Adding a small amount of citrus juice to irrigation water introduces citric acid to the soil. This technique is intended to subtly lower the soil’s potential of hydrogen (pH) level. The goal of this acidification is to improve growing conditions for specific plants that naturally prefer a lower pH environment, especially when dealing with neutral or alkaline soil conditions.
Why Soil Acidity Matters for Plant Health
Soil pH is a fundamental factor that governs a plant’s ability to absorb nutrients. A slightly acidic to neutral pH, ranging between 6.0 and 7.5, is optimal because most essential macro- and micronutrients are readily available to plant roots within this range. When the soil becomes too alkaline, meaning the pH rises above 7.0, the chemical properties of the soil change dramatically.
In alkaline conditions, necessary micronutrients like iron, manganese, and zinc can become chemically “locked up.” These elements precipitate, forming insoluble compounds that cannot be dissolved in water. Even if these nutrients are physically present in the soil, the plant cannot absorb them through its roots, leading to a state of functional deficiency. This highlights why acid-loving plants often show signs of nutrient distress when grown in high-pH soil.
This micronutrient deficiency frequently manifests as interveinal chlorosis—a yellowing of the leaves while the veins remain green. This is a common sign of iron deficiency in plants struggling in alkaline soil. Altering the soil pH, even slightly, can shift these insoluble compounds back into a soluble form, making them accessible once again for plant uptake.
Plants That Thrive with Acidic Water
The plants most likely to benefit from an occasional application of lemon water are obligate acid-lovers, which naturally require a soil pH well below 6.0. These specialized plants thrive in environments where a lower pH keeps their preferred micronutrients in a soluble, absorbable state. Examples include Azaleas and Rhododendrons, which perform best in a pH range of 4.5 to 6.0.
Camellias and Gardenias are particularly susceptible to iron and manganese deficiencies in neutral or alkaline soils. When these plants exhibit yellowing leaves, it is often an indication that the soil pH is too high, preventing them from accessing iron. The addition of a mild acid can temporarily free up these bound nutrients, providing a noticeable greening effect.
Blueberries require an acidic environment, ideally between a pH of 4.5 and 5.5. If grown in higher pH soil, their growth becomes stunted, and they fail to produce a healthy crop. The targeted use of a diluted acid can help mitigate these symptoms for a short period, especially in container gardening where the soil volume is smaller and easier to manage.
Safe Application and Risks of Using Lemon Water
Using lemon juice to acidify soil is a temporary measure that requires caution due to the high acidity of concentrated citrus juice. Undiluted lemon juice contains citric acid strong enough to burn a plant’s roots and kill beneficial soil microorganisms. It should only be used for plants showing symptoms of alkaline soil stress, like chlorosis.
A safe starting dilution is one to two tablespoons of lemon juice mixed into a gallon of water. This ratio ensures the acid is dispersed sufficiently to provide a mild pH-lowering effect. This acidified water should only be applied occasionally, not with every watering, as continuous application can lead to over-acidification of the soil, which can harm the plant.
Most common garden plants and vegetables prefer a near-neutral pH and will be harmed by significant acidification. Using lemon water on plants that are not acid-lovers will lead to nutrient imbalances and potential toxicity from elements like aluminum becoming too soluble. Gardeners should always test their soil pH before attempting any acidification.