplies.
While impurities may be worrying for a range of reasons, many of the plants you grow may have no issues if you have to water with tap water where you live.
Understanding where your water comes from and how it reaches your home is important, since it can help you to understand the properties of that water, and how it might affect your plants.
Some plants are particularly sensitive to the chlorine and other chemicals and impurities that might be present in the water supply to your home.
Some plants may also be sensitive to the low pH, or calcium and magnesium content of the tap water in hard water areas.
“For example, ericaceous plants such as camellias and rhododendrons prefer lower pH water which is free of calcium,” says Master Horticulturist Roy Nicol.
Even if you do not live in a hard water area, tap water isn’t the best thing to use on your plants, regardless of where you live.
It is always better to use natural rainfall where possible to water indoor plants, as well as relying on it for plants growing outdoors.
Is Rainwater Harming Your Plants?
“We’ve got to be less wasteful and even as gardeners, we are guilty of that,” says Danny Clarke, TV Personality & Garden Designer.
“One of the things that I think we can do is conserve running water from the mains, as this can be very wasteful and a lot of it goes to plants that don’t really need it.
“A great way of conserving water is to install water butts in our gardens.”
As Danny says, harvesting rainwater to water your plants is almost always the best solution.
If at all possible, affix water collection vessels to guttering to collect water that falls on roofs, or make ponds or other bodies of water to store water in your garden.6Taylor, A. (2012, April 25). What’s the best way to store rainwater? BBC News. Retrieved March 14, 2023, from https://www.bbc.co.uk/news/magazine-17839818
Think about finding ways to catch rainwater on your property and keep it around.
Even leaving a bucket on a balcony or hanging from a window could help you if you are growing plants indoors.
Rainwater is naturally mildly acidic, which most plants will love.7Water: collecting, storing and re-using. (n.d.). Royal Horticultural Society. Retrieved March 14, 2023, from https://www.rhs.org.uk/garden-jobs/water-collecting-storing-and-using
It contains nitrates and small amounts of organic matter which provides other plant nutrients and it is a free resource that you should be taking advantage of.
“Over time, the water in water butts can start to smell as the organic matter breaks down,” says Roy.
“To counter this, it might be worthwhile to use an organic water butt treatment.”
However, it is important to think about where you live.
In some areas, such as homes below flight paths or in city centres where there is a lot of air pollution from traffic, rainwater will likely not be as pure and natural as you might think it is.8Air pollution. (2017, February 3). Met Office. Retrieved March 14, 2023, from https://www.metoffice.gov.uk/weather/guides/air-quality
It may be contaminated with pollutants of various kinds and may be far more acidic than usual.
“It’s best to avoid using rainwater for seedlings as the possible pathogen content can lead to the fungal problem of damping off,” explains Roy.
Would Your Plants Benefit From Distilled Water?
In most cases, as mentioned above, your container plants will be happiest with rainwater and many can cope fine with tap water where harvesting rainwater is not possible.
However, in a few very specific cases, for particularly fussy plants grown in containers indoors, the neutral pH and purity of distilled water may make for healthier and happier plants.
“As minerals have been removed from distilled water, it’s advisable to supplement these with a balanced organic plant feed,” adds Roy.
Just remember that distilled water is, in the majority of cases, not really required, and most plants will always be happiest with natural rainfall.
