Planting Date Affects Yield and Harvest Duration of Organically Managed Salad Mixes in High Tunnels

Salad mixes of baby-leaf lettuce, spinach and mustard greens are high cash-value crops for farmers and an important component of a healthy diet for consumers. A unique characteristic of salad mix production is the allowance for multiple harvests, as leaves of these vegetables can regrow after being cut. High tunnels are an effective tool in achieving season extension in vegetable production; however, information on growing salad mixes in high tunnels is limited. The study was conducted in the spring and fall of 2014 in Greensboro, NC, with an objective to identify ideal direct seeding time for salad green mixes in high tunnels. Lettuce mix ‘Encore’, spinach mix of ‘Tyee’, ‘Emperor’ and ‘Corvair’ and mustard green mix ‘Ovation’ were direct seeded sequentially on three planting dates (D1, D2 and D3) in high tunnels. Planting dates were Feb. 17, Feb. 27 and March 11 in spring, and Sep. 22, Oct. 2, and Oct. 13 in fall, respectively. Seeds were planted in four rows on 76.2 cm wide raised beds. Lettuce and mustard greens were thinned to 1.3 cm apart, and spinach were thinned to 2.5 cm apart. A completely randomized design with three replications was used. Each experimental plot consisted of a 152 cm bed. Harvests were conducted three times a week when leaves reached 8-10 cm high until mid-May or end-December. There were no significant differences among planting dates in total marketable yield of mustard green and spinach mixes for both seasons, while D2 of lettuce mix had a higher yield than D3 in both seasons. In the fall, D1 was harvested 2-7 and 9-21 days earlier than D2 and D3 for all salad mixes; while in the spring, the first harvest of D1 mustard green and spinach mixes occurred later than that of D2. Harvest of mustard green mix was terminated earlier than lettuce and spinach mixes in both seasons, with 5-6 and 9-12 effective harvests (marketable yield > 100g per plot) in spring and fall seasons. On average, the duration from direct seeding to the first harvest was 5-12.7 days shorter in the fall than that in the spring season. This experiment will be repeated in 2015 to draw conclusions on appropriate planting time for production of salad mixes in high tunnel.