Worked Example: Cold Winter vs Warm Winter
This example illustrates how winter temperature patterns influence spring development,
even when spring temperatures appear similar.
It explains why two seasons with similar spring warmth can behave very differently.
Season A — Cold, Consistent Winter
Winter pattern
- Prolonged periods of cool temperatures
- Few warm interruptions
- Chill accumulates steadily
Dormancy outcome
- Endodormancy fully satisfied
- Buds exit dormancy cleanly and uniformly
Spring response
- Budbreak occurs within a narrow window
- GDH accumulation translates directly into growth
- Flowering is synchronised
- Crop load is predictable
Grower experience
“Everything moved together. Timing felt right.”
Season B — Warm, Fluctuating Winter
Winter pattern
- Frequent mild spells
- Chill accumulation slow and uneven
- Warm periods interrupt chill processes
Dormancy outcome
- Endodormancy only partially satisfied
- Some buds exit dormancy earlier than others
Spring response
- Budbreak stretched over time
- GDH accumulates, but growth lags
- Flowering extended and uneven
- Increased management complexity
Grower experience
“It felt like the crop never really got going properly.”
Why spring warmth doesn’t fix missing chill
GDH (or GDD) can only drive growth after dormancy is fully released.
If chill requirements are not met:
- Warmth accelerates some buds
- Others remain dormant
- Uniform development is lost
Heat cannot substitute for chill.
Practical lessons
- Chill sets the potential for spring growth
- GDH controls the speed of growth after release
- Winter patterns matter more than winter averages
- Warm winters increase risk, even if spring looks good
Key takeaway
Winter history shapes spring behaviour — not the calendar.