LED lighting has the potential to make year-round production of indoor grown strawberries a commercial reality for UK growers.

That was the interim conclusion of a study by the University of Reading’s Soft Fruit Technology Group in partnership with, among others, NIAB/EMR in Kent, which was presented at the National Fruit Show in October.

PhD student Kieri Swann, said that while more work was needed to establish the optimum light spectrum and intensity ranges, the study had demonstrated that winter yields in excess of 100t/h could be achieved without the use of CO2 in vertical growing systems, based on the Ever-bearer variety and harvesting in February.

“The main reason for using supplementary lighting is to extend the season,” said Swann. “Traditionally, high-pressure sodium lights have been used, but they are fairly inefficient. LED light spectrums, on the other hand, are tunable and you can achieve more intensive light levels [without scorching the plants] because they are cooler.”

The study monitored yield, photosynthetic rate, fruit quality, plant morphology, and system efficiency. It showed that photosynthesis and yields increased dramatically as light levels were ramped up to around 350µmol – between 227µmol and 344µmol yields jumped by 13%.

While the blue:red light ratio was shown to have no critical impact on the plants’ performance, more far-red light and increased green light could both boost yield – and the latter produced better working conditions for staff.

Higher temperatures produced earlier crops but they also had the effect of suppressing yields.

Meanwhile, UK-owned Global Berry is set to become the first grower in the UK to produce a commercial winter crop of strawberries this December.

Its sister company GD Lights recently completed a successful £3million fund raise to install LEDs at Global Berry’s Somerset site. It’s predicting a 58% uplift in yield and a 25% premium for winter-grown fruit.