Stains / spots & Deformation / malformed growth & Discoloration

Calcium Deficiency (Ca)

📍

Affected area New leaves / Shoot tips, Leaf tips

📈

Wachstums-Check Deformed / crippled new growth, Very slow growth, Gradually gotten worse

Erkennungsmerkmale

⚠️ Verwechslungsgefahr

Since calcium is an immobile nutrient, deficiencies first appear at the youngest shoot tips at the top. Characteristically, small, rusty-brown or yellowish spots appear, which enlarge and cause the leaf tissue to become necrotic. Unlike spider mites (white spots), these spots are more irregularly distributed and brownish in color when there is a calcium deficiency.

Go to solution

Ursachenforschung: Was ist passiert?

Water that is too soft (RO water without remineralization), incorrect pH (below 6.0 in soil), or excessively high humidity, which inhibits the transpiration stream (water transport from root to leaf).

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

Calcium is essential for the stability of your cannabis plants' cell walls. To address this, you should take a two-pronged approach: climate and chemistry.

Since calcium is only transported through the leaves via transpiration, the humidity in the grow tent must be stable between 45% and 55%. If it's too high, the calcium gets stuck in the plant and doesn't reach the tips.

In the second step, adjust the pH of the irrigation water to 6.5 (soil) to ensure maximum absorption.

Use a high-quality CalMag supplement. For LED grows under powerful full-spectrum lamps, the calcium requirement is often twice as high as under HPS.

If you use RO water, adding calcium supplements is mandatory with every watering. A severe deficiency leads to brittle stems and makes the plant more susceptible to fungal infections like Botrytis (bud rot).

Once damaged tissue (rust spots) does not regenerate, therefore monitoring new growth at the tips is the only indicator of successful treatment.

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?

Empfohlenes Hilfsmittel

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Mineral Charge

€12,90

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Expert tools for the next step

After diagnosis, the right decision counts

Not every symptom requires the same next step. If you're specifically looking for the right Living Soil input, our Nährstoff-Finder can help. If you want to strategically align your setup to pot size, experience, goal and nutrients, our Living Soil Navigator will guide you further.

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