22 August 2019, written by Ann Marie Hendry
This summer, my garden faced relentless rainfall, which made it feel like the wet weather would never end. As a result, most of my plants flourished, becoming lush and green—except for my tomato plants. Their healthy green foliage began to develop a concerning yellow hue.
So, what caused this decline in my tomato plants’ health? The answer pointed to one issue: a magnesium deficiency.
Magnesium Deficiency in Tomato Plants
Magnesium is a vital nutrient for tomato plants, as it helps produce chlorophyll, the green pigment that enables plants to photosynthesize. When a tomato plant lacks magnesium, it shows clear symptoms, most notably yellowing leaves with distinct green veins, a condition known as “interveinal chlorosis.” Magnesium deficiency disrupts chlorophyll production, leading to the loss of green color in the leaves.
In some cases, the yellowing progresses to reddish, purple, or brown tints on the leaves, and as the problem worsens, the affected leaves can die off. The lower, older leaves are usually the first to show signs of magnesium deficiency, and if left unaddressed, the plant’s overall health will decline, affecting fruit production.
Causes of Magnesium Deficiency
While magnesium is abundant in most soils, certain factors can lead to a deficiency. Overwatering or overusing fertilizers, particularly those high in potassium (such as specific tomato feeds), can hinder the plant’s ability to absorb magnesium effectively. Magnesium is also easily washed out of sandy or well-draining soils, especially after heavy rainfall.
In my case, the soil around my tomato plants was saturated due to continuous rain, causing moisture to travel through the soil and wash away magnesium. I later realized that I had been watering too frequently.
How to Treat Magnesium Deficiency with Epsom Salts
One of the quickest and most effective ways to correct a magnesium deficiency is by using Epsom salts (magnesium sulfate). Epsom salts are widely available in pharmacies or online and can be easily applied to your plants. Here’s how to use them:
- Prepare the Solution: Dissolve about 1 teaspoon of Epsom salts in 1 liter (or a quarter gallon) of water.
- Apply the Solution: Pour the solution into a spray bottle and mist the leaves of your tomato plants every two weeks. Ensure the solution is evenly applied to the foliage.
- Avoid Overuse: While it may seem tempting to apply more, excessive use of Epsom salts can cause nutrient imbalances. More is not always better. I recommend alternating the Epsom salt treatment with a liquid seaweed feed or a tomato fertilizer containing seaweed, which provides a variety of nutrients and promotes overall plant health.
If the magnesium deficiency is due to excessive potassium fertilizers, avoid using tomato-specific fertilizers until the problem is resolved.
Improving Long-Term Soil Health
While Epsom salts offer a quick fix for magnesium deficiency, improving your soil’s health is essential for preventing future issues. Adding a layer of well-rotted compost as mulch can help. Compost is rich in magnesium and other nutrients, and over time, earthworms and soil organisms will break it down, enriching the soil and improving its ability to retain magnesium and other essential minerals.
By addressing both immediate nutrient deficiencies and long-term soil health, you can restore the vigor of your tomato plants and enjoy a healthier, more productive harvest.