How to protect your strawberries from thermal dormancy

“Thermal dormancy is essentially the plant moving into survival mode,” says Mike Stoker, agronomist at Orion FT, who has spent more than two decades working in fruit agronomy.

“The crop may still look green and vegetative, but reproductively it has slowed down. That is where the agronomic risk comes in, because the effect is not always seen immediately. It can show up later as a gap in flowers, reduced fruit set or a dip in picking volume.”

In strawberries, thermal dormancy occurs when high temperatures push the plant away from reproductive growth and towards vegetative survival. Instead of continuing to initiate and support flowers, the plant prioritises maintaining itself.

“The goal for any grower is to reduce the chance of thermal dormancy by helping strengthen the plant to be more resilient to heat stress,” he says. 

He suggests that plant available silicon, including monosilicic acid, is associated with several physiological processes directly relevant to heat stress.

“Tissue strength can be improved by using silicon which is deposited in plant tissues. In addition, the plant’s ability to balance water and deal with heat and moisture stress is improved by using silicon and can also help reduce the risk of dormancy,” he adds.

In practical terms, Stoker believes the value of silicon is strongest when it is used before and during high-risk periods, rather than after symptoms appear.

Flowering and fruit set have suffered in the hot conditions. 

“By the time thermal dormancy is visible, part of the future crop profile may already have been affected,” he says. “The aim should be to build resilience before the plant reaches that point.”

Heat stress can reduce flower quality, disrupt flower development and affect pollen performance. This can lead to weaker fruit set, more misshapen berries and reduced fruit size.

“For growers, the consequences can include reduced weekly volume, lower Class 1 packout, uneven ripening, poorer picking efficiency and higher labour cost per kilo. In a programmed crop, that loss of predictability can be as damaging as the loss of yield itself,” says Mr Stoker.

Neill Finlayson, Operations Director at Angus Soft Fruits, says consistency of production is critical when supplying major retail programmes.

“Strawberry production is all about crop flow. Growers are not just trying to produce yield; they are trying to produce the right volume at the right time. If heat stress interrupts flowering, the crop curve becomes uneven, which creates problems for labour planning, packhouse flow, retailer programmes, forecast accuracy and ultimately profitability.”

As strawberry production becomes more precise, heat stress needs to be managed not only as an agronomic issue, but as a crop programming risk. Thermal dormancy can interrupt flowering, distort supply patterns and reduce confidence in forecast volumes.

“Growers are already very good at reacting to visible stress. The next step is managing the physiology before the crop visibly struggles. That is where silicon fits — as part of a proactive resilience programme designed to help maintain crop flow through difficult conditions,” concludes Mr Stoker.

Orion FT Agronomist, Mike Stoker

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