How can Midwestern growers make the most of winter high tunnel real estate for winter salad mixes?

View the project final report

Commodities

• Vegetables: greens (leafy), greens (lettuces)

Practices

• Crop Production: continuous cropping, greenhouses, high tunnels or hoop houses

Optimizing production in winter high tunnels relies on careful selection of crops, because winter plant growth is so slow and limited. Every year, we consider winter market demand and plant crops that we know will grow well, but carried out this project because we sought better data on the relative yields of our various potential salad mix ingredients so that we could make the most informed decisions about what to plant and how to use our precious tunnel space for the best winter yields. 

Winter vegetable production provides growers with great opportunities to enter untapped markets, to distinguish themselves with niche products, and to spread their income through the year. At the winter Worthington Farmers Market, the largest farmers market in Columbus, we regularly sell out of our produce early in the market, suggesting that the market could accommodate additional growers. Still, Midwestern winter growers, especially as they’re starting out, may struggle to find information that will allow them to optimize their winter salad mix production. Research has confirmed that babyleaf brassicas and lettuce are among the top choices for generating income with winter growing, but with so many choices on the market, it’s hard to know which varieties generate the best returns. 

For this project, we trialed 12 varieties of babyleaf brassicas, 2 varieties of lettuce, 1 lettuce mix, and 1 variety of arugula, seeding 12' blocks of each in unheated high tunnels in November and December of 2023. We harvested the greens in February and March, and found that our top-yielding varieties from these planting dates included three babyleaf brassicas: 'Carlton', 'Koji', and 'Vivid choi', and two lettuces: 'Green salad bowl' and 'Wildfire' lettuce mix.

Solution:

We trialed 8 varieties of cold tolerant babyleaf brassicas, 1 arugula, and 3 varieties of lettuce for salad mix by seeding each of these crops in our unheated high tunnels in 2.5’ x 12’ blocks on two different dates -- November 7 and December 5, 2023. For each planting date, all trial varieties were planted into the same tunnel. We chose trial varieties based on past experience, and input from other growers. We also choose varieties that have varying colors, textures, and shapes to create an appealing salad mix for customers. We’ve found that planting single varieties of brassicas and lettuce rather than mixes, and mixing the varieties post-harvest, allows for better yields and control for winter growing. Different varieties bolt at different times and some get freeze damage or disease while others remain unaffected. Our goal here was to find 4-6 varieties for optimal winter salad mix yields. 

To prepare beds for planting, we broadforked, use a power harrow or tilther, apply organic fertilizer or compost as needed according to our soil tests, then direct seeded the crops into our high tunnel beds with a Jang JP-5 seeder with every other hopper filled, seeding 6 rows per 2.5’ wide bed for all crops. After seeding, beds were irrigated with micro sprinklers and covered with row cover to aid germination. Row cover was removed after germination, and left off except during periods of <20 degree F weather. Below 10 degrees F, we will covered the crops with two layers of row cover. Most of our tunnels have automatic louvre vents at the peak of each endwall. We also roll up tunnel sides to vent the tunnels when the tunnel temperatures reach >80F. 

We aimed to get as many cuts as possible off of each planting, so we harvested crops above the growing tip for cut-and-come-again harvests, until bolting, at which point we harvested parts of the plants that were still tender enough for salad mix. We harvested with the Farmer’s Friend Quick-Cut Greens Harvester (https://www.farmersfriend.com/quick-cut-greens-harvester) when crops were sufficiently high quality and uniform, and otherwise cut by hand with serrated knives. We tracked the days to harvest for each crop, the number of harvests we were able to get throughout the winter season, the marketable yield (mass) per harvest, and the overall total mass we harvested per crop over the winter. 

Objectives:

1. Evaluate the relative yields of 8 babyleaf brassicas, 1 arugula, and 3 lettuce varieties planted in high tunnels on 2 different planting dates for winter harvests. 
2. Identify which 4-6 of these crops give the best yields for winter salad mix production.
3. Share findings through quarterly Community Growers Network trainings, our website and social media, and a conference presentation