Peace Lily (Spathiphyllum)

The peace lily tells you when it needs water — it droops dramatically, you water it, and within hours it perks right back up like nothing happened. It's one of the few low-light houseplants that actually flowers indoors, producing elegant white spathes year-round. It topped NASA's air-purifying list for removing ammonia, benzene, and formaldehyde. The only caveat: it's mildly toxic to pets if ingested.