When caring for a plant indoors, the goal is to recreate the conditions it would find out in nature. You can place it close to a window to give it natural sunlight, aerate its soil to mimic the movement of worms, or put a pole behind it if it tends to climb up trees. But what about water? Since tap water contains more salt and minerals than pure rainwater, you might be wondering if it’s the best thing to be feeding thirsty houseplants.
Here, plant care experts explain when tap water is A-OK, and when you might want to swap it out for something else.
Why tap water can harm certain plants.
Overall, if you have clean, high-quality tap water, you should be fine giving it to all of your plants, explains Erin Marino, the editorial lead at NYC-based shop The Sill. She’s based in New York City and hasn’t run into any problems through the years of watering her plants straight from the tap.
If you live in an area with hard tap water that tastes of minerals, though, some of your plants might respond poorly to it. Marino gives birds of paradise, calatheas, and peace lilies as examples. “These are plants that have more of a sensitivity to the salt and minerals that are found in tap water,” she tells mbg.
When you water these plants with hard tap water, some of those excess minerals are left behind. Over time, they can increase the salt content in your plant’s soil, which can disrupt some of its natural processes and cause imbalances. Dehydration, slow growth, and even root rot can follow.
A few signs that your plant is suffering from excess minerals, like brown spots on leaves and wilting, are also symptoms of overfertilizing or underwatering, which can make this problem tricky to diagnose. If your plant’s pot is covered in a chalky white residue, that could also be a signal that too many salts have collected in its soil.
If you notice that some or all of your plants are consistently showing these signs of mineral buildup, plant expert and chemistry teacher Paul Thompson, M.A., recommends switching your water source to see if it helps.
Before you do, flush out the plant with lots of distilled water to wash away some of those excess salts. From there, you can alternate between watering them with tap water some days and a cleaner water source on others.
Marino says it’s important to continue to give your plants tap water sometimes, even if it’s hard, because “the tap water has all these minerals, and some of them are nutrients for the plants. Distilled water is chemically inactive and has no minerals, so your plant might not be getting all the resources it needs in an indoor environment.”
Plants cycle through over a dozen other nutrients to stay healthy, including some that are found in tap water, like calcium and magnesium. In nature, these can come from organic matter like decaying leaves and animal waste. At home, you’ll need to provide them yourself.
Switching off between tap and another water source can help ensure that your plant is getting the minerals it needs at the levels it can handle. Marino and Thompson say any of the following water sources can work for days when you’re not using the tap:
As always, water your plant with room temperature water until you see a stream start to flow through its drainage hole. And don’t forget to feel your plant’s soil before watering to make sure it actually needs the soak (overwatering can be just as detrimental as underwatering!).
Some houseplants respond poorly to hard tap water that’s high in minerals. If your bird of paradise, calathea, or peace lily has browning or wilted leaves, try watering it with a purer water source like rainwater or distilled water every once in a while and see if it helps the problem go away.
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