That juicy, sweet peach you savor in the peak of summer is actually a product of winter’s chill, quietly working behind the scenes to ensure a bountiful harvest. While it may seem counterintuitive, our orchards rely on the chill of the colder months to produce the bountiful harvests we cherish each year. This essential process revolves around something called chill hours, and as our climate changes, understanding the importance of chill hours becomes even more critical.

What Are Chill Hours?

Chill hours are the cumulative number of hours when temperatures range between 32 and 45 degrees Fahrenheit¹. These hours are vital for our stone fruit trees—peaches, nectarines, apricots, plums, pluots, and cherries—triggering dormancy, a crucial resting phase that prepares them for the growing season.

During dormancy, trees conserve energy and build reserves needed for producing vibrant blossoms and abundant fruit in the spring. This period also helps synchronize bloom cycles, ensuring that pollination happens efficiently². Without sufficient chill hours, trees may struggle to emerge from dormancy properly, affecting their ability to produce healthy blossoms and, ultimately, delicious fruit. 

But so far so good in 2025! As of February 16th, we are up to 819 chill hours in Brentwood, which is some of the best we’ve seen at this time in the past five years. This is great news for our orchards, and with these favorable conditions, we’re predicting a strong harvest this spring!

The Decline of Chill Hours and Its Impact

Farmer Al has observed a decline in chill hours over the past decade, and this trend poses significant challenges for our orchards. While this year’s numbers are promising, the long-term trend remains concerning. When trees don’t receive enough chill, they struggle to wake up properly in the spring. Consequences of an inadequate amount of chill hours include:

• Insufficient chill causes trees to leaf out late, prolongs the blooming period, and weakens buds, which may deteriorate or drop, leading to fewer flowers. Since fruit forms from flowers, this directly results in smaller harvests¹.

• Inconsistent chill disrupts fruit size, shape, and overall quality while also affecting ripening patterns. This lack of uniformity makes harvesting more challenging for our farm crews.

Chill hours are a natural requirement that ensures our orchards remain productive and resilient. However, as climate patterns shift and chill hours become less predictable, we must be proactive in understanding their impact and finding innovative ways to adapt.

How We’re Adapting

At Frog Hollow Farm, we refuse to be complacent, which is why we are taking proactive steps to mitigate the challenges posed by declining chill hours. One key approach is diversifying our crops. We’re planting more trees that require fewer chill hours, such as mulberries, and incorporating new varieties of stone fruit that can thrive with less dormancy. For example, Bing cherries require a minimum of 800 chill hours to set a crop, whereas the newer Royal Tioga cherries need only 500. As our Bing cherry trees age, we are gradually replacing them with Tioga cherries to better align with shifting climate patterns.

In addition to crop diversification, we continue to embrace regenerative farming practices. Our methods focus on improving soil health, increasing biodiversity, and reducing our overall carbon footprint to help combat climate change. While we can’t control the weather, we can control how we respond to it, ensuring that our farm remains resilient and productive for generations to come. 

By staying innovative and adaptable, we will continue to grow the high-quality fruit our customers love, despite the challenges posed by a changing climate.

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[1] University of California, Agriculture and Natural Resources. https://ccmg.ucanr.edu/files/77176.pdf

[2] Frontiers in Plant Science. https://pmc.ncbi.nlm.nih.gov/articles/PMC6759871/