Tag Archive for: High Tunnel

By Audrey Kolde, NCAT Agriculture Specialist 

For many vegetable growers in climate zones nine and warmer, like where I live in Louisiana, summer brings a familiar yet challenging routine. In May and June, those long sunny days and warm soils fuel vibrant growth. But July and August bring real heat, and suddenly it feels like we’re all moving in slow motion. Tomato pollen becomes infertile, peppers get sunscald, and beans struggle to breathe under high ozone levels.

Two caterpillar tunnels at the VEGGI Farmers Cooperative, with sweet potatoes growing between them. Photo: Audrey Kolde

This seasonal slowdown is a natural part of the farm rhythm and even needed for certain farm goals like cover cropping, infrastructure projects, planning, or that vacation you need. But sometimes you may need to push a crop a bit longer, bridge a production gap, or protect sensitive varieties. That’s where shade becomes a useful tool. 

Though shade cloth has traditionally been used over greenhouses, this clever solution is making its way into open fields, offering an invaluable respite from the sun’s harsh rays. In the fields, the crops basking in too much sunlight can suffer from sunburn, absorbing more light than they can safely use, leading to heat exhaustion and even to their leaves “fainting” from the stress! 

Shade cloth can reduce solar radiation that causes these problems. The even light the net creates prevents overheating, flower drop, localized burn spots on peppers, and cracking on tomatoes when temperatures soar past 90°F.  

Making an Investment 

Now, before we get too excited, let’s talk about costs. Shade cloth can be an investment, with costs dependent on factors such as shading percentage, material, UV stabilization, and whether you opt for knitted or woven. For those covering large areas, costs can escalate quickly, especially when you factor in the necessary hardware, posts, and tensioning systems. But here’s the silver lining: the initial investment often pays off. When the scorching sun brings sunscald, blossom drop, bittering, and reduced fruit set, the economic losses can quickly outweigh the cost of shade structures. Even a minor reduction in plant stress can mean steadier yields, superior quality, and an extended harvest window, offering substantial returns during the most unpredictable parts of the growing season. 

When purchasing shade cloth, cut-to-length pieces work well for first-time users, small-scale growers, or trial runs, while bulk rolls are ideal for farms managing multiple blocks or constructing several shelters. Always seek suppliers who offer UV-stabilized materials, transparent warranty terms, and consistent mesh quality. A reputable supplier will also give you comprehensive specifications, including the actual shade percentage, expected lifespan, airflow properties, and whether the cloth is knitted (which tends to be more durable) or woven (stiffer but may fray). Because shade cloth is an investment, you’re better off using it for your highest-value crops that bring you the greatest return on investment.  

A Versatile Tool

When I first purchased shade cloth, my main goal was to cool down my greenhouse. However, it didn’t take long for me to recognize that my field needed it just as desperately. I explored which setups stood strong in the face of wind and were worth my efforts. What astonished me the most was the sheer versatility of shade cloth – it’s like a chameleon that adapts perfectly when paired with the right structure and crop. 

Shade cloth over a caterpillar tunnel frame protects vulnerable vegetables. Photo: NCAT

I began using shade cloth on low tunnels because I already had some hoops from my winter growing endeavors. This system revealed itself to be one of the simplest and most cost-effective options for shading crops in the field. With a little creativity, you can repurpose wire hoops, PVC pipe, or conduit bent into arches to create tunnels, draping the shade cloth directly over the top and securing it with sandbags, landscape staples, or snap-on clips. The beauty of this system lies in its accessibility; most growers already have the materials on hand, which helps keep costs low and waste to a minimum. However, it’s crucial to ensure proper anchoring and attachment, especially during high winds or sudden summer storms. A few sturdy clips and weighing down the edges can make all the difference in preventing the cloth from lifting or tearing.  

Low tunnels are particularly effective for crops like lettuce, brassicas, cucumbers, herbs, and young transplants. But they’re not without their challenges! One downside is that low tunnels can trap excessive heat when ventilation is restricted, which leads to stressed crops and increased humidity. The key is to use a lighter shade cloth, keep the sides open, and promote good airflow. In hotter climates, opting for lighter-colored or aluminized cloth can reflect heat, while darker cloth might trap it. And let’s not forget about tension! Loose cloth that flaps in the wind wears out quickly, so ensuring it’s snugly stretched over the hoops not only enhances durability but also stabilizes the structure.  

Suspension Systems 

Thinking bigger, I expanded to a suspension-style system that stretched shade cloth over multiple crop rows. This setup involved T-posts, bamboo, EMT conduit, and even 4” x 4” wooden posts along the bed edges. I strung paracord, wire, or greenhouse twine between the posts like clothesline. Achieving strong tension here is essential, and a ratchet strap proved invaluable for getting that perfect tautness. I found that upgrading to 10-foot T-posts provided the resistance I needed for this taller structure. Clipping and zip-tying the shade cloth to the frame resulted in a spacious, airy canopy that kept me cool while I worked beneath it.  

This design not only minimized costs by reusing existing materials but also excelled during afternoon showers, provided I anchored it properly! Deep-set posts, taut lines, and secure attachments are vital to withstand intense rainfall or sudden gusts. And trust me: hurricane winds and sail-like canopies are a recipe for disaster, so make sure to take it down when preparing for a big storm.  

This canopy-style shade works wonders for summer greens, peppers, tomatoes, ginger, and turmeric, due to its excellent ventilation. Inadequate airflow can raise humidity and increase disease risks. The main challenge revolves around maintaining tension. Sagging cloth can create pockets that trap water and wind, putting the structure at risk. Choosing the right shade percentage is crucial, too. If you overshade your crops, you risk hindering their photosynthesis when they need it the most. But with the right setup, this system stands out as one of the most efficient ways to shade multiple beds simultaneously.  

Another effective method is to stretch shade cloth directly over existing trellises. I found that laying shade cloth horizontally above trellis lines or cattle panels—angling it toward the west to buffer that harsh afternoon sun—works like a charm. Try this approach on tomato stakes, Florida-weave systems, and cucumber tunnels. For growers seeking a quick, budget-friendly way to protect sunscald-prone crops like tomatoes, peppers, and cucumbers, this is an excellent starting point.  

Nature’s Solution 

Luffa grows over trellises at Inglewood Farm, with lettuce (not visible) planted beneath. Photo: Audrey Kolde

Stratification, i.e., the natural layering of vegetation, creates cooler, buffered microclimates, which farms can utilize. This is why combining shade cloth with living plants has become one of my favorite agroecological strategies. I plant tall crops such as sunflowers, okra, sorghum-sudan grass, or trellised crops (my favorites are cucuzza, luffa, and cucumbers) to create a vertical, layered habitat that naturally cools the soil and protects sensitive crops. While these plants are growing to full size, I use shade cloth temporarily and then remove it once the living canopy takes over. Mimicking natural ecosystems on the farm can reduce your farm’s plastic use, but it requires close monitoring to avoid competition for water and nutrients. Living shade is particularly effective in mixed perennial-annual systems or on farms seeking long-term ecological resilience. Shade trees and agroforestry systems can provide a more permanent form of stratification, creating microclimate buffers while adding habitat and carbon storage.  

In addition to living shade, there are many other options for complementing or replacing traditional shade cloth. Greenhouses can achieve similar effects by painting the greenhouse with a limewash to diffuse sunlight, thereby reducing heat without adding physical structures. Some farmers experiment with natural-fiber materials like hemp cloth as biodegradable shading options. Drawing from all these tools, living systems, structural shade, and material alternatives, it is possible to design a shade strategy that supports both crop health and long-term farm sustainability. 

Related Resources

ATTRA Publication: Season Extension Techniques for Market Gardeners

ATTRA Blog: Agroforestry and Agrivoltaics: Two Appropriate Technologies for Smart Shade on Farms

This blog is produced by the National Center for Appropriate Technology through the ATTRA Sustainable Agriculture program, under a cooperative agreement with USDA Rural Development. ATTRA.NCAT.ORG.

By Chris Lent, NCAT Agriculture Specialist 

It’s a chilly morning in late March and the seedling house heater kicked on several times overnight to keep the plants happy. The skies are cloudy as you get the kids to the bus and run to the hardware store. On the way back to the farm after your errands, you notice that the clouds are gone, the strength of the late morning sun taking you by surprise after what had been a cool late winter. Oh no… the seedling house! You rush home to make sure your plants aren’t getting cooked.  

If you can relate to this scenario, it may be time to consider the benefits of automating the control points in your high tunnels and seedling houses. Those benefits include more consistent watering, less severe temperature swings, better production results, labor and energy savings, and better work-life balance.  

The tools and systems available for automation are many and varied. The size of your farm, business goals, and lifestyle goals can all help inform decisions on the type and level of automation to move toward on your farm. A good first step is to identify components in your high tunnels and greenhouses that can be automated. For example:

  • Heating (hot air units, boilers, hot water heaters)
  • Cooling (ventilation fans, pad and fan cooling units, A/C) 
  • Humidity control (fans, roll-up sides, ridge vents, fog) 
  • Air circulation (horizontal airflow fans) 
  • Irrigation (pumps and valves) 
  • Lighting 
  • Thermal control (shade, screens, thermal blankets) 

For many years, the default automation used in high tunnels and greenhouses on small to midsize farms relied on dedicated controls. Dedicated controls operate only one piece of equipment at a time. Examples of dedicated controls include in-line irrigation timers and individual thermostats for heating units or fans. These controls require monitoring and manual resetting as weather conditions change. 

Integrated control systems are a newer alternative to dedicated controls. These systems use feedback from sensors and electronic processing to control the frequence and sequence of equipment operation to keep a tunnel or greenhouse very close to temperature and humidity set points. Once installed and programmed, they work autonomously. Integrated controls can operate motors for roll-up sides, ventilation fans, and heating units cooperatively with little manual input.  

An integrated control system for heating and ventilating a seedling house on a farm in PA. Photo: Chris Lent, NCAT

Integrated automation systems can save costs in labor, decrease the risk of losing a crop, and save energy. There are many brands and styles of integrated control systems, so it can be time-consuming to search for the best option. If you have an established relationship with a trusted greenhouse supplier, they can help guide decisions on DIY automation projects.  

Previously, it was primarily large-scale producers who used these kinds of systems, but there are now companies that offer design and installation guidance for smaller scale integrated automation systems. Some brands have screens on the equipment to enable the user to enter set points, while other brands rely entirely on Wi-Fi and a device app for user interface. These systems can range in price between $2,000 and $4,000 per tunnel or greenhouse depending on the complexity and the brand of the system. Some companies also lease system components to the farmer and will automatically replace parts of the system if they fail. This lowers upfront costs and decreases hassle for the farmer.   

Fully integrated systems are something to aspire to, but most growers automate irrigation control and temperature and humidity control separately. For irrigation, a good example of a dedicated control is the simple, low-cost ($10 to $20) controls for irrigation in the form of in-line timers. You can purchase these from greenhouse supply companies, but garden centers and hardware stores also usually carry some version of these devices. They allow you to set an irrigation line to water for a certain amount of time, then automatically shut off.  

A dedicated in-line irrigation timer requires manual setting for each watering event in a tunnel. Photo: Chris Lent, NCAT

Battery powered digital programmable irrigation timers are available as well and can be sized to the irrigation line. These can cost from $100 to $150 for control over a single irrigation zone but give the grower much more control, and once programmed, they can give you freedom from the task of turning water on and off manually. Multi-zone digital controllers allow growers to control multiple valves in a more customized irrigation system.   

Some tips to keep in mind for automation: 

  • Assess the need first: Count the number of heating, cooling, and ventilation units you will need to control and estimate the cost to manually control these. 
  • Get advice and pricing from greenhouse suppliers and companies that focus on greenhouse automation. 
  • Get quality sensors with solar guards and place them near the crop. 
  • Install an ambient air and soil monitoring system to monitor all growing conditions and send notices to your phone. 
  • Consider installing camera monitors so you can visually check conditions in a tunnel or greenhouse on your phone. 
  • Make sure your infrastructure is compatible with the automation system you want. Does it require electricity and reliable internet to work? 

Automating the environmental controls in high tunnels and greenhouses can improve productivity and give some freedom from everyday tasks, but it doesn’t mean growers can become Ron Popeil and “set it and forget it.”  Frequent visits to monitor high tunnel conditions and the health of a crop are still necessary. However, being able to rely on automatic control systems to manage conditions in a tunnel or greenhouse and being able to check those conditions and receive alerts from anywhere gives peace of mind when you decide to step off the farm.   

Ultimately, choosing the right level of automation is about finding a balance that supports both your crops and your daily life. Whether you start with a few dedicated controls or invest in a fully integrated system, each step toward automation can reduce stress, protect your plants, and make your operation more resilient. Automation systems can’t fully replace a grower’s attention and experience, but they can serve as a reliable partner in maintaining optimal conditions, preventing costly mistakes, and creating more time for the many other demands of running a farm. 

Related ATTRA Resources: 

Season Extension Techniques for Market Gardeners 

Sustainable Season Extension: Considerations for Design 

Purchasing and Siting a High Tunnel to Extend the Growing Season 

Organic Greenhouse Vegetable Production 

Additional Resources: 

Greenhouse and High tunnel suppliers: 

High Tunnels Supplier Directory – HighTunnels.org 

Integrated automation companies: 

Link4 Controllers | Link4 Controls 

Orisha | Get Your Tomato Yields Up! 

Agrowtek Inc. :: Grow Controls for Greenhouses, Hydroponics & Indoor Growing

This blog is produced by the National Center for Appropriate Technology through the ATTRA Sustainable Agriculture program, under a cooperative agreement with USDA Rural Development. ATTRA.NCAT.ORG.