Outdoor & Protected Cultivation
Frost, Heat & Seasonal Extremes
Outdoor crops experience radiative cooling, frost pockets, heat waves, hot surfaces, and abrupt weather transitions. Risk depends on plant stage, local topography, soil and ground cover, wind, humidity, and duration of exposure.
Key concepts
- Low areas can accumulate colder air on calm nights
- Soil moisture, texture, and ground cover change heat storage and nighttime release
- Heat stress depends on radiation, leaf temperature, water supply, and air movement
- Weather-station readings may not represent the crop microclimate
What to measure or observe
- Record canopy-level minimum and maximum temperature
- Identify low spots and exposed slopes
- Measure or estimate leaf temperature during heat events
- Inspect recovery after an extreme event before making unrelated corrections
Common mistakes
- Using only regional forecast temperature
- Assuming mulch always reduces frost risk
- Increasing irrigation blindly during heat without checking root oxygen
- Diagnosing weather injury as nutrition from appearance alone
Visuals this lesson still needs
- Cold-air pooling diagram
- Soil heat-storage comparison
- Leaf-temperature heat-stress map
- Frost versus heat injury differential