8 Supplies for Growing Tomatoes in a High Tunnel

Walking into a high tunnel filled with thriving, vertically trained tomato plants is the ultimate goal for many dedicated hobby farmers. While these protective structures offer an extended growing season and shelter from harsh weather, success hinges on having the right gear to manage the intensive microclimate. Equipping your tunnel with these eight essential supplies will transform your tomato harvest from a chaotic struggle into a streamlined, high-yielding success.

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Why High Tunnels Are Ideal for Tomato Crops

High tunnels act as a shield against the unpredictable elements of early spring and late autumn, effectively stretching the tomato growing season by several weeks on both ends. By trapping solar radiation, these unheated structures keep nighttime temperatures warmer and daytime temperatures optimal for rapid vegetative growth. This controlled environment allows hobby farmers to plant earlier in the spring and harvest well into the frost-prone days of autumn.

Beyond temperature control, the physical barrier of a high tunnel offers a crucial advantage: moisture management. Because rain cannot touch the tomato foliage, the risk of devastating fungal diseases like early blight and late blight is dramatically reduced. Controlling water intake solely through ground-level irrigation keeps the leaves dry and the plants remarkably healthy throughout their life cycle.

Preparing Your High Tunnel Soil for Planting

High tunnel soil works much harder than open-field soil because it is constantly warm and intensively cropped. Since natural rainfall does not reach the ground inside the tunnel, soluble salts can accumulate over time, and nutrients are depleted rapidly by heavy-feeding tomato plants. Preparing this soil requires a deliberate approach that focuses on restoring organic matter and ensuring deep, loose structure for expansive root systems.

Before transplanting, spread a two-inch layer of well-rotted compost across the planting beds to feed the soil microbiome and improve water retention. Use a broadfork to aerate the soil deeply without flipping the layers, preserving the delicate soil biology while breaking up hardpan. This structural prep ensures that your tomato roots can easily penetrate deep into the ground, accessing moisture and nutrients during the heat of summer.

Drip Irrigation – Rain Bird Gardener’s Drip Kit

Tomatoes require consistent, deep watering at the root zone to prevent blossom end rot and fruit cracking. Overhead watering inside a high tunnel is a recipe for disease, making a reliable drip irrigation system absolutely essential. The Rain Bird Gardener’s Drip Kit delivers water directly to the soil surface, minimizing evaporation and keeping the surrounding air humidity manageable.

This specific kit stands out because it is a complete, all-in-one solution designed for small-scale plots. It features clog-resistant emitters and flexible distribution tubing that can be easily customized to match your specific row layout. The rugged build quality ensures it handles the high-temperature environment of a summer tunnel without degrading or bursting under pressure.

• Coverage: Up to 75 plants or 150 square feet
• Tubing Type: 1/2-inch distribution tubing and 1/4-inch emitter tubing
• Compatibility: Standard outdoor garden hose or faucet connection

When setting up this system, keep in mind that it requires a pressure regulator and a simple faucet timer to run efficiently. You will need to lay the tubing close to the base of each tomato transplant and secure it with garden stakes so it does not shift during maintenance. It is the perfect fit for hobbyists managing up to 75 plants, but those with massive multi-tunnel setups will need to transition to commercial-grade drip tape.

Trellis Rollerhook – Paskal Tomato Rollerhook

Indeterminate tomatoes grown in a high tunnel can easily reach heights of fifteen feet or more, requiring a robust vertical support system. Standard tomato cages simply cannot handle this volume of growth, which is where the "lower and lean" trellising method comes in. The Paskal Tomato Rollerhook allows you to suspend your plants from an overhead wire and gradually lower them as they grow, keeping the harvest zone at a comfortable working height.

This product features a sturdy metal frame that clips securely onto your overhead support wire, pre-wound with high-tensile, UV-resistant twine. The integrated lock mechanism prevents the twine from slipping under the heavy weight of ripening fruit clusters, yet releases smoothly when you need to lower the plant. Its durable construction means you can reuse the metal hooks season after season, simply rewinding them with fresh twine.

• Twine Length: 36 feet of UV-resistant nylon twine
• Hook Material: Galvanized steel wire
• Application: Ideal for indeterminate tomato and cucumber varieties

To use these effectively, your high tunnel must have a strong overhead support structure, such as a metal conduit or thick steel wire, capable of holding hundreds of pounds of wet plant weight. There is a slight learning curve to the lowering and leaning process, as you must carefully coil the bare lower stems on the ground without snapping them. This system is indispensable for anyone growing high-yielding indeterminate varieties, but is unnecessary if you are growing short, bushy determinate tomatoes.

Shade Cloth – Coolaroo UV Block Shade Fabric

While tomatoes love warmth, extreme summer heat inside a high tunnel can cause flowers to drop, pollen to sterilize, and fruit to develop unsightly sunscald. A quality shade cloth acts as a shield, lowering the interior temperature by several degrees during the hottest parts of the day. The Coolaroo UV Block Shade Fabric provides the perfect balance of light transmission and heat reduction, ensuring photosynthesis continues without heat-stressing the crop.

This fabric is knitted from high-density polyethylene, making it highly resistant to tearing, fraying, and mold. The lightweight design allows it to be draped easily over the exterior of your high tunnel without collapsing the frame. Its breathable weave lets hot air escape upward, preventing the heat-trap effect that solid plastic covers can create during July and August heatwaves.

• Shade Rating: 30% to 40% UV block
• Material: High-density knitted polyethylene (HDPE)
• Sizing Options: Available in pre-cut sizes or bulk rolls

For tomato production, a 30% to 40% shade rating is the sweet spot; anything denser will restrict too much sunlight and stunt fruit development. You will need to secure the fabric tightly using heavy-duty tarp clips or bungee cords to prevent wind from catching it like a sail. This is a vital investment for southern or midwestern growers facing intense summer sun, but northern growers with mild summers may only need it during rare heatwaves.

Landscape Fabric – DeWitt Pro 5 Weed Barrier

Weeds thrive in the warm, irrigated environment of a high tunnel, competing with your tomatoes for water, nutrients, and root space. Hand-weeding inside a humid greenhouse is exhausting work that can easily be avoided with a physical barrier. The DeWitt Pro 5 Weed Barrier blocks sunlight from reaching weed seeds while keeping the tunnel floor clean, dry, and professional-looking.

What sets this fabric apart is its woven, needle-punched construction, which combines the durability of a woven fabric with the excellent water permeability of a non-woven barrier. This design allows water and liquid fertilizers to pass through effortlessly while preventing puddling on the surface. It is highly resistant to UV degradation, meaning it can withstand foot traffic and intense sunlight for multiple seasons without tearing or breaking down.

• Weight Class: 5 oz. heavy-duty commercial grade
• Material: Woven polypropylene needle-punched fabric
• Roll Widths: Available in 3-foot, 4-foot, and 6-foot widths

Before installing, ensure your beds are perfectly level and free of sharp rocks that could puncture the material. You must burn planting holes into the fabric using a propane torch or hot iron, as cutting it with scissors will cause the edges to fray over time. This heavy-duty barrier is a must-have for growers seeking a long-term, low-maintenance weed solution, but is less suitable for those who prefer to till their beds between every crop cycle.

Soil Thermometer – Luster Leaf 1618 Thermometer

Planting tomatoes too early into cold soil stunts their growth, purple-colors their leaves due to phosphorus lock-up, and delays your first harvest. Even if the air inside your high tunnel feels warm on a sunny spring afternoon, the soil temperature lags significantly behind. The Luster Leaf 1618 Soil Thermometer takes the guesswork out of transplanting by giving you an accurate reading of the root-zone temperature.

This analog thermometer features a solid aluminum casing and a clear, easy-to-read dial that displays temperatures in both Fahrenheit and Celsius. It is built to withstand the damp, gritty conditions of agricultural soil without fogging up or losing calibration. Because it requires no batteries, it is always ready to use when you step out to the tunnel on a chilly spring morning.

• Temperature Range: 0°F to 220°F (-10°C to 100°C)
• Probe Length: 5-inch aluminum stem
• Readout Type: Analog dial with clear zone markings

To get an accurate reading, insert the metal probe four to six inches deep into the soil where the tomato root ball will actually sit. Avoid forcing the probe into compacted soil, as this can bend the stem; instead, use a screwdriver to create a pilot hole if necessary. This simple tool is indispensable for eager growers pushing the limits of early spring planting, though it offers less value once summer heat is fully established.

Trellis Clips – Hydrofarm Tomato Trellis Clips

As your tomato plants climb toward the ceiling of your high tunnel, they need to be secured to their trellis twine every few inches. Wrapping the vine tightly around the string can restrict nutrient flow and bruise the delicate skin of the stem. Hydrofarm Tomato Trellis Clips solve this problem by gently locking the stem and the twine together in a spacious, supportive loop.

These 25mm clips feature a ventilated design that allows air to circulate around the stem, reducing the localized humidity that can harbor fungal pathogens. The heavy-duty plastic construction resists UV degradation and features a secure, quick-release latch that can be opened and closed with one hand. They are designed with small teeth that grip the trellis twine tightly, preventing the clip from sliding down under the weight of heavy fruit clusters.

• Clip Diameter: 25mm (approx. 1 inch)
• Material: UV-stabilized recycled polypropylene
• Pack Sizes: Available in packs of 100, 500, or 1000

When applying these clips, always place them directly beneath a sturdy leaf branch so the node supports the weight of the plant as it grows. You will need hundreds of these for a standard high tunnel, so buying them in bulk is highly recommended. While they are incredibly easy to use, you must take the time to sanitize them in a mild bleach solution at the end of the season to prevent carrying diseases over to next year’s crop.

Tomato Fertilizer – Espoma Organic Tomato-Tone

Tomatoes are incredibly heavy feeders that require a steady supply of nitrogen, phosphorus, potassium, and micronutrients to produce abundant fruit. In the confined, high-output environment of a high tunnel, soil nutrients are depleted rapidly. Espoma Organic Tomato-Tone is formulated specifically for nightshades, delivering a balanced nutrient profile that supports strong root development and heavy fruit set.

This organic fertilizer stands out because it contains 8% calcium, which is the critical nutrient needed to prevent blossom end rot in rapidly growing tomatoes. It is enriched with Espoma’s proprietary Bio-tone microbes, which actively work to improve soil structure and make nutrients more bioavailable to the plant roots. The slow-release formula ensures your plants receive consistent nutrition over several weeks without the risk of chemical burns or excessive foliage growth at the expense of fruit.

• NPK Ratio: 3-4-6 balanced organic formula
• Key Ingredients: Feather meal, poultry manure, bone meal, calcium carbonate
• Inoculant: Bio-tone microbes for root stimulation

For best results, mix Tomato-Tone into the planting hole at transplanting, and then top-dress around the base of the plants every two weeks once fruit begins to set. Because it is an organic product, it relies on soil moisture and active soil biology to break down, meaning it works best in warm, living soils. This is the ultimate choice for growers committed to organic practices, though those looking for an instant, water-soluble quick fix may prefer liquid synthetic options.

Pruning Shears – Felco 2 Classic Hand Pruner

High tunnel tomato production requires constant pruning to maintain a single stem, remove unproductive lower foliage, and maximize airflow. Using dull shears or pinching suckers with your fingers can tear the plant’s skin, leaving jagged wounds that invite disease. The Felco 2 Classic Hand Pruner delivers clean, razor-sharp bypass cuts that heal quickly, keeping your plants healthy and stress-free.

This legendary tool features hardened steel blades and a forged aluminum alloy handle, offering a perfect balance of strength and lightweight comfort. The adjustable alignment system ensures a precise cut every time, while the integrated sap groove prevents the blades from sticking when cutting through gummy tomato stems. Every single part on a Felco 2 is replaceable, making this a lifetime investment rather than a disposable seasonal purchase.

• Cutting Capacity: Up to 1-inch diameter stems
• Blade Material: High-quality hardened steel
• Handle Type: Forged aluminum with non-slip grip cushions

Because tomato sap is highly sticky and can carry viral pathogens like Tobacco Mosaic Virus, you must wipe the blades clean and sanitize them with rubbing alcohol between plants. The bypass design is perfect for live green wood and soft tomato stems, but should not be used on dry, woody branches which can nick the blade. This is the premier choice for any grower who values tool longevity and ergonomic comfort during long hours of tunnel maintenance.

Managing Ventilation and Humidity in the Tunnel

Managing the climate inside a high tunnel is a daily balancing act that directly impacts your tomato health and yield. Because transpiration from large tomato plants releases massive amounts of moisture into the air, humidity levels inside a closed tunnel can quickly skyrocket. This stagnant, humid air is a breeding ground for devastating diseases like powdery mildew, leaf mold, and grey mold.

To combat this, prioritize ventilation by rolling up the side curtains and opening the end-wall doors as soon as morning temperatures rise above 60°F. Creating a cross-breeze is essential for moving humid air out of the canopy and bringing in fresh carbon dioxide for photosynthesis. On calm, humid days, installing simple solar-powered or electric circulation fans can provide the necessary air movement to keep leaves dry and promote healthy transpiration.

Maximizing Your High Tunnel Tomato Yields

Achieving maximum tomato yields in a high tunnel requires combining the right supplies with disciplined cultural practices. Focus on training your plants to a single leader by consistently removing side suckers every week before they grow larger than a pencil. This directs all the plant’s energy into upward growth and fruit development rather than dense, unproductive foliage.

As the plants climb, utilize your rollerhooks to lower the vines, keeping the active ripening clusters within arm’s reach while coiling the bare lower stems neatly on the landscape fabric. Combine this vertical training with consistent, automated drip irrigation and regular organic feeding to prevent stress-induced blossom drop. By maintaining this tight control over water, nutrients, and airflow, your high tunnel will reward you with an abundance of pristine, market-quality tomatoes from spring until the first hard freeze.

Investing in high-quality, task-specific supplies transforms the challenging environment of a high tunnel into a highly productive tomato haven. With the right tools for support, irrigation, and climate control, you can look forward to a streamlined growing season and a spectacular harvest.