Farmer-to-farmer sessions jump-start High Tunnel Production Conference
Over 100 growers shared their successes and failures raising specific crops in high tunnels on the first day of the two-day High Tunnel Production Conference at the Fireside Inn in West Lebanon, NH. The conference was a sellout with 120 registrations (and a waiting list) plus 30 speakers and vendors.
Professor Becky Sideman, department chair of Agriculture, Nutrition & Food Systems at the University of New Hampshire, deftly facilitated both back-to-back sessions: one on cucumbers, the other winter greens.
A show of hands established that more than half of the audience had taken a two-hour tour of the Edgewater Farm in nearby Plainfield, NH, earlier that day. The farm has approximately 70,000 square feet of poly greenhouses, mostly high tunnels, where ornamental bedding plants and greenhouse vegetables are grown. The family ownership team aims for “its long-term sustainability and compatibility with the natural biodynamics of our environment,” according to its website.
Conference attendees also appeared to embrace this approach, as shown both by their questions and informal conversations.
Sideman kicked off the cucumber session by asking audience members to call out the topics they’d most like to cover.
Growers’ experiences with when to plant cucumbers in the ground varied considerably, with heated high tunnels having a definite head start over unheated ones. Soil temperatures should be in the 65º to 70º range, many said. Most growers indicated they regularly prune their plants to ensure good airflow and also remove leaves that touch the soil, helping prevent disease. Regular harvesting is a must to maintain production.
Pests are a problem, and at both this session and others, entomologists urged growers to seek help from their land grant university’s lab where scientists can identify exactly what biotic (living or once-living) pests they’re facing. This allows growers to take appropriate action, knowing they’re not dealing with an abiotic condition, such as sunlight, water, air, soil, temperature and rocks.
Information from the University of Vermont is available at uvm.edu/-htunnel/factsheets.html. Add your email address to the UVM Tunnel Vision listserv to get a free quarterly newsletter by emailing cfrank@uvm.edu.
Growers have reached no consensus on the best ways to space their plants. Johnny’s Selected Seeds of Winslow, Maine, one of the 10 sponsoring vendors, has this advice in its 2026 catalog: “We highly recommend using parthenocarpic (asexual reproduction) varieties for greenhouse or tunnel production, as pollination can be challenging in a protected environment.”
The company also warns, “Thin-skinned varieties require more care to avoid abrasions, cuts and bruising and will dehydrate more quickly than field varieties.”
High Mowing Organic Seeds of Wolcott, VT, another sponsoring vendor, in its 2026 catalog warns that “thin-skinned cucumbers are especially affected by cucumber beetles and may require row cover.”
The relative profitability of selling produce was a hot-button topic. High-tunnel tomatoes, priced by the pound, are generally twice as profitable as cucumbers. Some growers recommended changing this ratio by pricing cucumbers by the piece rather than by the pound, upping their profitability.
Tony Lehouillier of Foote Brook Farm in West Johnson, VT, noted that he doesn’t raise cucumbers just to make a buck. “My kids will eat every cucumber they can get!” he said.
When Sideman started the Winter Greens session, she again asked attendees to call out their topics of greatest concern.
One grower with multiple high tunnels explained that he’s found “steaming” the best way to deal with high concentrations of weeds, including chickweed, which has tough, fibrous roots that can overwhelm inground winter greens.
High-tunnel steaming sterilizes soil when it’s bare, with no vegetation growing, killing weed seeds, soilborne pathogens (such as Pythium root rot) and pests. Growers use a specialized diesel- or kerosene-fueled machine equipped with a hose or “sock” system to inject steam under a tarp to heat the top layer of soil, killing unwanted organisms. Typically, only the first two inches of soil is heated to 160º.
One of the downsides of steaming is that the soil is effectively sterilized, and growers must take time and effort to restore fertility, especially in ways compatible with organic standards.
Beneficial microorganisms and organic matter, such as compost, must be reintroduced. Seven Springs Farm Supply of Check, VA, another sponsoring vendor, sells a High Tunnel Blend (one of its six fertilizer blends) designed for “high turnover, high production plantings.”
Other downsides are the high cost of the specialized machine, plus the fuel, labor costs and experience needed to do it correctly. Some conservation districts lend steamers to local farmers.
The conference was sponsored by UNH, UVM and the University of Maine, plus Northeast SARE. SARE has a bulletin (SARE.org/Topic-Rooms) on “High Tunnels and Other Season Extension Techniques.”
by Edith Tucker
