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As the summer season arrives across California’s avocado groves, it’s the perfect time to revisit best practices for tree health and fruit quality. In June and July, our team at Index Fresh hosted regional Gather & Grow in-field meetings to discuss pressing seasonal topics with growers. For those who couldn’t attend, we’re sharing the highlights and actionable tips below so your orchard can thrive through the critical months of July to September.

Understanding Phenology: Setting the Stage

Avocado trees are finishing the demanding flowering and fruit set phases. These have required significant tree energy. Now, exponential fruit growth begins, coinciding with key periods for shoot and root development. Your summer decisions will have a lasting impact on fruit size, yield, and tree vigor throughout the season.

Summer Cultural Practices for Success

Fertilizer Plan

Irrigation Management

Pruning Practices

Goals:  Improve light penetration, make harvesting safer and easier, streamline spray coverage, and ultimately maximize yield and fruit quality.

How-To:

• Remove dead wood for canopy health.
• Maintain a healthy balance between fruit- and leaf-producing shoots.
• Protect newly exposed branches from sunburn with a water-thinned white paint.
• Disinfect pruning tools between each tree to prevent disease transmission.

Mulching for Roots and Soil Health

Mulch renewal is timely now. A fresh layer:

Heat Management Strategies

• With peak summer heat possible, water is your first line of defense.
• Apply up to 50% more than your typical irrigation volume the day before an anticipated heatwave.
• Use shorter, more frequent irrigations during heat events to reduce crop stress and prevent fruit drop.

We encourage you to review these practices with your Field Representative and adapt them to your unique conditions. As always, Index Fresh remains available for consultation or in-grove advice—reach out if you would like personalized recommendations.

Here’s to a safe and productive summer!

By Gerardo Aldunate, Agronomist, Index Fresh

Overhead sprinkler systems are proving to be a powerful tool for protecting avocado orchards from extreme heat. Research has shown that using these systems can drop the air temperature around avocado trees by 7–12°F, providing a critical buffer against heat waves that can cause stressed trees to shut down and crops to suffer severe damage (Miller et al., 1963; Lomas and Mandel, 1973). More recently, a 2022 study published in Nature documented how Israeli researchers saw up to a 100% increase in avocado yields when using canopy-cooling systems during heat spikes. In trials across three Israeli orchards—where temperatures soared to 113°F—overhead irrigation reduced air temperature by 18–21°F and boosted relative humidity by 16–18%. While the concept isn’t new or particularly high tech, the adoption of overhead sprinklers in avocado farming is on the rise as growers seek practical strategies to mitigate the growing challenge of extreme heat.

Evapotranspiration is the key process at work. As plants transpire, they release water vapor through their leaves, cooling the surrounding air—a natural effect similar to condensation on a cold glass. Overhead sprinklers amplify this cooling by adding moisture directly to the orchard environment, resulting in even greater temperature reductions and increased relative humidity.

At Brokaw Ranch Company in Santa Paula, nearly 50 acres are equipped with overhead sprinklers—an investment in preparation for the inevitable 100-degree days of August and September. Ranch Manager Nathan Lurie reports that the system is effective, and the ranch now considers overhead sprinklers standard practice with all new plantings.

Hot temps trigger avocado trees to close their pores

When temperatures rise above 88°F, avocado trees will start to enter the danger zone. Their stomates—leaf pores crucial for gas exchange—close to conserve water under intense heat and low humidity. This defense mechanism, however, restricts both water uptake and respiration, stunting photosynthesis. If these high temperatures persist, trees can experience fruit drop, reduced yields and size, and, in extreme cases, fatal stress. Because avocados are tropical trees with shallow root systems, they are especially sensitive to heat events, which are becoming increasingly common in California’s avocado regions.

According to Lurie, advances in weather forecasting allow growers to anticipate and prepare for heat waves with precision. One of the best preventive measures is to increase ground irrigation in the days ahead of a forecasted heat spike. During a heat event, orchards equipped with overhead sprinklers, like Brokaw’s, activate the system hours before temperatures reach their peak. Water supply and pressure limitations mean not all orchard sections can be irrigated simultaneously, so the sprinklers are cycled in advance to rotate through each section.

The overhead sprinklers complement increased ground irrigation. By cooling the canopy, the sprinklers help keep the stomates open, allowing trees to continue metabolizing and making use of the extra irrigation, instead of shutting down under heat stress.

Overhead sprinklers are especially vital for newly planted trees in heat-prone areas, giving them a greater chance to survive their critical establishment years. For mature trees, the system helps prevent crop losses and canopy/limb damage from severe sun burn.

“Overhead sprinklers help prevent loss from heat damage to the current crop and often next year’s crop. In extreme heat, you could be looking at limb damage and reduction of crop even two to three years out,” notes Lurie.

While growers in other crops have used overhead sprinklers for decades to mitigate heat and frost, avocado growers are only now widely adopting this technology. Much of the foundational research comes from Israel, where heat challenges mirror those California now faces—especially in the southern regions and inland Ventura County.

For growers considering this enhancement, Index Fresh Field Representatives can assist in evaluating and implementing overhead sprinkler systems, offering guidance where the return on investment may be substantial—particularly if the alternative could mean significant crop or tree loss.