Yes, rice water is good for plants in moderation. The water left after washing rice contains small amounts of nitrogen, phosphorus, potassium, and beneficial bacteria. In a 2022 study in Agronomy, rice water fermented for 3 days helped plants grow about as well as a standard chemical fertilizer. Use it every week or two instead of plain water, and don’t pour it on undiluted, because the starch can crust the soil and attract gnats.
Below, you’ll learn how to make washed, fermented, and boiled rice water for plants, how to apply it, and which plants respond best. If you like kitchen-scrap fertilizers, also see our guide to banana water for plants.
Benefits of Rice Water for Plants
With rice water, plants enjoy various benefits, including:
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Increased plant growth
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Reduced risk of overfertilization
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Nutrient-packed leaves in vegetables
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Boost yield of many crops
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Help good bacterial populations in the soil
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Aids in rooting and propagation
Disadvantages of Rice Water for Your Garden
Although numerous studies justify why rice water is good for plants, if misused and overapplied, it can lead to:
- Leaching of nitrogen ions (in sandy soil)
- Hardening of the soil crust
- Blooming of harmful bacteria and molds
- Attracting starch-feasting pests like ants and gnats
Hence, like with other plant regimens, the trick is to apply with moderation!
Rice Water Uses for Plants
To avoid your hard work going up in smoke, rice water must be properly applied. Each purpose may have a specific application process, including:
As Fertilizer
Rice water as fertilizer is perhaps the well-studied aspect of exploiting this promising plant food. It is not a surprising fact, as washed rice water contains several elements (N, P, K, microminerals, amino acids, and vitamins) that can boost growth. However, before ditching your usual fertilizer, it is important to note that you may only observe this in a few groups of plants rather than the others!
Simply Watering
If you are one of the planet warriors who wish to align with the UN’s sustainability goals, rice water plants! Rather than deliberately spilling it into your sink, put it to good use by splashing it onto your thirsty houseplants!
Flower Booster
Only scanty scientific studies have shown evidence whether rice water on plants can undoubtedly stimulate plant blooming. What is certain is that the dissolved nutrients in the milky white water may help assist in flowering. So have fun and experiment in your own garden laboratory!
Pest Repellent
While fermented bioinsecticides–one of the rice water uses for plants–is still a broad area of study for pesticide scientists to explore, a few plant enthusiasts assure pest-repelling activity. However, fear not in applying this product to your plants. In theory, microbe-assisted aging of rice water and other rice by-products (rice bran) was shown to produce organic acids and phenols–a promising insect-deterring substance!
Root Promoter
Orchids are quite demanding plants to propagate and cultivate. However, with rice water fertilizer, pretreated orchid plants saw a significant increment in terms of shoot length and number!
Microbial Stimulator
While it may sound counter-intuitive, diversifying the microbial population in the soil can also promote growth–thanks to their secreted hormones beneficial for the roots! This is one of the indirect roles of applying rice water in plants. So go ahead and have a try!
How to Make Rice Water for Plants
Many dedicated scientists have already studied various preparations to optimize its use. Learn how to make rice water for plants with the following methods!
Fermented
Fermented rice water for plants is perhaps the most effective soil inoculant as it also contains beneficial bacteria that stimulate growth. To prepare this aged liquid, simply follow the tips below:
- After cooking rice, place a few scoops inside a mason jar and fill it with water just above it. Use distilled water, as chlorine in the tap can kill the microbes.
- Alternatively, washed rice water can be directly fermented without the cooked rice. It will make the final product less thick than the cooked rice.
- Cover the vessel with a cheesecloth and store it in a dark spot for 1-2 weeks. Some gardeners put them in “nature,” such as in the forest or the woods, to harvest the good microbes.
- Some fungi may grow on the surface. If you see black, brown, or orange growth, discard it and start anew. You should only see white mold, which is deemed harmless. Pro tip: fill as many jars as possible and place them in various locations. It may also be helpful to lessen the fermentation to about 3-5 days, just enough for the bacteria to grow.
- After fermentation, filter and dilute the fermented rice broth and water it to plants periodically. Do not apply it in pure form as it can encrust on the soil surface and may attract gnats.
Fermented Rice Water for Plants — Is It Good?
Lactic acid-forming bacteria that ferment the solution may possess growth-inducing hormones that propel plant growth. They also secrete antimicrobial substances that suppress the propagation of other harmful microbes. With that said, start applying fermented rice water to your plants!
Boiled
The idea of boiling may stem from the fact the nutrients are released from the grains, and the proteins are denatured, making them more available. While this may be faster than fermented water, its effects are yet to be validated by science. Still, it is worth trying!
- Mix a :1 ratio of rice in water.
- Boil for 30-45 minutes or until the grains soften. Please do not forget to stir occasionally.
- Strain the grains to separate the rice water extract using a cheesecloth or a strainer.
- The resulting liquid is starchy and thick. Before applying, cool it down and thin it by adding water. If applied directly, it may accumulate in the topsoil and harden it like a stone.
Washed
Considered to be the easiest and fastest, saving the whitish residue after washing the grains and applying it later is a method with less risk of forming a starchy, crisp soil layer. If you decide to do so, follow the tips below:
- Simply wash the rice with water, ideally with a 3:1 water-to-grain ratio. You can also increase the amount of water to make a less concentrated solution.
- Soak it for about 30-45 minutes. Alternatively, rubbing the grains within your palms also helps extract the nutrients rapidly.
- Extract the liquid using a strainer.
- Store the liquid in a glass jar or a spray bottle. It can be left in a container without refrigeration for about 3 days, but it is still best to cool it. Shake well before spraying to resuspend the colloidal particles in the water.
Methods of Applying Rice Water to Your Plants
Now that we have tackled how to make rice water for plants let’s delve into the different modes of how it can be applied!
Misting
If not the easiest, misting is the most convenient way to apply rice water in plants. Simply take a hand spray and mist it daily for your houseplants. Dissolved nutrients can be directly absorbed through the foliage. It is also a suitable application procedure in epiphytic plants like orchids, which absorb both water and nutrients in the leaves and their aerial roots.
Bottom Watering
If you have succulents or smaller plants, administering your greenie’s regular dose of rice water is best applied at the bottom. Once the pot seems bone dry or slightly moist, simply dip the entire container (or half of it) in a bucket filled with the starchy mixture. Bubbles will stop forming when you completely submerge the pot with water, while the half-filled container will have less liquid after the medium has sponged in the amount it needs.
Drenching
Also called top watering or drenching, watering plants with rice water over the soil surface is a practical approach for gigantic shrubs or trees indoors unless you want to break your spine for lifting such hulking plants. Simply pour the amount you want until you see the excess water running through the holes. This way, the water is evenly distributed to the root system.
How Often to Use Rice Water on Plants
If you are wondering how often to use rice water on plants, the exact figure is not really established. A recent study conducted by Abba Nabayi, Christopher Boon Sung Teh, Ali Kee Zuan Tan, and Ngai Paing Tan recommends applying fermented rice water during watering time. However, as each homemade formulation may vary in viscosity due to the starch content (especially the boiled preparation), you will know when to cut back the application–once the topsoil appears coagulated. It can block the soil gas exchange that favors the growth of anaerobic bacteria and fungi, eventually causing root diseases.
What Plants Like Rice Water
Theoretically, most plants would benefit from rice water. However, since only a few were scientifically tested, knowing the plants that have been demonstrated to show promising results, such as the following, will give you an idea of how to apply it to its relative correctly:
- Mustard — In a study conducted in Indonesia, drenching rice water with mustard plants yielded surprising results: plants were taller, had larger leaves, and had heavier biomass. For best results, apply weekly during the growth season.
- Tomato — If you need to ask what plants like water, our definite answer would be this ruby fruit! As shown in various field and greenhouse trials, tomato plants watered with starchy rice extract grew taller and bore plumper and heavier fruits compared to the plants that received distilled water.
- Eggplant — To maximize the yield, water your eggplants with at least 750 mL of rice water when the soil appears dry. However, there is still a need to supplement your plant with additional plant food such as from compost or earthworm castings.
- Chinese Flowering Cabbage - Asian vegetables like Chinese flowering cabbage will perform well by watering a 3:1 water-to-rice ratio (unfermented rice water). Leaves will expand and store more nutrients–thanks to various growth-promoting bacterium and nutrient-enhancing properties of rice water.
- Desert rose — One of the spectacular flowering succulents, desert rose or Adenium, can be induced to bloom by the periodic splashing of rice water. As they are not heavy feeders, the light mix of nutrients is just enough to boost the plant’s growth. Just do not forget to allow the soil to completely dry out before watering to avoid rotting.
- Orchids — Known to directly snatch nutrients and water using its leaves and hygroscopic roots, this aerial plant will surely benefit from regular misting or rice water. However, if white starchy deposits accumulate on leaves, be sure to wipe them off to keep them photosynthesizing.
- Mushrooms — While mushrooms are not plants, they are quite happy with rice water. Oyster and shiitake mushrooms can yield the best quality and quantity if grown in a concentrated solution of rice wastewater and agar (a medium to culture mushrooms).
FAQ
What does rice water do for plants?
Rice water gives plants a light dose of nitrogen, phosphorus, potassium, and beneficial soil bacteria. In a 2022 study, plants watered with fresh rice water grew about 20% more than plants given tap water.
How do you make rice water for plants?
To make rice water for plants, rinse 1 cup of uncooked rice in 3 cups of water and strain the cloudy liquid into a jar. Use the rice water within 2–3 days, or ferment it for more nutrients.
How do you make fermented rice water for plants?
To make fermented rice water, leave washed rice water in a loosely covered jar at room temperature for 3 days. Beneficial bacteria peak at about 3 days, so longer fermentation isn’t better. Dilute fermented rice water with plain water before use.
How often should you use rice water on plants?
Use rice water on plants every 1–2 weeks, in place of a regular watering. Using rice water more often can crust the soil, attract fungus gnats, and wash nitrogen out of sandy soil.
Is rice water better than fertilizer?
Rice water is not better than fertilizer, but fermented rice water comes close. In one study, 3-day fermented rice water matched a standard NPK fertilizer for leafy vegetables. Plain rice water works best as a mild supplement.
Which plants like rice water?
Plants that like rice water include leafy greens, mustard, lettuce, tomatoes, and eggplants, which all grew better with rice water in studies. Orchids and desert roses also respond well. Succulents prefer dry soil and should get rice water only rarely.
Is rice water good for orchids?
Rice water is good for orchids when diluted and used once or twice a month. Pour the rice water through the potting mix, and wipe any white starch residue off the leaves.
Can rice water kill plants?
Rice water rarely kills plants, but overuse can cause root rot. Too much starch crusts the soil and blocks air from reaching the roots. Always dilute boiled or fermented rice water and let the soil dry between waterings.
How long does rice water last?
Rice water lasts 2–3 days at room temperature or up to 1 week in the fridge. Throw rice water out if it smells rotten or grows black, green, or orange mold. A mildly sour smell is normal for fermented rice water.
