Encyclopaedia

thermal → frost_risk_by_stage

Spring Frost Risk by Phenological Stage

Spring frost damage risk depends far more on crop development stage than on the absolute temperature alone.

This page explains how frost sensitivity increases as phenology advances.

Why phenology matters more than date

Dormant buds tolerate very low temperatures
Actively growing tissues are highly sensitive
Risk increases rapidly after dormancy release

Frost risk should be assessed relative to phenological stage, not calendar date.

General frost sensitivity by stage (temperate crops)

Stage	Typical BBCH	Relative frost sensitivity
Dormant bud	00–01	Very low
Bud swell	01–03	Low
Green tip	07–09	Moderate
Tight cluster	51–53	High
First bloom	60–61	Very high
Full bloom	65	Extreme
Petal fall / fruit set	69–71	Very high

How chill and GDH affect frost risk timing

High chill + slow GDH → later budbreak, reduced frost exposure
Low chill + early warmth → early budbreak, extended frost risk window

Warm winters often increase frost risk, not reduce it.

Practical implications for growers

Monitor phenological stage, not just minimum temperatures
Frost protection decisions should be stage-based
The most dangerous period is often just after budbreak, not mid-winter

Agrinomy usage

Agrinomy links: - Chill fulfilment → dormancy release - GDH accumulation → stage progression

This allows frost risk to be assessed in context, not in isolation.

Key principle

Frost damage is a timing problem, not just a temperature problem.