Tree Fruit Newsletter — April 26, 2024

April 26, 2024 Tree Fruit Newsletter

Highmoor Farm Bud Stages

McIntosh apple trees are at half-inch green as of April 25, and Honeycrisp is at green tip. Pears are at half-inch green, and peaches are at the red calyx stage.  The cold temperatures have us all worried about freeze damage, so I am resending the hardiness numbers for each bud stage.   The current cold spell will also slow down bud development and delay the date of full bloom.

Table 1. Estimated range of temperatures (°F) to cause 10% or 90% flower loss.
1/2 inch Green Tight Cluster Early Pink Pink King Bloom Full Bloom
10% 23 27 24 28 25 25
90% 15 21 28 25 28 28
For Red Delicious, measured in Washington.

 

Table 2 may be more accurate for conditions in Maine since we have not had much warm weather lately.

Table 2. Estimated range of temperatures (°F) to cause apple 50% flower loss.
Early Pink Late Pink King Bloom Full Bloom
Lower limit 21.7 22.5 23.7 24.4
Upper Limit 25.0 25.9 26.6 27.7
From Szalay et al. 2019, based on six years of research in several varieties grown in Hungary. The lethal temperature varied from year to year and among ten varieties.

Table 3. Estimated range of temperatures (°F) to cause peach 50% flower loss.
Red calyx Pink First Bloom Full Bloom
10% 27 27 27 28
90% 17 20 22 27
Colorado State Univ.

 

Renae Moran
https://extension.umaine.edu/fruit/
University of Maine Cooperative Extension
PO Box 179
Monmouth, ME 04259
(207) 933-2100
rmoran@maine.edu

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