Tag Archive for: Risk Management

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 Andy Pressman, NCAT Sustainable Agriculture Program Director

“Homegrown tomatoes, homegrown tomatoes,
What’d life be without homegrown tomatoes?
Only two things that money can’t buy
And that’s true love and homegrown tomatoes.”

– Guy Clark, Homegrown Tomatoes

Listen to a clip of “Homegrown Tomatoes” by Guy Clark

The author’s daughter enjoying a homegrown tomato.

It sure is hard to imagine life without homegrown tomatoes. For some, like American folk singer Guy Clark, it is well worth the wait over the winter months for a sun-ripened tomato fresh off the vine, and for the experience of first biting into one and feeling that rush of flavor as it explodes in your mouth. This moment of joy is not limited to gardeners—anyone can seek out these precious, homegrown flavors from farmers who grow tomatoes skillfully and with great care.

Tomatoes are a staple summer crop for many diversified farms: high-value, in-demand, and, when conditions are right, highly productive. But as summers grow hotter and more unpredictable, even this dependable crop can show signs of stress. Blossom drop, sunscald, delayed or uneven ripening, and declines in yield are symptoms caused by intense heat.

Whether you’re selling at farmers markets, through CSA shares, or to wholesale accounts, heat stress in tomato production can quickly translate into lost income. With the right strategies, you can mitigate heat-related issues and maintain healthy, productive plants, even at the height of summer. Read on for common heat-related issues and how to solve them.

Fruit Set and Blossom Drop

Heat can impede fruit set when daytime highs are consistently over 90°F and nighttime temperatures stay above 70°F. Blossoms can drop and pollen can become less viable as the plant shifts from reproductive to survival mode. Choosing heat-tolerant varieties and staggering plantings to avoid peak summer stress, including planting early in high tunnels, can reduce blossom drop. Using hoops and shade cloth in the field can reduce the sun’s intensity. Managing soil temperature and moisture by utilizing practices such as drip irrigation and mulching can also help retain flowers.

Close-up of a tomato blossom. Photo credit: Nina Prater.

Pollination

Fruit deformities can result from a lack of pollination. Planting pollinator habitats in and around tomato plantings can increase pollination from native pollinators. It’s also a good idea to limit insecticide use (even organic-approved insecticides) during bloom periods. Hand-pollinating plants can improve pollination rates, especially in high tunnels. Applying a kelp or seaweed fertilizer as a foliar spray during early flowering also helps mitigate heat-related stress that impacts pollination and causes misshapen fruits.

Sunscald

Sunscald on tomatoes occurs when the fruit is exposed to intense sun, especially after the plants are pruned and leaf cover is reduced. Sunscald causes the fruit to develop leathery white or gray patches on the skin that make it unmarketable. Maintaining leaf canopy during periods of extreme heat by limiting pruning and sucker removal can reduce sunscald. Trellising can assist in providing more leaf canopy, while also assisting with airflow. And, as with blossom drop, utilizing shade techniques in high tunnels or in the field can reduce the risk of sunscald during periods of intense heat.

Ripening Issues and Yellow Shouldering

Extended periods of high temperatures can cause uneven or delayed ripening, and can also cause the fruit to exhibit green or yellow tops, known as yellow shouldering. Managing potassium availability in the soil can help prevent these issues. Use soil tests to determine potassium levels and apply amendments, such as kelp meal, as needed. Adding too much nitrogen, especially late in the season, can prolong vegetative growth, which slows fruit ripening. If daytime heat is affecting the color or appearance of the fruit, consider harvesting early and ripening indoors.

Blossom-End Rot

Another disorder caused by heat stress is blossom-end rot. While tied to inadequate amounts of calcium, blossom-end rot is more associated with a lack of water. The hotter the temperature, the more water is lost to transpiration from the tomato plants. This increase in water loss causes small lesions on the blossom end of the fruit that gradually spread and turn the area into a brownish or tan color. Timely irrigation and maintaining proper pH and calcium levels in the soil can prevent blossom-end rot.

White Core

Variety of beautiful heirloom tomatoes. Photo credit: USDA Lance Cheung.

Internally, tomatoes can develop a hard white core from excessive heat and inadequate fertility. In moderate cases, white core can occur just beneath the flower-shaped leaf, or calyx, on the top of the fruit. In more extreme cases, you may see white core extend through the entire fruit. Having adequate foliage cover and potassium levels can prevent white core. Additionally, older varieties are more susceptible to white core, while newer varieties are less prone to this issue. Therefore, variety selection can again help mitigate this disorder.

Fruit Cracking

Mid- to late-summer tomato harvests often occur during dry periods. However, an afternoon shower can cause the fruit to swell faster than the skin can stretch, resulting in fruit cracking. Fruit cracking can also occur through sudden irrigation during a dry spell. Cracking can be managed by reducing moisture fluctuations, and through the consistent use of drip irrigation. Mulching conserves soil moisture and reduces the risk of temperature swings. If a sudden rain shower is in the forecast after a dry spell, harvesting tomatoes at first blush or the breaker stage (a slight change in color from green to no more than 10% pink, red, orange, or yellow) and ripening indoors will keep the fruit from cracking. Research shows that ripening in a protected structure at temperatures between 55° F and 65° F is equal to ripening on the vine, while ripening at 68° F increases the sweetness and overall flavor of the tomato.

Tomatoes may love the heat, but even they have their limits. By observing your plants closely, using techniques to mitigate heat stress, choosing the right varieties, and managing soil and water strategically, you can protect your crops and enjoy a fruitful harvest. And, while the summer heat may test your patience and your plants, there’s still something magic about harvesting a perfect slicer in the middle of July—enough to make you hum a little of Guy Clark’s tune on your way back from the field.

Read more on tomato production in our ATTRA publication, Organic Tomato Production.