Blog 12-12-25
Peaches: Mid December Cold Hardiness Update
Updated forecasts for this coming Monday are predicting low temperatures around 0 °F. A closer look at the daily highs and lows from the last two weeks (Figure 1) shows a drop in temperature this past Tuesay, December 9th, 2025. Cold hardiness is very dynamic throughout the season and will vary by cultivar and location of the orchard site. Low temperatures like the drop on Tuesday will signal to a tree to acclimate to withstand continuously lowering temperatures.
Looking at the hardiness data from samples of ‘Contender’, ‘July Prince’, ‘Jersey Queen’, and ‘Loring’ collected yesterday, December 11th, we can see that acclimation to these temperatures are happening in real time.
Samples were tested for cold hardiness by collecting one year old peach branches and removing the floral buds. The buds are subjected to various cool temperatures ranging from 32 °F to -4 °F, simulating the drop in temperature during an evening. After the buds thaw to room temperature, damage is evaluated by cutting open each bud. A binomial regression model is fit to the data and the LT10 , LT50 , and LT90 are calculated and plotted onto a graph.
Because of Tuesday's low temperatures, it was observed the LT50 of both 'Contender' and 'July Prince' (Figures 2, 3, 4, & 5) are right around 1 °F, the projected low temperature for this weekend. This is lower than was observed last week on December 2nd, 2025 and December 4th, 2025.
Each peach variety will differ from each other in hardiness. This can be seen by observing 'Loring' and 'Jersey Queen' (Figures 6 & 7) which are less hardy than 'Contender' and 'July Prince'.
|
Variety |
Date Collected |
LT10 (°F) |
LT50 (°F) |
LT90 (°F) |
|
Contender |
12/02/2025 |
10.6 |
5.2 |
-0.1 |
|
Contender |
12/11/2025 |
8.8 |
0.7 |
-7.4 |
|
July Prince |
12/04/2025 |
12.5 |
4.9 |
-2.7 |
|
July Prince |
12/11/2025 |
7.8 |
1.4 |
-5.0 |
|
Jersey Queen |
12/11/2025 |
26.3 |
12.1 |
-2.2 |
|
Loring |
12/11/2025 |
13.4 |
4.9 |
-3.2 |
Table 1: Lethal temperatures (°F) for 10% (LT10), 50% (LT50), and 90% (LT90) floral bud kill in peaches. Observations in red are the most recent updates to peach cold hardiness from December 11th, 2025.
If the forecasted temperatures are reached, expect to see 50% floral bud mortality for ‘Contender’ and ‘July Prince’. Expect to see 50% floral bud mortality at 12 °F and 90% floral bud mortality at –2 °F for ‘Jersey Queen’ as well as 50% floral bud mortality at 5 °F and 90% floral bud mortality at –3 °F for ‘Loring’.
For commercial growers with questions or concerns, please reach out to Elayna Stirn, Brent Arnoldussen, or contact us through our social medias.
12/10/2025
Authors: Elayna Stirn, Brent Arnoldussen