I’m not sure. The best stone fruit coming out of commercial production from CA is usually earlier in the season- now that most of the best acreage is used for wine grapes, and I’ve always thought that later fruit tended to be mushy because it was partially cooked on the trees- at least with peaches and nects. I have noticed that the high humidity in a greenhouse makes a big difference an the ability of plants to photosynthesize. But never mind me- what does CHAT have to say about it.
1. Heat Stress and “On-Tree Cooking”
- When daytime highs regularly exceed ~95–100 °F (35–38 °C), fruit surface temperatures can climb much higher than air temperature, especially in direct sun. This can lead to:
- Flesh breakdown (a kind of partial cooking or “gel breakdown”).
- Loss of acidity, giving fruit a flat taste.
- Inhibited sugar accumulation, since respiration burns more sugars at night when it stays warm.
- UC Davis and Clemson trials both note that in very hot valleys (like California’s San Joaquin in midsummer), peach and nectarine color and firmness hold, but flavor often suffers—growers mitigate with shading, irrigation, and selective harvest timing.
2. Goldilocks Zones
- The highest-quality peaches and nectarines consistently come from areas with:
- Warm but not extreme days (mid-80s to low 90s °F / 29–33 °C).
- Cooler nights (below 65 °F / 18 °C), which reduce fruit respiration and let sugars accumulate.
- This is exactly the “Mediterranean” band you describe—regions like:
- Central Italy and southern France (Provence, Languedoc).
- Northern California’s coastal valleys (Sonoma, Santa Clara historically).
- Some parts of Chile’s Central Valley.
- These climates strike the balance between adequate heat for sugar development and cool nights to preserve acids and aromatics.
