Hoophouses are useful tools for extending the summer growing season, and they also make it possible for farmers to meet the demand for local produce year-round.
Brad Jaeckel, manager of the Washington State University Organic Farm, said even an unheated structure can keep a Pacific Northwest farm busy through fall and winter.
Crops like broccoli, cabbage and bok choy, planted in June and July, can be harvested in the fall. Winter kale, chard and spinach, planted “pretty much every week,” are winter harvested. Green onions, transplanted in July, can over-winter for spring harvest.
Jaeckel said he believes in intensive production — “I pack in as much produce as I can” — scheduling different crops for seed-planting, transplanting or harvest every month of the year. During the coldest months, he puts low tunnels over the crops for additional protection, then removes them when it warms up.
He recommended growers record their planting times, varieties and yield so they can discover what works best for their growing conditions.
Spinach, for example, performs well in hoophouses, Jaeckel said.
“I call it the workhorse. It will expand your sales in winter and spring. There are so many different crops you can experiment with. Experimenting is the best way to get into this to see what’s going to work in your garden or farm.”
Other cool-season, frost-hardy crops are mustard greens, cabbages, carrots, beets, green onions, radishes, turnips, kale, chard, head and baby leaf lettuce and specialty greens like endive, claytonia and sorrel. All have different planting dates.
He recommended a couple of websites to help schedule them:
• Dave’s Garden — www.davesgarden.com/ — shows freeze and frost dates by ZIP code.
• A USDA website— www.planthardiness.ars.usda.gov/ — lists extreme minimum temperatures, also by ZIP code.
Direct seeding works best for lettuces, greens, spinach and radishes, but he recommended transplanting cabbage, bok choy, green onions, kale and chard.
Overwintering tomatoes “depends on your climate,” Jaeckel said. “We can’t in our hoophouse. With a heated greenhouse, you can keep them all winter long.”
A hoophouse structure can protect crops from poor growing conditions, but it does not protect against pests.
Snap traps work well against rodents, but “cats are a great option,” he said.
In Western Washington and other maritime climates, “You’re definitely going to see slugs,” he said. Extension educators and experienced gardeners can recommend effective control techniques.
Fungus and mold can be a big problem in brassicas and other crops, especially in late winter. Jaeckel recommended waiting until drier conditions and warmer temperatures arrive. Biochar and mineral balancing are other control tools.
When faced with soilborne diseases like tomato blight, he said, growers should not replant to an area that has been trouble before. Instead, they should rotate their plantings or graft onto blight-resistant rootstock.
A field walk from 2-3:30 p.m. Nov. 4 will highlight leafy green variety trials at Cloud Mountain Farm Center and at WSU Mount Vernon Research and Extension Center. Season extension, mechanized harvest and proposed changes to new safety rules will be discussed.