Using Rice Water To Fertilize Houseplants? Avoid This Mistake That Could Cost You Your Plant

Washing rice before you cook with it is important, but it begs the question of what to do with all that leftover starchy water besides just pouring it down the drain? You can feed your houseplants with it, though not for the reasons you may think. Rice water doesn't have any additional nutrients that plants need to grow — for example, the nitrogen, potassium, and phosphorus found in conventional fertilizers — and the starchy residue doesn't necessarily "fertilize" your plant. However, it is still water that would otherwise just be dumped down the sink, so if you're not saving your rice water for cooking, you might as well use it to hydrate your plants — even if it doesn't come with any fertilizing benefits.

The important thing to make sure of is that you're using unseasoned and unsalted rice water, as salts, fats, and food residue can damage plants. Don't make that mistake. Also, only use rice water once a month on your plants, as the residual starches in the water can attract pesky fungi or bacteria. The starch can also ferment, which may encourage unhelpful bacteria to take up residence on your favorite houseplant.

Several users have taken to Reddit to share other important concerns about watering plants with leftover starchy water. One individual residing in a humid climate noticed that their soil got moldy after they applied leftover rice water. Another suggested combating potentially moldy soil with cinnamon. The spice is also a known deterrent for critters like mice, though some plants may be sensitive to its compounds and it should definitely be used sparingly on delicate plants.

Another suggested that, when trying this hack, you shouldn't let the water sit for too long. "In fact I keep a watering can by the sink to fill with any rinsing water. Just make sure to use it relatively soon otherwise it starts to ferment and gets stinky," they said. Others offer creative suggestions for using that leftover starchy water, including for feeding a sourdough starter. "You can also use it to wash your hair, wash your sink (the starch is supposed to scrub but not scratch), wash your face, and soak containers that have strong smells (like kimchi)," one Redditor said. 

But if you're still looking to fertilize your houseplants on the cheap, then maybe try using a solution made from oats and tea instead of rice, but you'll still need to keep an eye out for any possible mold.