How to Identify When Dormancy Has Finished

Dormancy release is a biological transition, not a calendar event. Knowing when it has occurred is critical for correctly using GDD / GDH models.

This page explains practical indicators of dormancy release across common crops.

Why this matters

GDH and GDD are only meaningful after dormancy has ended.

If you start accumulating thermal time too early: - Predictions will be wrong - Development will appear delayed - Management decisions may mistime risk windows

Dormancy release: what actually changes

When endodormancy ends: - Buds regain responsiveness to warmth - Growth resumes once temperatures allow - Hormonal suppression is lifted

The plant becomes temperature-limited, not dormancy-limited.

Primary indicators of dormancy release

1️⃣ Bud responsiveness test (conceptual)

If buds: - remain inactive under warm conditions → dormancy persists - begin swelling or greening → dormancy has ended

This principle underpins all dormancy models.

2️⃣ Visual cues (most practical)

Woody perennials (apple, cherry, vine)

• Buds swell uniformly
• Bud scales loosen
• Green tissue becomes visible
• Response occurs across the plant, not just isolated buds

Strawberry (including everbearers)

• New leaf emergence accelerates
• Crown produces consistent new growth
• Flower trusses emerge evenly

Patchy response suggests incomplete dormancy release.

3️⃣ Growth synchrony (very important)

Dormancy release is indicated by: - Uniform response across plants - Uniform response across buds

Uneven growth = partial dormancy or insufficient chill.

Secondary indicators

Thermal responsiveness

• Growth rate increases sharply with temperature
• Warm spells now produce visible response

Reduced chilling sensitivity

• Further chill exposure does not change behaviour
• Warmth, not cold, becomes the limiting factor

What dormancy release is NOT

• A specific date
• A fixed chill unit number
• A sudden overnight event

It is a transition zone, not a switch.

Common mistakes

• Starting GDD accumulation too early
• Assuming calendar dates equal dormancy release
• Ignoring uneven bud behaviour
• Confusing ecodormancy with endodormancy

Practical guidance for Agrinomy users

• Use chill models to estimate readiness
• Use crop observation to confirm release
• Start GDH tracking once responsiveness is observed
• Expect a short overlap period where interpretation is fuzzy

Key principle

Chill unlocks growth — observation confirms it.