Evaluating baby-leaf salad greens for spring and fall production in northwest Washington

Charlene Margaret Grahn

Salad crops such as lettuce (Lactuca sativa L.), spinach (Spinacea oleracea L.), kale (Brassica oleracea L.), arugula (Eruca sativa L.), and mustard greens (Brassica juncea L.) thrive in the cool climate of northwest Washington. Baby-leaf salad mix is a staple commodity in the region’s agricultural production system, which relies heavily on high-value specialty crops and direct marketing channels. Growers in northwest Washington currently produce baby-leaf salad crops from June through September; however demand for this crop is year-round. Factors that limit extended-season production of baby-leaf salad crops include low soil temperatures, excessive rainfall, shifting day lengths, and weed pressure. This project addressed these production challenges in five ways. First, semi-structured interviews were conducted with key informants actively participating in the babyleaf salad greens supply chain of Whatcom and Skagit Counties to understand the challenges and opportunities present for growers, purchaser, and consumers in the region. Second, 10 salad crop cultivars were evaluated in spring and fall production trials for two years at two locations in northwest Washington. Significant differences in yield, days to harvest (DTH), and weed biomass were observed between seasons, locations, years, planting dates, and cultivars (P = 0.0001 for all). Third, a set of USDA lettuce germplasm accessions (103 single-parent lineage, homozygous romaine and leaf types) was assayed for percent germination at 5 °C to test for variation among lettuce lines in ability to germinate rapidly under cold conditions. Significant differences in percent germination at 5 °C were observed after 7 and 10 days (P = 0.0001 for both). Fourth, bed flaming was tested for efficacy as a weed management technique for organic production of baby-leaf arugula. Two weeks after seeding, flaming reduced the number of weeds in a bed of baby-leaf arugula by 44% (P = 0.0001), and flaming immediately before or after seeding had no impact on arugula stand (P = 0.99). Lastly, yield of Salanova lettuce cultivars (head lettuce cultivars grown for baby-leaf salad mix) were compared to traditional baby-leaf lettuce production. Salanova heads produced 1.6 to 4.7 greater yield than traditional baby-leaf lettuce (P = 0.004).

Evaluating baby-leaf salad greens for spring and fall production in northwest Washington

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