Winegrowers are nothing if not adaptable, given that the grape is a harbinger crop, or in more prosaic terms, the canary in the coal mine for agriculture. As a result, when climate shifts generate more frequent heat waves of higher temperatures and longer duration, viticulturists swing into action with a toolbox of methods to mitigate the effects. 

Growers use misters to cool the air around the grapes, irrigate in advance of heat waves to prevent dehydration, and even apply anti-transpirants that work like sunscreen to protect from sun damage. Medium-term options include changing canopy management to delay ripening and using regenerative farming techniques to boost water retention in the soil. 

The most aggressive strategies involve relocating vineyards to cooler microclimates or pulling up and replacing less heat-tolerant varietals. However, vineyard owners are unlikely to invest in these approaches while consumption and demand are declining. 

A better alternative would be to focus on erecting permanent shade canopies to protect their more heat and sun-sensitive grapes. 

Studying the impact of shade canopies

In preparation for a study on mitigating heat and solar radiation in vineyards, Lauren Marigliano, PhD, now Assistant Viticulturist at Napa’s Silverado Farming Company, constructed overhead shade structures using solid polyethylene plastics. Her goal was to determine the impact of using these shades “as a dimmer switch so that growers can select the parts of the sun they want to block.” She examined whether the shade impacted photosynthesis, ripening capacity, and or the resulting wines’ flavor profile and color.

During a pre-veraison heatwave in 2020, the area under the shade structure remained warmer overnight and was cooler at the end of the day than in the control environment. In contrast, the control reached 122°F, much higher than the 95°F that Marigliano describes as ‘the danger zone,’ after which the risk of sunburn, dehydration, anthocyanin degradation, and halting ripening sets in. Evapotranspiration tracking also revealed that the shade canopies reduced water loss by 30%. 

Perhaps Marigliano's study's most striking result was the wine tasting by a hundred wine professionals. Their finding: the taste and smell of wines made from shaded grapes were distinctly different from the control and consistently preferred. 

Overhead shade structures are clearly effective in reducing the impact of extreme heat on vineyards. The findings should give growers the confidence to install them in an existing vineyard to provide much-needed cooling on hot days rather than pulling out the vines.

Marigliano recommends “Overhead rather than side netting as a long-term solution, especially something you want to maintain throughout the growing season or all year. It is easier to use because you can get underneath it and do all your canopy management and spraying without having to put up and take downside netting every time you want access.” 

Flexible concrete support for overhead shade structures

“Harvest Pillar can come in a few different sizes with lengths up to 24 ft,” says Robert Alamo, an outside sales representative for Harvest Pillar by Jensen Precast. “The stronger, longer-lasting concrete can be used for trellising, overhead shade projects fencing, or anything else you would use a wood or steel post for.” 

“These posts can really hold up to the high-load capacities needed in shade canopy systems,” adds George Kehagias, Director of Product Management for Harvest Pillar. “Even if they're running machinery, which is probably 12 to 15 feet in height, under the canopy, they can get posts 15 to 17 feet out of the ground, with about one-third of the height underground to provide stability.”

Although steel and wood can deliver these heights, they don’t provide the same solid structure that concrete does. In extreme wind, wood can snap, and steel can bend while concrete stays put. Concrete also lasts much longer than wood or steel since it doesn’t rust or attract pests and diseases. Harvest Pillar is exceptionally durable because they are made of prestressed, high-quality concrete that can withstand all types of weather conditions and even fire. The flexibility comes from encasing steel tendons into the concrete mixture.

Kehagias explains, “We take stranded cable and tension it and then pour concrete over it, allow the concrete to harden, and then you cut that cable. The tension compresses the concrete and creates that flexibility.”

“Prestressed concrete has been around since the late ‘50s,” notes Alamo. “It's been used in vineyards in Europe since the early 1970s, and more importantly, it's still their post of choice today. Harvest Pillar has been shipping from coast to coast since the spring of 2024. And because our European friends have been using concrete posts for so long, they have all the accessories figured out. Gripple, one of the industry's leading vineyard suppliers, has a whole line made specifically for our concrete posts, so there's a solution to every challenge.”

For more information on how Harvest Pillar can help you combat high summer temperatures, contact the Harvest Pillar team by visiting our website, HarvestPillar.com, or calling (559) 315-4522.