Magnesium Sulfate for Pome Fruit Trees (Apple)

That yellowing between the leaves that isn't a pest (even though it looks like one)

It's one of the most common misunderstandings in the garden: you see yellow leaves and the first thing you think of is a fungus, a pest, or that you've watered incorrectly. But when the yellowing appears mainly on the older leaves, spares the green veins, and is accompanied by premature fruit drop, no pest can be to blame: it's chlorosis due to magnesium deficiency, and it's one of the most common deficiencies in pome fruits such as apple and pear trees, especially in sandy soils or those heavily leached by rain.

🧪 The benefits of magnesium in plants, explained without technical jargon

Magnesium is not a secondary nutrient; it is literally the heart of photosynthesis: it is part of the chlorophyll molecule, and between 15 and 20% of the total magnesium in a tree is concentrated precisely in the chloroplasts, the "factory" where the plant converts light into energy. Without enough magnesium, the plant produces less chlorophyll, photosynthesizes less effectively, and everything else suffers.

In addition to its role in photosynthesis, magnesium:

• Activates numerous enzymes involved in the plant's growth and metabolism.
• Helps transport sugars from the leaves to the fruit, which directly influences its flavor and development.
• Improves fruit coloration, as it promotes the production of carbohydrates, precursors to the pigments responsible for the red color in varieties such as apples.
• Reduces premature fruit drop, a problem closely associated with the deficiency of this nutrient in pome fruits.

🍏 Why pome fruits (apple and pear trees) are so sensitive to magnesium deficiency

Pome fruits have a particularly high demand for magnesium during fruit filling, precisely when they need to transport the most sugars from the leaf to the developing apple or pear. If at that moment the soil does not have available magnesium (very common in sandy or acidic soils, or those with abundant irrigation that leaches out nutrients), the tree prioritizes its own reserves, and the older leaves are the first to show symptoms, because magnesium is a mobile element that the plant redirects toward new growth.

🌿 Why it has to be magnesium sulfate heptahydrate

Not all "magnesium sulfates" are the same. There are anhydrous forms (more concentrated but much less soluble) and the heptahydrate form (MgSO₄·7H₂O), also known as Epsom salt, which is the one recommended for agricultural use due to its extremely high solubility. This is key for two reasons:

• It dissolves better in water, allowing it to be applied both to the soil and as a foliar spray, so that the plant can absorb it quickly.
• It corrects the deficiency faster, which is especially important when you have already seen the symptoms on the leaves and need to act before the next harvest.

Puerto Verde magnesium sulfate heptahydrate provides around 16% magnesium and 32% sulfur, two nutrients that work together: sulfur, in fact, improves the assimilation of other elements and participates in the plant's protein synthesis.

✅ Why it matters that it is 100% natural

In a home garden or a crop intended for personal or family consumption, what you give to the soil eventually, sooner or later, ends up on the plate. A natural magnesium sulfate, without synthetic additives or fillers, guarantees that you are providing exactly the mineral the plant needs, without added residues that could accumulate in the soil with repeated applications throughout the seasons. Furthermore, as it is a mineral of natural origin, it is fully compatible with organic management and sustainable agriculture.

🧂 Why the powdered form is the best option

Magnesium sulfate heptahydrate powder has clear advantages over other pre-prepared liquid formats:

• Precise dosing: you weigh exactly the amount you need for each application, without depending on a fixed factory concentration.
• Better storage: stored in a cool, dry place, the powder remains stable for much longer than a liquid solution.
• More yield per kilo: by buying it concentrated and dissolving it yourself at the time of use, the cost per application is much lower than that of ready-to-use liquid correctors.
• Total versatility: the same powder can be used both for dry soil application and for preparing a foliar solution, depending on what your tree needs at any given time.

📋 How to use magnesium sulfate on your apple tree, step by step

Soil application (basal supply)

1. Spread the magnesium sulfate powder around the tree, in the area under the canopy's projection (where the feeder roots are concentrated), avoiding direct contact with the trunk.
2. Lightly incorporate it into the first few centimeters of soil with a rake if the soil allows it.
3. Water after application to help the product reach the root zone.

Foliar application (faster correction)

1. Dissolve the magnesium sulfate in water at the recommended concentration (see the table below).
2. Apply with a sprayer, thoroughly covering the underside of the leaves, which is where the plant absorbs it best.
3. Choose early morning or late afternoon, avoiding the hottest hours and direct sunlight on the wet leaf.
4. Repeat the application every 15-20 days while symptoms persist, or as preventive maintenance during the active growth phase.

⚖️ Approximate amounts of magnesium sulfate for fruit trees

These amounts are approximate and can be adjusted according to the size of the tree, the type of soil, and the observed degree of deficiency. When in doubt, it is preferable to start with the lowest dose and repeat the application rather than overdosing all at once.

❓ Frequently asked questions about magnesium sulfate in fruit trees