Is chlorine-treated water harmful to houseplants? In a word, no. Still, many people attest that chlorine-treated water is harmful to plants. This maybe due to the concentration of chlorine early in the morning, when water has been standing all night in the pipes. To be safe, allow the tap to run a few minutes prior to gathering water. Its good to know that chlorine disappears rapidly upon aeration. If you really want to be sure on the safety of water, let the tap water sit overnight in a pail before applying to plants. Nevertheless, fluorine does not go away.
There areplants that exhibit some reaction to fluorine in tap water. In some areas of the country, foliage shows tip burning when the soil or water carries as little as 1/10 ppm of fluorine. Because some municipal water supplies contain as much as ten times this amount (added to reduce tooth decay) the use of rainwater, well water, or water from a defrosted refrigerator is highly encouraged for these plants. Make sure your rainwater is not acidic.
If you suspect that water treated with fluoride is causing problems or if your soil mixture contains