Want to give your houseplants a natural boost, clean them up and make them look their best in just one step? Bring them outside the next time there's a good rainstorm. Since treated tap water can contain mineral deposits that build up over time, fresh rainwater can rinse off those hard deposits. Plus, the dust and debris on the leaves will rinse off. And since tap water can also contain chlorine, a fresh flush of clean rainwater can help them thrive. When it clears up, they'll get a strong dose of bright sunshine (which they love), and it'll dry off the excess water.