Using the right water is a must when growing indoor plants. It transports nutrients, helps generate oxygen, and provides necessary thermoregulation to a plant. 

To optimize your routine, you need to consider water quality, pH level and whether it’s soft or hard. 

What are pH levels?

The pH level shows the level of acidity. Soil pH can be acidic, neutral, and alkaline, and most indoor plants prefer a slightly acidic or neutral pH. Plants that prefer an acidic pH are azalea, hortensia, maranta, and some aroids. Plants that prefer an alkaline pH are myrtle, desert rose, and lavender.

Acidity depends on the water quality, fertilizers, and soil pH. To make the soil more acidic, you can use hydroponic or fish tank solutions, add citric or oxalic acids, or infuse the water with bog peat. Hard water creates alkaline conditions.  

What is water hardness? 

Water hardness depends on the quantity of calcium and magnesium salts in it. It can cause an acid-alkaline imbalance in the soil and lead to a lack of micro- and macroelements. As a result, the upper and lower leaves turn pale or yellowish, and their veins can become brighter than the leaf color. You might also notice a white salt coating on the surface of the leaves, which is another sign of the imbalance. 

Is tap water a good choice for your houseplants? 

When it comes to choosing water for houseplants, try not to use it directly from the tap. It contains substances like chlorine and fluoride that can build up and be harmful to your green friends. Before using tap water, leave it in a container in the sun for a day or two. This allows any chemicals to evaporate. It can also contain mineral additives, so consider using less fertilizer if watering your plants from the tap. Showering your plants every few months can help rinse off the excess salts and minerals caused by tap water.

Using distilled water for plants

Is distilled water good for plants? Distillation removes minerals and chemicals, improving water quality. Distilled water is soft water without the trace amounts of sodium left by a mechanical softener. Using distilled water for indoor plants provides a safe and impurity-free source of irrigation that can prevent any toxicity from chemical or mineral buildup. It’s also free of contaminants like bacteria. 

If you want to start using distilled water for your plants, you can purchase it at most grocery stores or make your own with a distillation kit. Kits can be found in sporting goods departments or you can create your own contraption with common household items.

Is rainwater good for plants?

Rainwater is naturally soft and free of many salts, minerals, and chemicals. You can use it for growing indoor plants without causing build-up on leaves and soil. It’s also slightly acidic, helping to balance the soil’s pH. And it contains nitrates that act like fertilizer. 

In big cities, rainwater can be acidic because of acid rain. It can also contain soot and toxic chemicals that worsen water quality. Try not to use rainwater after an extensive period of drought, and wait 20-30 minutes after the rain has started to begin collecting it. 

How to Reduce Water Hardness Effectively 

  • Preparing meltwater


Meltwater for plants

First, freeze tap water. Once it solidifies, defrost it and let it reach room temperature. You’ll see some sediment. Remove it, and vóila! Water is ready to be applied to your growing houseplants. 

  • Installing reverse osmosis filter systems


Filtered water

This is the most efficient way to reduce water hardness. Filtered water is safe, because it’s free from sediment, bacteria, sulfates, nitrates, etc. 

  • Using fish tank water for plants


Fish tank

Even though it might look cloudy or dirty, aquarium water is rich in nutrients. So, applying it to your plants can also fertilize the soil. 

Ineffective ways to reduce water hardness

  • Boiling water

Technically, boiled water is less hard. However, it is not suitable for houseplants because it is poor in oxygen and nutrients. 

  • Leaving water to settle

Despite its popularity, this method is ineffective at changing water hardness. Settled water doesn’t contain less salt, but it does release any chlorine or flouride and reach room temperature – which is better for your plants.  

What Water to Choose for Plants

When it comes to choosing the best water for plants, it’s best to use rainwater or meltwater. In terms of quality, they are both safe, soft options that are rich in oxygen and have a slightly acidic or neutral pH that’s suitable for many growing houseplants. 

When it comes to carnivorous plants, they need soft, impurity-free water with a little salt. Opt for distilled water or water filtered through a reverse osmosis system.