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Using Rice Water on Plants: Does the Growth Hack Work?

Gardeners say using leftover rice water for plants helps their indoor jungle thrive. Here's what the science says about the growth hack.

Written by
Asha Swann

Rice is super versatile: It's a staple in countless dishes, pairs well with almost any seasoning, and can be eaten by both plant-based folks and meat-lovers alike. And because it's full of vitamins and nutrients, it's no wonder people have even been using rice water for hair growth—it's been shown to result in fuller, thicker strands.

Using rice water for your hair is just one way to cut down on water waste. Another way is using your rice water to feed your houseplants. According to TikTok user Christine Lan, rice water releases nutrients that are great for plants, even promoting beneficial bacteria in plant roots.

However, is this really a hack worth trying? Let's get to the bottom of it.

Rice Water for Plants: Does It Really Work?

Reusing water whenever possible never a bad idea. According to a past study, the global water demand is predicted to increase by 55% by 2050. Why? Because climate change and an increasing global population are impacting our access to clean water.

According to Lan, rice water "holds a mild fertilizer and promotes beneficial bacteria in the roots of plants." So is it true that using rice water for plants is a good idea?

Studies have shown rinsing rice can extract nutrients from the rice. Specifically, rice can lose approximately 7% protein, 30% crude fiber, 59% thiamine, and 26% riboflavin—and that's just a small portion of the nutrients extracted. While washing rice takes nutrients away from the rice itself, it does fill that water with those nutrients.

While there's little research on the effect rice water has on plants, there's one conclusion we can draw: It depends on the plant.

One 2016 study found that when used on garlic plants, rice water helped the plants grow fuller and bigger. This is because rice water is full of starch: the cloudier the water, the more starch it holds. A main component of starch is nitrogen, which attracts the naturally-occurring bacteria in the soil.

The bacteria then turns the nitrogen into nitrate—a natural chemical that helps the process of photosynthesis, starting from the root. In short, rice water can help your plant grow because the roots are healthy and ready to grow.

But it's not always this simple. Not all plants will want extra nitrate, and some plants may not have soil with the right kind of bacteria. Many types of orchids, for example, have fewer microbes than other plants. This means that using rice water on your orchids could introduce too much bacteria with nowhere to go, meaning you could end up with root rot.

Does Rice Water Help Your Plant's Soil?

If you've ever wondered why some plants grow better in certain types of soil, it's likely because of the pH level.

PH measures the amount of acidity in the soil. Nitrates from rice water will raise the acidity, meaning it can be toxic for some plants, but beneficial for others. If you bought standard potting soil, it likely has a standard pH. However, if you bought specialty soil, the pH may be more acidic or more alkaline (nonacidic).

But rice water isn't just high in nitrogen; it also contains protein, potassium, phosphorus, iron, and zinc, according to a 2016 study by the Faculty of Agriculture at the Universitas Riau, Indonesia. This study shows that when used on peppers—a plant that grows best in slightly acidic soil—the rice water made bigger leaves with larger peppers after five weeks.

Different types of rice can have different levels of starch, so it can be tricky to measure what will be right for you and your plants.

Right now the data on rice water for plants is limited. But overall, it seems to be helpful for plants in average potting soil! And if there's one thing that's for certain, it's that reusing rice water is a great way to reduce your water footprint.