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Magnesium Deficiency (Mg)

📍

Affected area Old / lower leaves, Leaf margins

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Wachstums-Check Gradually worsened, Very slow growth, Normal growth

Erkennungsmerkmale

⚠️ Verwechslungsgefahr

Interveinal chlorosis is typical: the tissue between the leaf veins turns yellow or shows brown rust spots, while the leaf veins themselves remain a strong green. It almost always starts on the lower, older leaves, as magnesium is a mobile nutrient that the plant transports upwards.

Go to solution

Ursachenforschung: Was ist passiert?

Often with LED lighting, as the light spectrum increases the demand for magnesium. An incorrect pH value (< 5.8 in soil) or an excess of calcium/potassium (blockage) are also often the cause.

Systemische Einordnung

What is often really behind it

A deficiency is often a problem of availability. A visible deficiency does not automatically mean that this nutrient is absent in the substrate. Often, absorption in the root zone is disrupted by pH fluctuations, excessive moisture, cold, or an unstable soil environment. Especially in the living soil approach, it is therefore not about hastily addressing symptoms with more fertilizer, but about carefully assessing the availability and balance in the soil.

Common associated problems

✓ Grow Lab expert solution

The right treatment

First, check the pH of your medium; for soil, it should be between 6.3 and 6.8 to ensure absorption.

Epsom salt (magnesium sulfate) is a highly effective immediate measure. You can use 0.5g of Epsom salt per liter of water as a foliar spray to directly stop chlorosis in the leaves.

For long-term correction, a CalMag supplement should be added to the irrigation water, especially if you are working with soft tap water or reverse osmosis water.

Ensure a balanced calcium-magnesium ratio of approximately 3:1. The already yellowed areas will not turn green again, but the spread of the deficiency should stop within a few days.

For organic grows, dolomite lime in the substrate helps maintain a stable magnesium balance throughout the entire cycle.

Passende Ratgeber aus dem Magazin

Experten-Wissen

The problem isn't your fertilizer – your tap water is sabotaging your grow.

Experten-Wissen

CalMag 2:1, 3:1 or 4:1 - Which Ratio is Right?

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Mineral Charge

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