Blossom end rot is a black, sunken, soft patch at the flower end of tomatoes, peppers or courgettes — NOT a fungal disease! It is a calcium uptake disorder.
Causes
NOT soil calcium deficiency — the plant cannot transport it fast enough. Causes: uneven watering, excess nitrogen, low pH, root damage.
Organic prevention
- 💧 Drip irrigation — most important measure!
- 🌾 Mulching (10-15 cm straw)
- 🪨 Lime if pH is below 6
- 🌿 Calcium foliar spray (calcium nitrate 1-2 g/l)
- ❌ Avoid excess nitrogen during flowering
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Summary
Blossom end rot is NOT infectious — calcium uptake problem. Drip irrigation + mulching + correct feeding. Remove affected fruits — the plant stays healthy!
- What is blossom end rot and is it a fungal disease?
Blossom end rot is a black, sunken, soft patch at the flower end of tomatoes, peppers or courgettes. Importantly: this is NOT a fungal disease or infection. It is a calcium uptake disorder — the plant cannot transport enough calcium into the fruit quickly enough, causing tissue breakdown.
- What causes blossom end rot if the soil has calcium?
It is not soil calcium deficiency — most soils contain plenty of calcium. The plant struggles to transport it into the fruit. Main causes: uneven watering (drought followed by heavy watering), excess nitrogen during flowering, low soil pH (below 6), or root damage. Only the growing fruit tissues starve of calcium.
- How can you prevent blossom end rot organically?
Drip irrigation is the most important — consistent moisture ensures steady calcium uptake. Mulch with 10–15 cm straw to maintain even soil moisture. If pH is below 6, apply lime (dolomite limestone). Avoid excess nitrogen during flowering. Remove affected fruits early — the plant remains healthy and continues producing.
- Can calcium foliar spray help with blossom end rot?
Yes, calcium nitrate solution (1–2 g/l) sprayed on leaves can help — calcium is absorbed directly. However, this is a short-term fix. Long-term success requires consistent drip irrigation, mulching, correct soil pH, and balanced nitrogen feeding. Once symptoms appear, the fruit cannot be saved, but new fruits will form healthy.