What Water is Good for Indoor Plants? 11 Frequent Questions

In regard to questions about what water is good and safe for plants, there are many tips, opinions, and recommendations around. In this post, you will find the answers to all frequent questions about what water is good for your houseplants.

Good water for indoor plants is rainwater, distilled water, or filtered tap water. These water types contain high levels of dissolved oxygen as well as of all major plant nutrients such as nitrogen, phosphorus, potassium, calcium, and magnesium while levels of toxins such as chlorine or fluoride remain low.

There are plenty of extra tips for each question to make sure you don’t only find answers to your question, but also learn how to improve the water you use for your plants. Let’s dive right into it and learn more about what water is good for your houseplants!

Is Tap Water OK for Plants?

Generally, if the tap water of a living area is drinkable for humans, it is OK for plants as well.

Still, highly sensitive plants may struggle with regular tap water and there are many simple ways to improve it for better quality plant water. Tap water usually contains treated chemicals such as chlorine or fluoride which in low quantities do not damage plants, but are certainly better avoided for plant water.

Filtering tap water is an excellent and easy way to improve tap water quality. These are the most common practices to filter tap water:

  • Use a filter pitcher: Buy yourself a filter pitcher (such as from BRITA or other brands).
  • Add a faucet attachment in your kitchen: Install a filter faucet in your kitchen. This works great but involves some initial costs.
  • Let tap water sit for 1-5 days: Fill your watering can with tap water and let it sit for 1-5 days. Heavy metals will sink to the bottom of the can. Make sure you don’t stir the water before using it and only use the top 2/3 of the water, pour the rest down the sink.
  • Use meltwater: Freeze tap water and then let it melt in a container. There will be some sediments at the bottom, filter these out before using the water for your plants. In my opinion, this is the least effective method, but as it makes tap water a little better I still wanted to mention it here.

How to Know If My Tap Water Is Safe for Plants?

Safe tap water for plants needs to meet certain requirements as to the levels of its components. The following specifications are important:

  • Hardness/softness of water: Water hardness levels of 30 – 60 ppm are considered ideal for plants.
  • Acidity/Alkalinity of water (=pH level): pH levels of 5.0 – 7.0 are considered ideal for plants.
  • Chlorine level of water: A chlorine level of 50 ppm at the max doesn’t harm plants.
  • Fluoride level of water: The fluoride level should be 1 ppm at the max. Higher amounts will damage plants.

To find out exactly what levels of each component your tap water has, check out the local authorities’ official data on tap water or get it tested in a laboratory.

Is Chlorine Safe for Houseplants?

Chlorine is not per se damaging to plants, though if present in high amounts, it builds up in the soil and can inhibit foliage growth.

In plant water, a chlorine level of 50 ppm at the max is considered safe for plants.

Is Fluoride Safe for Houseplants?

Contrary to chlorine, fluoride causes damage to plants already in very low amounts and is best avoided in plant water.

According to WHO regulations, regular tap water contains 0.5 – 1 ppm of fluoride. For plants, fluoride should not exceed 1 ppm at the max while less is always better.

What Houseplants Are Sensitive to Tap Water?

It is true that some plants are more sensitive to regular tap water than other, less picky plants. Among the most common sensitive houseplants are the following plant species:

  • Spider plant (Chlorophytum comosum)
  • Red-veined prayer plant (Maranta leuconeura)
  • Zebra plant (Calathea zebrina)
  • Good luck plant (Cordyline terminalis)
  • Peace lily (Spathiphyllum)
  • All Yucca plants (Asparagaceae)

Is Rainwater Good for Plants?

Rainwater is considered to be the best water for indoor plants due to its high nutrient and oxygen levels. It contains all major plant nutrients such as nitrogen, phosphorus, potassium, calcium, magnesium, and sodium as well as occasionally sulfur, and is well endowed with oxygen.

Rainwater is best collected directly in a barrel or tank avoiding any external interferences that cause contaminations. Other methods for rainwater collection are to place jars and open containers in any outside area where it rains on them or to temporarily place indoor plants outside when raining.

Please Note: In city centers or industrial areas, air pollutants can be taken up by rainwater and contaminate it. If you live in such an area, check the local authorities’ data on rainwater quality or get it tested.

Is Distilled Water OK for Plants?

During the distillation process of water, water is vaporized and its condensate is collected in a separate container. By removing all toxins and contaminants through distillation, distilled water is totally clean and therefore well suited for plants.

Distillation not only removes all harmful ingredients from water, it also removes all nutrients which can be considered its only disadvantage. When using distilled water for plants, it always needs to be combined with fertilizer to feed plants adequately.

Tip: Reverse osmosis (RO) water is a good alternative to distilled water, though expensive in its initial outlay as it requires installing a filtration system below the sink. Reverse osmosis filters tap water in a multi-step process to its cleanest state. Unlike distilled water, reverse osmosis adds nutrients and minerals back to the water in the last step of the process which makes it clean and nutritious water.

Is Bottled Water Good for Plants?

Bottled natural or spring water is good for plants as it contains good levels of minerals, nutrients, and oxygen as well as almost no contaminants or toxins. Bear in mind though that buying bottled water for your regular plant care is not a very eco-friendly way of watering your plants.

In the face of increasing planetary plastic pollution, creating further plastic waste is best avoided.

Is Sparkling Water Good for Plants?

Similar to bottled natural water, sparkling water contains good amounts of minerals, nutrients as well as oxygen while levels of toxins or contaminants are near zero.

In contrary to natural bottled water, the carbon dioxide gas (CO2) present in sparkling water gives it higher levels of carbon which makes it more acidic. It is therefore recommended to only use sparkling water as an occasional supplement for plants and not as regularly used plant water.

Is Soda OK for Plants?

While Sodas contain similar components as natural or sparkling water, such as nutrients, minerals, and oxygen, they also contain high amounts of sugar.

Sugar on a regular basis is harmful to the root system of a plant as it damages the root tips and inhibits the proper intake of nutrients. Water high in sugar such as Sodas should only be used on dying plants as a boost for their metabolism. For healthy plants, sugary water or Sodas are best avoided.

What Is The Best Water for Houseplants?

Generally, rainwater is the best water for indoor plants. It has very high nutrient and oxygen levels and usually does not have many toxins which is perfect for plants. In addition, watering plants with collected rainwater comes with no further costs and is a very eco-friendly way compared to other types of water.

The disadvantages of rainwater are that depending on your living area, the quality of rainwater can vary. If you are living right in a polluted city center or in an industrial area, rainwater might contain contaminants which is soaks up through the air.

Another problem can be harvesting rainwater: Do you have any outside space at hand? Can you harvest it directly or does it pass an entire urban roof system until it fills your tank?

Considering your circumstances, the best water specifically for your plants in your living space might rather be distilled or filtered tap water.

There are more alternatives and ways to prepare water that is just as beneficial for your plants as rainwater. Learn all about the best plant water options and how to prepare the best water for your indoor plants in this post: What Water Is Best for Houseplants and 7 Tips to Improve Water

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