Day-neutral strawberry (Fragaria ×ananassa) cultivars show promise for extending the fruiting season and increasing production in the northeastern United States, but published research on cultivar yield in the region is lacking. Furthermore, few studies have investigated the effects of low tunnels on yield, fruit, and plant characteristics. We evaluated eight day-neutral cultivars (Albion, Aromas, Cabrillo, Monterey, Portola, San Andreas, Seascape, and Sweet Ann) on open beds and under low tunnels in two separate experiments conducted in 2017 and 2018. Cultivars began producing ripe fruit within 10 weeks of planting in both years, and continued producing fruit without interruption for 20 weeks (2017) and 18 weeks (2018). Annual total yield ranged from 234.9 to 497.8 g/plant and marketable yield ranged 126.4 to 389.1 g/plant, depending on cultivar and year. Cultivar significantly affected the percent marketable yield, late season yield, fruit size, soluble solids content (SSC), runner emergence, and plant size. Except for the cultivar Sweet Ann, low tunnels did not increase season-long marketable or total yield, but did increase the percent marketable yield for all cultivars in 2017, and most cultivars in 2018. Furthermore, marketable yield was significantly greater under low tunnels than open beds during 6 late-season weeks in 2018. Fruit SSC was greater under low tunnels in 2018, and low tunnels reduced runner emergence for certain cultivars. Season-long average air temperatures were higher under low tunnels, but the greatest temperature differences occurred when low tunnels were closed. We demonstrate that day-neutral cultivars can produce high annual yields in New England, but that cultivar selection is paramount.

Day-neutral (DN) strawberry (Fragaria ×ananassa) cultivars have potential to produce high yields in New England and greatly extend the period of regional strawberry production each year. However, DN strawberries have primarily been evaluated as an annual crop in cold climates; thus, winter hardiness and subsequent second-year spring yields are not well understood. Separate DN plantings were established as dormant bare-rooted plants in Durham, NH (U.S. Department of Agriculture hardiness zone 5b) in 2017 and 2018. During their first year of growth and fruit production, plants were grown under one of two cover treatments: a plastic-covered low tunnel or the traditional open field environment (open beds). In November, plants were covered with either straw much (Winter 2017–18) or rowcover (Winter 2018–19) for low-temperature protection during the winter months. In the spring of the second year when winter protection was removed, the same cover treatments (low tunnel or open bed) were re-administered to plants. Plant survival was affected by year and cultivar, with average survival rates of 82% and 98% in Spring 2018 and Spring 2019, respectively. Plant survival ranged from 34% (‘Monterey’) to 99% (‘Aromas’) in 2018, and 92% (‘Albion’) to 100% (‘San Andreas’ and ‘Seascape’) in 2019. Cultivar significantly affected total and marketable yields in both years, and marketable yields ranged from 35.8 to 167.3 g/plant in 2018 and 121.6 to 298.6 g/plant in 2019. The greatest marketable yields were produced by ‘Aromas’, ‘Cabrillo’, ‘San Andreas’, ‘Seascape’, and low-tunnel ‘Sweet Ann’. In 2019, ‘Cabrillo’, ‘San Andreas’, and ‘Seascape’ produced greater marketable yields during the 6-week second-year season than they had during the plants’ first year of fruit production the previous year, which spanned 18 weeks. Low tunnels hastened fruit ripening in the spring and result in earlier fruit harvests, and in 2019, marketable yields were significantly greater under low tunnels for the first 1 to 3 weeks, depending on cultivar. Total and marketable yields were unaffected by low tunnels in 2018, but were significantly greater under low tunnels in 2019. For cultivars in the 2019 experiment, the increase in marketable yield under low tunnels (compared with open beds) ranged from 92.3 to 166.5 g/plant, except for Sweet Ann, for which marketable yields were 256.6 g/plant greater under low tunnels than on open beds. Using a conservative direct market rate of $4.50/lb, the second-year spring yields produced in the present study had a direct market value of between $3899/ha and $95,647/ha, depending on cultivar and year. We demonstrate that it is not only possible to overwinter DN strawberry plants in northern New England, but that the second-year yield may even exceed first-year production. The results from the present study indicate great potential for profitability from an overwintered DN crop.

Fall planting of spinach (Spinacia oleracea L.) into high tunnels for harvest from late fall through early spring is widely practiced in the northeastern United States, but replicated studies focusing on this production system are lacking. The objectives of our study were to understand the effect of fall planting date (PD) and cultivar on yield and soluble solids content (SSC) of spinach. Three cultivars (Regiment, Space, and Tyee) were transplanted in unheated high tunnels in Durham, NH, in 2014–15 (Year 1) and 2015–16 (Year 2) at six different fall dates: 20 Sept., 30 Sept., 9 Oct., 19 Oct., 30 Oct., and 9 Nov. Five additional cultivars (Carmel, Corvair, Gazelle, Emperor, and Renegade) were included at the third date (9 Oct.) to compare yield and SSC among cultivars during winter months. A randomized complete block design with four replications was used for all experiments. Year and fall transplant date had a significant effect on total yield. Total yield of Year 2 was nearly double that of Year 1 for all PDs and cultivars. In both years, total yield decreased with later planting, such that yield from the 20 Sept. date was greater than a minimum of three of five subsequent PDs, depending on year. Total yield in spring (January through April) did not differ among the first four PDs in Year 1 or among any dates in Year 2, suggesting that a wide range of PDs will work well for those primarily interested in spring harvests. Combined analyses of the data from both years showed no significant differences in total yield among the eight cultivars planted only on 9 Oct. However, of the three cultivars grown at all PDs, Regiment produced significantly higher yields than Tyee. Harvest date, cultivar, and harvest date × cultivar affected leaf and petiole sap SSC in both years. SSC was most strongly negatively correlated with air and soil temperatures at a 10-day interval in Year 1 (R2 = 0.61 and 0.64, respectively) and a 7-day interval in Year 2 (R2 = 0.78 and 0.69, respectively). ‘Gazelle’ and ‘Emperor’ contained among the highest SSC in both years. Our work demonstrates total yield is highly dependent on fall PD and the growing conditions of a given year.

The impact of photoselective films on strawberry plants in a low tunnel system has not been well investigated in the northeastern United States, nor have there been studies looking at the effect of mulch color in a plasticulture system. During two separate years (2016 and 2017), we evaluated ‘Albion’ in an annual system with three ground mulch treatments (black plastic, white-on-black plastic, and no plastic) and under six cover treatments. Five of the cover treatments were low tunnel films that varied in their ultraviolet, photosynthetically active, and near-infrared radiation transmission profiles: Tufflite IVTM (TIV), KoolLite Plus (KLP), Trioplast (TRP), and custom-manufactured UV-transparent (UVT) and UV-blocking (UVO) films. The sixth cover treatment was the traditional open bed environment (no low tunnel). ‘Albion’ produced fruit for 18 to 19 continuous weeks during both years until as late as Thanksgiving (24 Nov.) in 2016. Overall, the average marketable yield was greater in 2017 (486 g/plant) than in 2016 (350 g/plant), and it was greater on black mulch than on no mulch (445 vs. 380 g/plant, respectively); white mulch was intermediate (419 g/plant) (P ≤ 0.05). There was not a significant increase in marketable yield under low tunnels compared with open beds. The average fruit mass was greater under KLP and UVO than open beds (TIV and UVT were intermediate), and greater on beds with no mulch than black mulch (white mulch was intermediate). Across cover treatments, plants on black mulch produced more runners than plants on white or no mulch, and the black mulch/open bed treatment generated the greatest number of runners in both years, more than double most other treatments in 2016. The present study demonstrates that mulch selection is important for maximizing the yield of ‘Albion’ in the Northeast region, and that both mulch and cover impact runnering and fruit size. For plant propagators producing ‘Albion’ tips in a field environment, the results of this study suggest they are likely to maximize runner quantity by cultivating plants on black mulch without low tunnel cover.