Distilled water is good for plants that react badly to tap water, and neutral for everything else. It carries no chlorine, no fluoride, no hardness minerals and no sodium, which removes the usual suspects behind crispy leaf tips. What it also carries is no nutrition at all, so anything watered with it depends entirely on what is in the soil and the feed.
The plants that genuinely benefit
Carnivorous plants such as venus flytraps, sundews and pitcher plants are adapted to nutrient-poor bog water and are damaged by dissolved minerals, so distilled or rainwater is standard practice with them. Prayer plants, calatheas, marantas, dracaenas and spider plants brown at the tips on chlorinated or fluoridated tap water. Orchids and many ferns do better on low mineral water too. For those, distilled water is not a luxury, it is the difference between a healthy plant and a permanently marked one.
Why softened water is the real problem to avoid
If your house has an ion exchange softener, do not water plants from a treated tap. The USGS describes hardness as dissolved calcium and magnesium, and a softener exchanges exactly those for sodium. Sodium builds up in potting mix, damages soil structure and eventually harms roots. Most installers leave an untreated outside faucet precisely for irrigation, and that tap is a better source than the kitchen. Where none exists, collected rainwater or distilled water solves it.
You must feed if you distill
Tap water supplies a trickle of calcium, magnesium and other elements that plants happily use. Distilled water supplies none. In an inert or exhausted potting mix that shows up as pale growth and weak stems within a season, and gardeners then blame the water for a nutrition problem they created. Use a complete fertilizer including calcium and magnesium on a regular schedule, or alternate distilled with collected rainwater, which carries a little more than nothing.
The cheaper answers first
For a windowsill of common houseplants, ordinary tap water left standing overnight, which lets chlorine dissipate, is usually fine and free. Rainwater in a covered barrel is better still and costs nothing but a downpipe diverter. Distilled water bought by the jug for a large collection gets expensive fast, and a home distiller is slow. Reserve it for the sensitive species and the seedlings, and water the rest from the outside tap. Our water softener installation guide explains why that untreated bypass matters.
Questions people ask about is distilled water good for plants
Is distilled water better than tap water for houseplants?
For sensitive species yes, because it has no chlorine, fluoride or minerals. For robust common plants, standing tap water is usually just as good.
Can I water plants with softened water?
Avoid it. A softener swaps calcium and magnesium for sodium, and sodium accumulates in potting mix where it damages soil structure and roots.
Does distilled water need fertilizer added?
Yes. It contains no nutrients whatsoever, so plants watered exclusively with it depend entirely on the potting mix and a complete feed.
Is rainwater as good as distilled water for plants?
For most purposes it is better: nearly as low in minerals, free, and it carries a little dissolved nitrogen and trace elements plants can use.