Flower Retention in Pepper: Liquid Fertiliser Solutions Against Yield Loss

Why do pepper flowers drop?

Using a flower retention fertiliser on pepper is one of the cornerstones of yield security, particularly in greenhouse and protected production. Compared with tomato, pepper is more sensitive to flower drop; even small deviations in temperature, humidity and nutrient balance can cause serious yield loss.

The main causes of flower drop in pepper:

• High night temperature (>20°C): pollen quality deteriorates and fertilisation falls
• Low humidity (<50%): pollen dries out and cannot adhere to the stigma
• Zinc deficiency: pollen tube development stops
• Excess nitrogen: pushes the plant into vegetative growth and suppresses generative development
• Water stress: both too much and too little water increase flower drop
• Thrips (Frankliniella occidentalis): damage flower tissue and cause abscission

Fertiliser combinations that improve flower retention

Zinc (Zn) · the fundamental element for flower retention

Zinc is required for the synthesis of auxin (IAA) from the amino acid tryptophan, and auxin is the hormone that keeps the flower attached to the plant. When zinc is deficient, auxin synthesis stops and leaf and flower drop begin. Zinc given as a foliar fertiliser acts 3–5 times faster than a soil application.

Boron (B) · supports pollen germination

Boron enables pollen to germinate on the stigma and the pollen tube to elongate. Where boron is lacking there are flowers but no fertilisation, so no fruit sets. Because boron uptake falls at low temperatures, it is especially critical for winter pepper growers.

A pepper flower retention programme with Casablanca

Alongside naturally sourced zinc, Casablanca contains trace elements and natural disinfectants. The recommended programme in pepper growing:

• Two weeks after planting: first foliar application (root establishment and early growth)
• When the first flower buds appear: flower retention support begins
• At full flowering: an application every 10 days
• After the first harvest: repeat for the second and third flowering waves

Points to watch under greenhouse conditions

In greenhouse pepper production, climate control matters as much as fertiliser:

• Night temperature should be held between 15 and 18°C. Above 20°C flower drop increases.
• Humidity should be 60–70%. Pollen dries at low humidity; fungal disease increases at high humidity.
• Ventilation is critical: CO₂ enrichment and air circulation improve photosynthesis and fertilisation.
• Pollination by hand or vibrating pollinator: gently shaking open flowers achieves mechanical pollination.

Flower retention in open-field pepper

In open-field pepper production bee activity is important. Keeping nectar plants nearby and moving insecticide applications outside the flowering period supports the bee population.

In the open, Casablanca should be applied early in the morning (before bees are active) or towards evening. That way pollinators are not harmed and the fertiliser works at full efficiency.

Frequently asked questions

When is a flower retention fertiliser used on pepper?

It should start a week before the first flower buds appear and continue at 10-day intervals until the end of the harvest period.

Why do pepper flowers drop?

The most common causes are high night temperature, zinc and boron deficiency, low humidity, excess nitrogen fertilisation and thrips damage.

How is Casablanca used on pepper?

Apply 150–200 ml of Casablanca per 100 litres of water as a foliar spray. It can also be delivered through the drip system. Early morning or evening application is recommended.

Does low humidity cause flower drop in greenhouse pepper?

Yes · when humidity falls below 50% the pollen dries and fertilisation cannot take place. A fogging system or regular ventilation is needed for humidity control in the greenhouse.