Strawberry cultivars vary in productivity, sugars and phytonutrient content when grown in a greenhouse during the winter

- Strawberry plants flowered and fruited during winter growing conditions, regardless of response time.
- Certain cultivars fruited better during certain months, regardless of response time.
- 'Evie-2', 'Evie−2+' and 'Portola' plants produced the highest berry yield.
- 'Chandler' and 'Seascape' berries contained the lowest concentrations of sugars.
- Overall, 'Seascape' berries contained the highest concentration of phytonutrients.

In many areas of the US, fresh locally grown berries are not available during the winter. With this in mind, a research study comprised of three experiments was conducted focused on cultivar selection for berry yield, number, sweetness and phytonutrient content. Using a capillary mat system with under bench heating within a double-layer polyethylene greenhouse, strawberries were grown in the Great Plains Region of the US during the winter. During experiment 1, 12 cultivars were grown; berries were weighed, counted and analyzed for sugars and phytonutrients. 'Albion' plants produced a high number/mass of berries, had relatively high sugar content but a lower level of phytonutrients when compared to other cultivars. Sugar and phytonutrients concentrations overlapped across cultivars and thus, one cultivar could not be statistically singled out as best. As all cultivars flowered and fruited, two additional 8-month-long experiments were conducted. It took only 7 weeks from potting of dormant crowns for most cultivars to produce fruit. Certain cultivars fruited more successfully during certain months than others, but this was not associated with response time. For example,' 'Albion', 'Chandler', 'Darselect', 'Evie-2′ and 'Seascape' plants consistently produced fruit October to early January while 'AC Wendy', 'Cavendish', 'Honeoye' and 'Strawberry Festival' plants mainly produced berries in March/April. Summed over experiment 2, 'Albion', ' Cavendish', 'Chandler', ' Evie-2', 'Portola' and 'Seascape' plants produced the greatest mass of berries. 'AC Wendy' and 'Darselect' berries contained some of the highest levels of sugars while berries from 'Chandler', 'Darselect', 'Evie-2′, 'Seascape' and 'Strawberry Festival' had some of the highest phytonutrient values. In the third experiment, of the 8 selected cultivars, 'Evie-2′, 'Evie−2+' and 'Portola' plants had the highest total yield and average berry mass/plant. 'Seascape' and' Chandler' plants were second in total production. Glucose, fructose and sucrose levels varied across cultivars with 'Chandler' and 'Seascape' berries possessing the lowest level of total sugars. Phytonutrient values varied among cultivars with some having better flavonoids ('Seascape'), phenols ('Seascape' and 'Chandler') and ant oxidant capacity ('Seascape', 'Evie-2' and 'Cavendish'). Measurement of soluble solids concentration varied by week among the cultivars with 'Seascape', 'Seascape+”, and “Albion” berries possessing higher levels than other cultivars such as 'Cavendish'. Overall, under these winter greenhouse conditions using capillary mat fertigation and an under-bench heat delivery system, strawberries were successfully produced for the off-season market.