Crop guide · Capsicum annuum

Capsicum (sweet pepper): what to measure and why

Capsicum pays for consistency and punishes swings. The losses that cost most in a pepper house — blossom end rot, flowers dropping in the afternoon heat and growth quietly stalling in a sealed house — are control problems, not input problems.

Also known as Pilipili hoho

Growing conditions

The ranges capsicum (sweet pepper) cares about

General agronomic ranges. A soil test and your agronomist decide the final numbers for your variety and site.

FactorRangeNote
Day air temperature21–27 °CFruit sets reliably in this band
Night air temperatureabove ~15 °CCold nights slow growth and set
Flower abortionabove ~32 °CPollen viability collapses; flowers already made are shed
Relative humiditybelow ~85 % overnightHeld above this, botrytis and powdery mildew build
CO₂ in daylightnear ambient (~420 ppm)Below ~300 ppm CO₂ becomes the growth limiter
Root-zone salinitybelow ~2.0 dS/mModerately salt-sensitive; quality suffers above this
Soil pH6.0–6.8Typical target range; confirm with a soil test

Risks

Where capsicum (sweet pepper) loses yield

Blossom end rot

The sunken black patch at the base of the fruit is calcium failing to reach the fruit tip. Calcium travels with water, so irregular watering — dry spells then heavy soaks — causes it far more often than calcium-poor soil. Steady moisture fixes it; calcium sprays usually do not.

Root rot

Pepper roots are shallow and dislike both drying out and standing wet. Sustained saturation invites Phytophthora, effectively untreatable once established. Water little and often — several short pulses a day.

Heat flower drop

An unvented house in midday sun passes 40 °C easily. Extraction staged on temperature keeps the house out of the band where flowers abort.

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