Growth, Flowering, and Fruit Production of Strawberry ‘Albion’ in Response to Photoperiod and Photosynthetic Photon Flux Density of Sole-Source Lighting

Beyond producing leafy greens, there is a growing interest in strawberry production on indoor vertical farms. Considering that sole-source lighting is one of the most important components for successful indoor crop production, we investigated how photosynthetic photon flux density (PPFD) and the photoperiod of sole-source lighting affected plant growth, flowering, and fruit production in strawberry ‘Albion.’ Bare-rooted strawberry plants were grown in deep water culture hydroponics inside an indoor vertical farm at 21 °C under white + blue + red light-emitting diodes at a PPFD of 200, 300, or 450 µmol∙m⁻²∙s⁻¹ with a 12-h or 16-h photoperiod. Under both photoperiods, increasing PPFD from 200 to 450 µmol∙m⁻²∙s⁻¹ linearly increased crown diameter by 18–64%, shoot fresh and dry mass by 38–80%, and root fresh and dry mass by 19–48%. Under a PPFD ≥ 300 µmol∙m⁻²∙s⁻¹, root fresh and dry biomass increased by 95–108% and 41–44%, respectively, with an increasing photoperiod from 12 to 16 h. In addition, increasing the photoperiod from 12 to 16 h accelerated flowering by 17–21 days under a PPFD ≥ 300 µmol∙m⁻²∙s⁻¹ and first fruit harvest by 17 days at a PPFD of 450 µmol∙m⁻²∙s⁻¹. Regardless of PPFD, strawberry fruit production (g·m⁻²·month⁻¹) increased by 372–989% under a 16-h photoperiod in comparison to under a 12-h photoperiod. In contrast, there was little effect of PPFD on fruit production. Our results suggest that increasing the PPFD or photoperiod can increase strawberry plant growth, but increasing the photoperiod can have a dominant effect on increasing early fruit production in strawberry ‘Albion’.