Using rice water for orchids is one of those do-it-yourself tips that has been passed down for generations. But when someone asks what is in rice water or how it promotes the growth of orchids, no one has a concrete answer. So we started looking, and exactly howat the article about garlic water, we were pleasantly surprised by the results.
Rice water is good for orchids because it:
- is rich in starch, which is attractive to beneficial fungi in the orchid soil
- supplies the orchid with protein, free amino acids, calcium, phosphorus, iron, zinc, potassium, thiamine, riboflavin and niacin
- promotes the growth of healthy orchid leaves and stronger, larger orchid roots.
The NPK ratio of rice water and its effect on orchids
Rice water contains mainly rice particles, but also other minerals that have been added to the rice plantation. Half of the water-soluble minerals are transferred from the rice into the water. In a study by Malakar and Banarjee (1959), it was reported that after rinsing the rice, the nutrients it released into the water looked something like this: 7% protein, 30% crude fiber, 15% free amino acids, 25% calcium (Ca) , 47% phosphorus (P), 47% iron (Fe), 11% zinc (Zn), 41% potassium (K), 59% thiamine, 26 % riboflavin and 60% niacin.
The authors justify the lack of an exact NPK ratio by saying that it depends on what rice you use, how much water you use, and how long the rice sits in that water. Basically, there are still no studies that prove the NPK concentration in rice water.
How to make rice water for orchids: recipe
There are essentially two different ways you can make rice water for orchids.
For one thing, you can soak the rice in water, just like you do to rinse it before cooking. The second option is to use double the amount of water and boil it with the rice for a few minutes and then strain the water. However, this second method takes too long.
So back to the first method: you need to rinse the rice in water and swish it around for a few minutes to clean the rice grains. What's left in the water is what you'll use for your orchids.
There is another method, but it poses a great risk of root rot in orchids. It is fermented rice water. The recipe is the same, only the time during which the rice stands in water in a shady, cool place is increased to 3-4 days. Some authors even speak of 10 days. This allows fungi to grow in the water and feed on the rice, turning the water into a fermented solution.
According to a 2021 study(1)Fermented rice water had higher nutrient concentrations (compared to non-fermented rice water), especially N, P and K at 59.7, 60.2 and 25.0%, respectively, indicating the presence of beneficial microorganisms such as Bacillus velezensis, Klebsiella pneumoniae and a variety of Enterobacter spp. which are N-fixing and P- and K-solubilizing bacteria.
Rice water supplies the orchid's mycorrhizal fungi with nutrients
It has long been known thatOrchids in a symbiosisLive with certain fungi called mycorrhiza. Mycorrhiza comes from Greek: “Mykos” means mushroom and “riza” means roots. The fungus supplies the roots with all the nutrients that they cannot digest themselves. Rice water provides this fungus with a healthy amount of starch in the form of carbohydrates, which it eats up.
In summary, the rice water provides the fungus in the orchid pot with the sugars and starches it needs and nourishes it. In return, the fungus breaks down the elements in the potting soil and converts them into nutrients that can be easily absorbed by the orchid roots, allowing the orchid to use less energy.
The breakdown of the starch that the rice water provides is used to generate energy for your orchid. The mushrooms that receive this starchy water from the pre-rinsed rice increase the amount of CO2 in the orchid pot along with additional doses of nitrogen, phosphorus and potassium. This promotes their growth.
According to a study (2) by Dr. Christopher Teh (expert in plant modeling, environmental biophysics and soil conservation), lecturer at the Faculty of Agriculture, University of Putra Malaysia, rice water contains nutrients that could complement conventional fertilizers. It has been reported to increase the growth of many plants, from above-ground to below-ground biomass.
White or brown rice: which is better?
Only a few studies (2) compared the effects of white (WR) and brown rice (BR) water on plant growth. Purnami et al. (2014) evaluated the use of WR and BR water on the growth of Phalaenopsis orchids and found that using BR water once every four days increased root length, plant height and biomass significantly more than WR water .
Can you swap your orchid fertilizer for rice water?
It is not recommended to completely replace rice water with chemically produced fertilizer as your orchid needs other micronutrients that rice water does not provide. It's good to make a schedule of when to fertilize your orchids and keep the dosage between the recommended levels. For rice water, we don't know exactly what these dosages are. You could quickly overdose on a micronutrient. We recommend not using rice water more than once a month and maintaining the normal fertilization schedule with the recommended NPK ratio of 20-2-20.
1.Agronomy 2021; Chemical and Microbial Characterization of Washed Rice Water Waste to Assess Its Potential as Plant Fertilizer and for Increasing Soil Health
2.Pertanika j. Sci. & Technol (2021);Wastewater from Washed Rice Water as Plant Nutrient Source: Current Understanding and Knowledge Gaps
