8 Pieces of Gear for Winter Gardening in High Tunnels

Outside the high tunnel, frost hardens the mud while icy winds sweep across the beds, yet inside, row covers shield bright ribbons of winter spinach. Successfully growing crops through the coldest months relies on creating reliable layers of protection inside an unheated structure. Equipping a high tunnel with the right gear transforms a passive plastic shelter into a resilient, micro-climate-controlled winter garden.

Disclosure: As an Amazon Associate, this site earns from qualifying purchases. Thank you!

Setting Up Your High Tunnel for Winter Success

Winter high tunnel production is not simply about keeping frozen air out. It is about capturing daytime solar thermal radiation, trapping it in the soil, and releasing it slowly overnight. An unheated high tunnel generally provides one hardiness zone of temperature protection, but adding secondary structures inside the house creates micro-climates capable of keeping hardy greens alive through sub-zero nights.

Structure layout determines how effectively heat is retained. Placing beds along a North-South axis maximizes winter sun exposure across all rows, avoiding shade cast by structural hip-boards or purlins. Pathways should be kept narrow to dedicate maximum thermal mass—the moist, dark soil of your growing beds—to heat absorption during peak daylight hours.

Preparing the high tunnel before deep winter sets in requires sealing air leaks along the perimeter baseboards and ensuring smooth ventilation access. Hardware, irrigation lines, and structural supports must be fully installed and tested while temperatures remain above freezing. Waiting until freezing conditions arrive makes assembly difficult and increases the risk of damaging dormant crops.

Row Cover – Agribon AG-50 Frost Protection

Row covers act as the primary blanket inside a winter high tunnel. While thin row covers work well for spring insect barriers, winter production demands a heavy-duty fabric that traps heat rising from the soil. Placing extra coverage directly over crops creates a protected environment inside the larger structure, preventing frost burn on tender leaf margins.

Agribon AG-50 offers extra-heavy weight construction weighing 1.5 oz/yd², providing freeze protection down to 24°F to 26°F by trapping heat around plant foliage. This heavy material delivers an added temperature buffer of 6°F to 8°F under the high tunnel plastic, which makes the difference between surviving and dying during deep cold snaps.

• Material: Non-woven spunbond polypropylene
• Light Transmission: 50%
• Best Uses: Deep winter frost protection, low-tunnel inner covers, freeze protection for cold-hardy greens

The reduced light transmission means this fabric should be pulled back during sunny winter days to maximize photosynthesis. The thick fabric absorbs moisture from soil evaporation, making it heavier when wet, so secure anchoring is necessary to keep it from slipping off beds. Growers in Zones 4 through 6 will find AG-50 essential, while growers in milder winter zones may find lighter options like AG-30 sufficient.

Wire Hoops – Johnny’s 9-Gauge Hoop Supports

Draping heavy row covers directly onto foliage causes condensation to transfer moisture onto leaves, leading to ice crystals and leaf tissue damage. Wire hoops establish a rigid frame over crop beds, holding fabrics elevated off the plants. This airspace creates an insulating thermal cushion between the row cover and the crop canopy.

Johnny’s 9-Gauge Wire Hoops feature pre-bent galvanized steel wire engineered specifically for standard 30-inch to 36-inch farm beds. Unlike flimsy garden-center wires that sag under heavy fabric, 9-gauge steel wire holds its structural arch under damp row covers and light condensation weight without bending inward.

• Wire Diameter: 9-gauge galvanized steel
• Height Above Bed: Approximately 12 to 18 inches when installed
• Compatibility: Fits standard 30-inch to 36-inch raised or flat beds

Installing hoops requires pushing the ends 6 to 8 inches into the soil along the bed edges, spaced roughly 4 to 5 feet apart down the row. Soil that freezes deep along perimeter beds can make late-season hoop adjustments difficult, so press hoops into position before the ground hardens. These supports work best for low-growing crops like spinach, lettuce, kale, and root crops, but are not designed for tall, overwintered fruiting plants.

Space Heater – Mr. Heater Big Buddy Propane

Passive heat and double-layer covers handle routine winter nights, but extreme polar plunges demand emergency back-up heating. An unvented portable heater provides a quick burst of warmth inside a high tunnel to prevent soil and crop surfaces from dropping past critical freeze thresholds.

The Mr. Heater Big Buddy Propane Heater produces up to 18,000 BTUs per hour, making it capable of heating spaces up to 450 square feet during cold emergencies. It runs off twin 1-pound propane cylinders or connects directly to a 20-pound propane tank using an optional hose with an integrated fuel filter.

• Heat Output: 4,000 / 9,000 / 18,000 BTU settings
• Safety Features: Low-oxygen shutoff system (ODS) and tip-over safety switch
• Power Source: Dual 1 lb propane cylinders or remote 20 lb tank connection

Burning propane generates moisture as a byproduct, increasing indoor air humidity inside an enclosed high tunnel. Position the unit on a flat, non-combustible surface clear of plastic walls, row cover edges, and overhead drip lines. This heater serves well as a supplemental heat source for small-scale growers during arctic cold fronts, but is not designed for continuous primary heating in large commercial structures.

Managing Humidity and Ventilation on Sunny Days

High humidity is a persistent challenge in winter high tunnel management. Cold air holds less moisture than warm air, causing water vapor from soil evaporation and plant transpiration to collect on plastic walls and inner row covers. High humidity combined with cool temperatures creates ideal conditions for fungal pathogens like grey mold (Botrytis cinerea) and downy mildew.

Managing humidity requires opening vents on clear, sunny mornings, even when ambient outdoor temperatures remain cold. Solar heat rapidly elevates high tunnel temperatures, causing air to expand and absorb moisture. Cracking side roll-ups or end-wall vents allows hot, damp air to escape while drawing in drier outdoor air before moisture drips onto crops.

Ventilation timing is critical during winter days. Vents should open late enough in the morning to prevent chilling crops, yet early enough to clear condensation off the inner plastic surface. All vents must be fully closed by mid-to-late afternoon to trap residual thermal heat in the bed soil before outdoor temperatures plunge at sunset.

Digital Monitor – Govee Wireless Thermometer

Real-time micro-climate monitoring prevents crop damage caused by sudden freeze events or unexpected solar overheating. A reliable wireless monitor tracks indoor conditions without requiring growers to constantly unclip high tunnel doors or disturb inner row covers.

The Govee Wireless Thermometer Hygro-Thermometer uses a Swiss-made sensor to deliver accurate temperature and humidity readings directly to a smartphone app via Bluetooth or Wi-Fi. It records continuous data logs, generating clear daily graphs that pinpoint temperature drops and moisture spikes.

• Accuracy: ±0.5°F for temperature, ±3% for relative humidity
• Connectivity: Bluetooth with optional Wi-Fi gateway integration
• Alert System: Instant app notifications for custom temperature and humidity thresholds

Place the sensor at plant canopy level under inner row covers rather than high on the tunnel frame to capture actual micro-climate data. Mount the device out of direct irrigation spray and shielded from direct sunlight to prevent false high readings. This monitor is essential for part-time farmers who manage high tunnels around off-farm work hours, but requires a nearby Wi-Fi network for remote access outside Bluetooth range.

Soil Thermometer – Reotemp Heavy Duty Probe

Air temperature inside a high tunnel fluctuates rapidly with sunlight, but soil temperature changes slowly and governs root activity, nutrient uptake, and seed germination. Tracking soil conditions helps growers know when crops enter winter dormancy and when root zones are warm enough to absorb water.

The Reotemp Heavy Duty Soil Thermometer features a rugged stainless steel stem and a sealed, easy-to-read dial display. The 1/4-inch diameter stem resists bending when inserted into firm, compacted soil, while the glass-covered dial prevents fogging in humid high tunnel environments.

• Stem Length: 12 inches to 24 inches (12-inch recommended for topsoil monitoring)
• Dial Diameter: 2 inches with hermetically sealed glass
• Temperature Range: 0°F to 220°F (or custom soil ranges)

Insert the probe stem 4 to 6 inches deep directly into crop beds, as this depth represents the primary root zone for greens and salad crops. Leave the thermometer in place for at least 60 seconds to allow the mechanical bi-metal coil to stabilize before taking a reading. This manual tool is ideal for verifying root zone conditions, though it lacks digital logging capabilities.

Vent Opener – Bayliss Autovent MK7 Spring

Winter days can shift rapidly from overcast to bright sun, causing high tunnel temperatures to spike above 80°F within minutes even on cold days. Automatic vent openers manage heat build-up passively, opening end-wall louvers or peak vents without requiring electricity or manual intervention.

The Bayliss Autovent MK7 Spring uses a mineral-wax-filled cylinder that expands when warmed, pushing a mechanical lever arm to open peak vents or louvers. As temperatures cool, the wax contracts, and heavy-duty return springs close the vent tightly against cold winter wind drafts.

• Lifting Capacity: Opens vents weighing up to 12 lbs
• Opening Range: Begins opening between 60°F and 75°F (adjustable set-point)
• Power Source: Solar thermal expansion (100% non-electric)

Thread the wax cylinder in or out to set the desired opening temperature threshold for winter production. Protect the unit by unhooking the cylinder during deep zero-degree weather if temperatures drop below the mechanism’s safe storage range. This autovent is perfect for top peak vents and end-wall louvers, but lacks the lifting strength required for heavy, full-length roll-up sidewalls.

Drip Irrigation – DripWorks High Tunnel System

Overhead watering in a winter high tunnel wet plant foliage and spikes air humidity, inviting crop diseases. Drip irrigation delivers water directly to root zones beneath row covers, keeping plant leaves completely dry and conserving soil warmth.

The DripWorks High Tunnel Drip Kit includes 1/2-inch mainlines and drip tape with 12-inch emitter spacing, supplying uniform moisture directly to high-density vegetable beds. The kit features an integrated pressure regulator and filter assembly that connects directly to a standard garden hose or frost-free hydrant.

• Operating Pressure: Regulated to 15 PSI
• Emitter Spacing: 12 inches along drip tape lines
• Kit Inclusions: Mainline tubing, drip tape, pressure regulator, filter, shut-off valves

Winter irrigation needs drop significantly compared to summer; watering once every 10 to 14 days is often sufficient for cold-season greens. Lines must be completely drained or purged with compressed air if unheated tunnel temperatures drop low enough to freeze water inside the main manifold. Drip systems work best for raised or flat bed layouts, but require careful management to avoid overwatering cold, slow-draining winter soils.

Harvest Snips – ARS 300L Precision Shears

Harvesting cold-hardy greens in freezing or near-freezing conditions requires sharp, precise tools. Dull blades crush frozen plant stems, damaging crown tissue and reducing the shelf life of harvested greens.

ARS 300L Precision Shears feature high-carbon steel blades ground to a razor-sharp edge, allowing rapid, clean cuts through thick spinach stems and delicate lettuce crowns. Their lightweight, spring-loaded design reduces hand fatigue when working in cold, damp conditions with gloved hands.

• Blade Material: High-carbon steel with nickel plating
• Overall Length: 7.5 inches
• Design Features: Non-slip grips, coil return spring, secure blade lock

Keep blades clean and wiped dry after every harvest, applying a light coat of food-grade oil to prevent surface rust caused by sap and moisture. Avoid using these delicate shears for woody stems, thick root pruning, or heavy wire cutting, as this can nick the edge. These snips excel at rapid harvest of cut-and-come-again winter greens and salad mixes.

Daily Routines for Cold Climate High Tunnels

Managing a high tunnel in winter depends on a steady daily routine built around sunlight and temperature shifts. Morning checks start by evaluating the internal air and soil temperatures. On clear days, inner row covers should be pulled back once air under the main tunnel warms up, exposing crops to direct sunlight and encouraging photosynthetically active radiation absorption.

Midday management centers on ventilation and moisture control. If high tunnel walls show heavy condensation or temperatures rise above 65°F, open end-wall vents slightly to vent humid air. Check soil moisture manually by inserting a finger two inches into crop beds; winter crops require light watering only when the soil surface feels dry to the touch.

Late afternoon routines focus on trapping thermal energy before sunset. Close all external vents and roll-up sides while the sun is still striking the plastic. Pull heavy row covers back over wire hoops before outdoor temperatures drop rapidly, sealing the edges firmly against bed soil to trap radiant heat through the night.

How to Store Winter Gear When Spring Arrives

Proper seasonal care and storage extend the operational life of winter gardening equipment. As spring temperatures rise and inner frost protection is no longer needed, remove row covers on a dry, sunny day. Shake off loose soil, check for tears that need mending, fold covers loosely, and store them in sealed, rodent-proof bins to prevent nesting damage over summer.

Pull wire hoops from crop beds once freezing risks pass. Wipe off clinging mud, check for bend rust, and bundle hoops together with heavy twine or zip-ties grouped by size. Storing hoops vertically off the ground prevents corrosion and keeps them straight and ready for autumn re-installation.

Drain all drip irrigation manifolds, pressure regulators, and lines before storing them away from hot summer sun, which degrades thin-walled drip tape. Service heaters by cleaning burners, disconnecting fuel hoses, and storing units in clean, dry sheds. Remove wax cylinders from automatic vent openers if summer temperatures inside peak vents exceed maximum safety thresholds, storing them in cool locations to protect the seals.

Outfitting a high tunnel with targeted frost protection, monitoring tools, and specialized ventilation gear ensures stable production through the coldest months. Understanding how each piece of equipment contributes to temperature retention and moisture control allows small-scale growers to manage micro-climates efficiently. With the proper tools and daily management, cold-hardy crops will thrive through deep winter and deliver fresh, high-quality harvests straight into spring.