Can You Use Leftover Pasta Water for Plants?
Don’t throw out that pasta water from your penne just yet! Preparing pasta today can feed plants and soil tomorrow.
Pasta water can be used as a mild fertilizer and a sustainable water source for plants due to the abundance of starch and dissolved nutrients. It can be used 1) directly in the soil after cooling, or 2) fermented for 3-12 days in a sealed container to make a mild fertilizer.
All sorts of starchy wastewater from our kitchen, from pasta water, rice water, noodle water, to even potato water can spur a release of nutrients when applied to the soil.
Benefits of Using Pasta Water
Pasta water is the wastewater after the pasta is cooked and boiled. The remaining water is full of dissolved nutrients and starch derived from the pasta which can be used as an alternative watering source for plants.
Upon cooling, the pasta water can be used to water plants, fertilizing the soil and preventing useful water from becoming waste. It’s a simple concept rooted in the sound principle that clean wastewater can still be reused on plants.
1 – Fertilizing the Soil with Starch
Starch is a complex carbohydrate found in many food sources such as rice, potatoes, and wheat (pasta’s main component). The starch-rich pasta water can be used on soil and plants to improve soil microbial activity, soil carbon metabolism, respiratory rate, root viability, and plant energy.
Studies have shown that the presence of starch in soil prompts the release of nutrients by promoting microbial growth in the soil itself. This, in turn, promotes plants by giving them more access to nutrients for metabolism and photosynthesis.
This fertilization process is made more potent with the fermentation of starchy water (hang on, we discuss this later). To be specific, there is a marked increase in Nitrogen (N), Phosphorus (P), Potassium (K), Sulfur (S), Manganese (Mg), Ammonium (NH+4), and Nitrate (NO−3), among others, the longer the fermentation process goes past 3 days.
Starch is commonly expressed as (C6H10O5)n and is broken down in the digestive systems of organisms into glucose. Apart from being a life-sustaining compound, starch also has other uses. Culinary uses such as a thickening agent in baking, confectionery, and ordinary cooking. It’s also used in other industries such as paper manufacturing, mining, textiles, and building materials.
2 – Environmentally Sustainable
Instead of being poured down the drain, pasta wastewater can be used to fertilize the plants and soil.
The average serving of pasta per person is 100 grams and requires 1 liter of water (0.26 gal).
Cooking pasta has a relatively small water footprint – amount of water used – compared to showering (60 liters or 15.85 gal), bathing (80 liters or 21.13 gal), and the majority of other home activities which may reach up to 100 liters (26.41 gal). However, every liter counts when it comes to sustainable living. .
NOTE: While cooking pasta already has a small water footprint, restaurants often reuse the same boiling pasta water to cook more servings of pasta. Chefs claim that it creates a richer more flavorful taste.
Applying Pasta Water on Plants
Cooking pasta in boiling water involves hydration (absorption of water) and gelatinization of starch (the heating of starch compounds). This creates a nutrient-rich wastewater useful for plants
With these two processes, the pasta becomes wet and soft with its renowned supple and viscous texture. The wastewater resulting from these processes becomes seeped in dissolved nutrients and starch.
1 – Direct to Soil
Upon cooling the pasta water for 20-40 minutes until it is at its normal temperature (20-25°C or 68-77°F), the pasta water can be poured over the soil of the desired plant. The pasta water is filled with starch and dissolved nutrients from the pasta.
The presence of starch alone helps in promoting beneficial microbes in the soil near the root which results in better plant growth.
This is the simplest and most direct method. Immediately after having no more use for the boiling pasta water, you can simply leave it out to cool. When cooled, you can either dump it on the closest plant that seems unhealthy or kept in storage for future use.
Fortunately, the pasta water does not have any pungent odors attached to it. Pasta water smells like a mixture of wheat and water. It will not leave any lasting smell on the soil nor will the smell negatively affect plant and soil health.
2 – Fermented Pasta Water
Fermented pasta water can be fermented into a mild fertilizer. Mix the pasta water with 1 spoon of sugar and 70 ml of milk in a sealed container. Allow the solution to ferment for 3-12 days until it turns sour, opaque, and translucent.
Studies have shown that fermented starchy water like pasta water and rice water can significantly affect plant growth and beneficial microbe growth in the soil. The longer the fermentation period, the more potent its effects. However, it is recommended to keep the fermentation period from 3-12 days as studies suggest.
The fermentation method is especially useful if you live in areas where the ground is always wet like in tropical climates that have unpredictable weather patterns. It is also good for households whose main diet consists of pasta or other starchy products.
NOTE: Fermentation often produces a pungent odor. Applying the fermented pasta water can affect the smell of the soil but this will be removed as the soil absorbs it as time passes. Some gardeners add a bit of citrus liquid to their fermented pasta water to reduce or neutralize the odor.
What Nutrients Are In Pasta Water?
The nutrient content in pasta will differ between manufacturers since they all use different recipes in making their own. However, the nutrient variance between dry pasta and fresh pasta is not a concern because starch is the main compound of interest.
A lot of nutrients are actually lost in food during the cooking process. Some are dissolved in the pasta water due to heat and pressure. What nutrients are in the pasta water are just bonuses to the starch that is the main compound we are after.
1 – Nutrients in Dry Pasta
It is produced by mixing wheat and water without eggs which are later molded and dried. Apart from starch, dry pasta has calcium, iron, and potassium.
Dry pasta is the most common type of pasta for households due to its ease of access, use, and convenience. Dry pasta is ubiquitous in almost any household and comes in a variety of shapes and sizes such as spaghetti, penne, lasagna, or macaroni, among others.
The nutritional value of whole-wheat dry pasta is as follows:
Dry Pasta, whole-wheat (100 g serving)
2 – Nutrients in Fresh Pasta
Fresh pasta is made with wheat flour and eggs and does not undergo any drying process. It has more nutrients such as iron, sodium, vitamins, and other minerals due to the presence of eggs.
Fresh pasta is less accessible than dry pasta because they are handmade, unlike dry pasta which is a more common commercial product. Fresh pasta is often produced in a manual and traditional manner. Hence, it’s more common to find fresh pasta in authentic Italian restaurants or traditional Italian homes.
The nutritional value of fresh pasta is as follows:
|Fresh Pasta (100 g serving)||Amount|
Other Sources of Starchy Water
Starch is an important compound for organic life since it provides much-needed energy to sustain metabolic functions. It can be found in many of our culinary products such as 1) rice, 2) dried noodles, and 3) potatoes. The wastewater serves as a water source and mild fertilizer much like pasta water.
The above are all starch-rich foods. Furthermore, their preparation involves the use of water which means we can use the starch-rich water directly or ferment it for our plants. You may even mix your all starchy wastewater together to maximize.
1 – Rice Water
Rice water can act as an alternative water source or mild fertilizer for plants. Since rice is often rinsed multiple times before cooking, the accumulated wastewater is rich in starch that is beneficial to soil and plant health.
The chalky powder on rice is the scratched-off starch that results from rice grains rubbing against each other during milling and transportation. Rice is often rinsed multiple times with water before being cooked and the milky rice water is rich in starch.
The rice water can either be used 1) direct-to-soil or 2) fermented. Fermenting the rice water only requires that the water be placed in a sealed container for 3 or more days. Additives such as sugar or milk can be added to make a more potent solution.
Studies have shown that fermenting the rice water for at least 3 days can positively affect plant growth and microbial growth in the soil.
NOTE: However, unlike pasta water, the rice water is not boiled. The rice water results from the cleaning of the rice before it is finally cooked by letting it sit in the boiling water. The actual water used to cook the rice during the boiling process is completely absorbed by the rice grains to bring out its fluffy texture.
2 – Dried Noodles
The cloudy noodle water is rich in starch and other nutrients that have mixed with the water during the boiling process. Such water is beneficial for plants growth.
This works with the same principle as pasta water. The pasta water can be used 1) direct-to-soil or 2) fermented. Again fermenting works by placing the starchy water in a sealed container for 3 or more days. Mixing additives such as milk or sugar can make for a more potent mix since it aids the fermentation process.
3 – Potato Water
Potato water is likewise rich in starch, vitamins, Iron (Fe), Calcium (Ca), and Potassium (K), among other nutrients. These nutrients valuable for plant growth, are either dissolved or leached in the boiling water.
Similar to pasta water, it can be used 1) direct-to-soil or 2) fermented. The procedures and principles are the same. Though the starchiness is less noticeable, the potato water is rich in it and other nutrients. Potato skin is particularly rich in vitamins and minerals so boiling unpeeled potatoes will definitely result in more
Things To Avoid in Using Starchy Water
There are a few things to avoid when using either pasta, rice, noodle, or potato water. The two things to remember are 1) to not use yeast, 2) to not use boiling water, 3) to not apply starchy water after fertilizer has been applied, 4) to not use salt, and 5) to not ferment for more than 12 days.
These things might seem like common sense but it’s important to remember them since it’s often the small things that doom us. A bit of caution and common sense can go a long way.
1 – Do Not Use Yeast
Adding yeast (Saccharomyces cerevisia) into the starchy water will induce alcoholic fermentation that converts sugars into ethyl alcohol and carbon dioxide. Alcohol in the soil or on the plants negatively stunts plant growth and development.
The alcoholic fermentation induced by yeast is not wanted for the purposes of gardening. 5% of ethyl alcohol is enough to stunt plant growth while 25% of ethyl alcohol is enough to outright kill plants.
NOTE: Yeast is the same organism used in the brewery, distilling, and baking business. Yeast helps us produce our favorite alcoholic beverages and pastries.
2 – Do Not Use Boiling Water
The starchy water must be cool or lukewarm before it can be used. Applying boiling water will deteriorate the plant’s cell walls and kill beneficial microbes in the soil.
Boiling water serves as a good, natural weed killer but is horrible for any plant you actually want to keep alive. Make sure that the boiling water is sufficiently cooled to at least 40.5°C (104.9°F) before use.
3 – Do Not Use Starchy Water After Applying Fertilizer
Applying starchy water on plants already fertilized results in nutrient burn in plants. Excess nutrients overload the natural metabolic and photosynthetic process in plants resulting in adverse effects such as stunted growth, curled and yellowed leaves, and root rot.
Starchy water already acts as a mild fertilizer so applying it increases the chances of nutrient burn. It is better to experiment with starchy water when the fertilizer has already been used up by the plants which takes around 2-9 months.
4 – Do Not Use Salt
Using salt during the boiling process prevents the starchy water from being used as a mild fertilizer. Saltwater dehydrates plants, stunts growth, and prevents the consumption of essential plant nutrients.
Like boiling water, salted water can be used as a natural weed killer but is horrible for any plants you actually want to grow. Fortunately, salt used in boiling pasta or potatoes is quite minimal, the effects of any erroneous watering will subside between 3-4 weeks.
NOTE: This is why the term “salting the earth” or “sowing the salt” makes sense. Salt prevents plant life from growing. The salt will naturally dissolve and be washed away by the rainwater but it may take years if a great amount of salt was used.
5 – Do Not Ferment for More Than 12 Days
Studies using fermented starchy water did not ferment it for more than 12 days. The fermentation periods were 3, 6, 9, and 12 days.
Though there is no source detailing the effects of prolonged fermentation on soil health and plant growth, it is better to be safe than sorry. Even if it is noted that longer fermentation may produce a more potent fertilizer, it is safer to stick with the maximum 12 days fermentation period and follow the guidelines set by researchers until new studies have been released.
Drawbacks of Using Starchy Water
The major drawback of using starchy water, fermented or not, from either pasta, rice, noodles, or potatoes is that they attract insects. This is because insects are naturally starch for breeding purposes.
This is why you can find weevils in rice, flour mites in flour, and potato bugs in potatoes. This is why our pantries are often invaded by insects. Fortunately, these insects do not directly harm the plants but can be unnerving for some gardeners.
To prevent insects from gathering, insect-repelling plants like Thyme, Oregano, or Basil, can be grown near the affected soil. Furthermore, the use of either commercial or natural insecticides can repel insects more efficiently due to their purpose-built design.
Rice Liquor (Sake)
Sake is a cherished beverage in Japan made from fermenting rice with its bran polished off. Alcoholic at around 14-16%, uncarbonated, and slightly sweet, sake is a unique beverage that is neither wine, beer, nor spirit.
The process involves cooking the rice, adding crushed yeast balls, then straining the wet mix in a sealed container for 1 month. The process is fairly simple but becomes more complex if you want the alcohol to settle.
For the alcohol-inclined and rice-loving gardener, this is a match made in heaven. Rice water in your home can either be used to feed your desire for alcohol or your plant as an alternate water source and mild fertilizer.
Summary of Using Leftover Pasta Water
Leftover pasta water can be used as a watering source and/or mild fertilizer. It is rich in starch and nutrients derived from the boiling and cooking process of pasta.
Leftover pasta water, upon cooling to a temperature below (40.5°C or 104.9°F), can be used 1) direct-to-soil or 2) fermented. Using the pasta water direct-to-soil can induce beneficial microbe growth in the soil whereas fermented pasta water serves as a mild fertilizer that has more nutrients.
The same principles also apply to other starch-rich foods that are usually mixed with water for cleaning or for boiling. These starch-rich foods include rice, dried noodles, and potatoes.
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