1922 to Present at the WSU Tree Fruit Research & Extension Center Wenatchee, WA
Updated by Tianna DuPont, WSU Extension March 11, 2019; from Tim Smith WSU Extension emeritus.
The date of full bloom at the WSU Tree Fruit Research and Extension Center is used as a relative comparison of one year to another. The 93 year average date of Red Delicious apple full bloom at WSU TFREC is May 4. The earliest Full Bloom date of all time at this site of April 9 was recorded in 2015 and tied for earliest again in 2016. The bloom date for 2017 was May 1. The bloom date for 2018 was April 28.
As of March 10, 2019 the model predicts full dormancy with 210 DD less than normal.
Daily high temperatures are used to predict bloom based on degree days (DD) above 43℉. Daily DD are equal to daily high – 43℉.
920 DD predict first bloom. 250 predicts late dormancy, 331 silver tip, 440 green tip. As always look at the trees. Models are never perfect.
For more accurate predictions for multiple varieties take a look at the new Decision Aid System model for bloom at https://decisionaid.systems/
Red Delicious Apple Historical Full Bloom recorded in Wenatchee, WA
|Bloom by Year||Earliest to Latest|
The data in the table was provided from 1922 to 1993 by the various people who worked for the National Weather Service office in Wenatchee, for the fruit growers and public. Since the NWS office was closed in 1993, the date of full bloom has been monitored at the WSU Tree Fruit Research and Extension Center by the Regional Extension Specialist from the Chelan / Douglas County office of WSU Extension. These data are of both significant historical and practical importance, and are used by various individuals to better understand production, harvest and quality of the past crops produced in the region.
Full bloom is defined as the day that 60% of “king blossoms” are open on the north (shady) side of the tree. (The king blossom is the larger dominant blossom that is usually found in the center of the blossom cluster, surrounded by the yet unopened “side blossoms.”) Frosted blossom buds may open with an incomplete or missing king flower.
Red Delicious is a relatively late blossoming apple cultivar, and other apple cultivars on warmer sites in the local region will bloom up to a week earlier. Elevation and slope aspect are quite variable over short distances in this region, and very influential in relation to blossom development rate. Lower elevation orchards (~700 ft. elevation) may see blossoms up to a month before higher elevations (~3,400 ft.) in this region. Apricots bloom first in the region, usually three weeks before Red Delicious growing on similar sites. Then peaches and nectarines bloom, about 14 – 17 before apples, then cherries about 10 – 14 days before apples, then pears about 7 – 10 days prior, then come the apples.
Some Fun Facts:
As of 1925 through 2018, the 93 year average full bloom date in Wenatchee is: May 4.
The Average Full Bloom Date From 1995-2005 is: April 23
The Average Full Bloom Date From 1990-1999 is: April 21
1980-89: April 25
1970-79: April 30
1960-69: April 28
1950-59: May 2
1940-49: April 26
1930-39: April 26
WSU Extension Specialist, Tree Fruit