Using Coffee Grounds & Cooking Water on Houseplants

Coffee Grounds: Proceed with Caution

Grounds are great for outdoor compost, but indoors they can harbor fungi as they decompose, potentially harming plants. A thick layer also keeps soil too wet. If used indoors, apply very sparingly, only when soil is dry, and avoid acid‑sensitive plants like African violets. They do slightly acidify soil, which may benefit gardenias or azaleas.

Cooking Water: Safe in Moderation

Cooled, unsalted vegetable cooking water is fine for houseplants. Use sparingly. Salty water burns roots.