Thermal Dormancy in Strawberries: How Fogging Can Protect Your Crop Flow
Thermal dormancy is emerging as one of the most pressing agronomic challenges facing UK strawberry producers. With periods of sustained high temperatures becoming more common, the impact on flowering, fruit set and overall crop consistency is increasingly difficult to ignore — and often harder to detect until damage has already been done.
"When temperatures climb too high, the plant effectively shifts into a protective state — prioritising its own survival over reproduction."
Outwardly, the crop can appear perfectly healthy and continue to grow vegetatively. But beneath the surface, reproductive activity has stalled. The danger is that this often goes unnoticed until it manifests as a gap in flower development, a drop in fruit set, or an unexpected fall in picking volumes.
Understanding Thermal Dormancy
In strawberry crops, thermal dormancy is triggered when temperatures exceed the threshold at which the plant can comfortably support both vegetative growth and flower development simultaneously. Faced with heat stress, the plant makes a physiological trade-off — diverting energy away from flowering and towards basic survival functions.
The downstream effects are well documented: reduced flower quality, disrupted development, compromised pollen viability and, ultimately, weaker fruit set. Growers often see this expressed as increased numbers of misshapen berries, smaller fruit size and inconsistent ripening across the crop.
"Once the signs of thermal dormancy become visible in the crop, a portion of the future harvest has likely already been compromised. Intervention needs to happen earlier — at the point heat stress begins, not after it has taken hold."
The Risk to Crop Programming
For growers operating within tightly managed retail supply programmes, the consequences of thermal dormancy reach well beyond simple yield loss. The real risk lies in the disruption to crop flow and the predictability that commercial programmes depend on:
- Reduced weekly picking volumes
- Lower proportion of Class 1 fruit at packout
- Uneven ripening creating inefficiencies in harvest and packhouse operations
- Increased labour cost per kilo picked
- Reduced confidence in volume forecasts and retailer commitments
"Commercial strawberry production is fundamentally about delivering the right volume at the right time. When heat stress disrupts the flowering cycle, the entire crop curve shifts — creating knock-on problems for labour scheduling, packhouse throughput and retailer relationships."
In a precision-managed crop, losing control of that predictability can ultimately be more costly than the direct yield loss itself.
The Case for Proactive Cooling
The most effective approach to managing thermal dormancy is not reactive — it is preventative. Waiting for visible signs of stress before acting means the physiological damage has already occurred. The focus should be on maintaining favourable growing conditions during high-risk periods, before the crop begins to struggle.
Fogging systems offer a practical and targeted way to achieve this. By generating an ultra-fine water mist within the growing environment, they create an evaporative cooling effect that can meaningfully reduce both air temperature and canopy temperature — helping to keep the crop within its productive range during hot spells.
IrriSmart Fogging Solutions for Soft Fruit
Our Super Fogger and 4 Way Fogger have been widely used in polytunnel and glasshouse environments for exactly this purpose. Both units produce a fine droplet mist that delivers effective evaporative cooling without saturating the crop or creating conditions that could interfere with pollination.
Super Fogger — suited to larger tunnel bays and high-output applications, providing consistent fine droplet distribution across a wide canopy area.
4 Way Fogger — a flexible multi-directional unit well suited to zone-specific cooling or smaller growing structures. Both systems are straightforward to integrate with existing irrigation pipework and can be operated on a timed or temperature-triggered basis, allowing growers to respond automatically when conditions reach critical thresholds.
Summary
Thermal dormancy represents both an agronomic and a commercial risk for strawberry producers. Proactive management of canopy temperature during hot periods — rather than reactive intervention after stress has set in — is one of the most effective tools available to protect flower initiation, maintain fruit set and preserve the crop flow that retail programmes depend on.
To discuss fogging system design for your soft fruit operation, contact the IrriSmart team.