Apples: Reflections on spring frost during bloom in 2026

 Article written by Madeline Wimmer, UMN Extension Fruit Production Educator, based on discussions by David Bedford, UMN fruit breeder and researcher. 

Each year, the Minnesota Apple Growers Association hosts a summer tour at a commercial apple orchard location in Minnesota for growers to come together and learn during the growing season. This year, the summer tour gathered in early August at Fall Harvest Orchard. The University of Minnesota’s apple research, breeding, and education team hosted part of the program within the orchard to discuss a number of topics including dogwood borer, red star rust, and season trends. 

Image: David Bedford discusses the topic of spring frost in 2026 at this year’s summer tour.  

David Bedford, UMN researcher and plant breeder, talked about spring frost during bloom. While Minnesota has historically escaped much damage from spring frost episodes due to delayed bloom times compared to other Midwest regions, the UMN Horticultural Research Center (HRC), located near Chaska, Minnesota, experienced nearly 80% blossom damage this year due to two separate freezing events. 

The UMN HRC also observed less-than-usual symptoms. Often damaged blossoms will show petal browning; but this year, there was no petal browning. Instead, the damage was localized to the reproductive parts. 

Image: Two blossoms showing freeze damage (top) above two others that are healthy (bottom). Photo taken by Josie Dillon, University of Wisconsin Extension Fruit Outreach Specialist. 

Factors leading to spring frost damage

David mentioned that three factors primarily impact how severely freezing episodes impact blossoms: 1) temperature and duration, 2) growth stage and bloom time, 3) topography and planting locations. 

Apple blossoms are vulnerable to damage around 28F, which is the most tender time for the trees. This can lead to around 10% damage of blossoms; however, if temperatures decrease further, even just by a few degrees, there can be up to 90% blossom mortality. 

Because varieties bloom at different times, this also changes how a spring frost will impact blossom mortality. Additionally, not all apple flowers bloom at the same time, with the first flowers unfolding being the king blossoms. 

In the case of the HRC’s damage this year, the earlier blooming varieties actually escaped the frost because of the timing of the frost events. It was the mid-blooming varieties that bore the most damage. While some growers may think one of their varieties has hardier blossoms, there isn’t evidence that this is the case beyond the actual bloom time.

Finally, orchard topography and where apple trees are planted can make a big difference. Cold air sinks, and low spots can be at greater risk for frost and cold damage. David pointed this out in a section of the orchard where SweeTango was planted in a row that went from the top to the bottom of a slope, and trees at the bottom of the slope had more damage. 

Sometimes this can even mean that lower sections of the canopy will receive more damage. This happened with taller pear trees at Fall Harvest Orchard where the majority of the fruit set was on the upper portions of the canopy. 

Image: David Bedford discusses pear production at Fall Harvest Orchard, noting increased fruit set within the higher regions of the tree canopies likely due to spring frost. 

Preventing spring frost damage 

What can be done to prevent frost damage in orchards? Many options end up being costly and not practical for most orchards, or applicable to the types of frost the majority of sites experience. 

For example, orchard fans can help mix air when radiative frosts happen, which cause thermal inversions in the orchard, but will not help in the case of a convective frost where the air is already mixed. For most Minnesota orchard sites, thermal inversions are less common than other regions of the U.S.  

Overhead irrigation works by creating a continuous layer of water that releases heat when it turns into ice, but it must be strategically configured, takes a lot of water, and needs to be run until temperatures rise above freezing, or it can lead to damage. Other mitigation methods may include smudge pots, which are resource intensive. 

Site layout is one method that can help prevent frost damage from planting onward. It might be tempting to fill in orchard low sites with a few trees to make up for bare land, but it should be considered that crop loss will likely happen eventually during years with spring frost conditions during bloom. David mentioned that even 20 feet of drop within an orchard can make a difference.  

Ensuring adequate fruit set

Even if your apple crop escaped a spring frost event, adequate fruit set still depends on other factors like pollinator activity, which can also decrease when temperatures and the weather is suboptimal. Especially noted are honeybees, which prefer to fly when it is warm, dry, and not too windy. 

Finally, cold weather can impact how well the pollen tube grows down to fertilize the apple ovaries. With all these factors and so many chances for something to go awry, it’s a good thing most apple trees produce more blossoms and fruitlets than needed by the time fruits are ripe and ready for harvest (only 15% of blossom fertilization is typically needed for a good harvest). 

And hopefully the variety isn't prone to dropping fruit prematurely as an added trait to manage at the end of the season. In this way, apple crop load can feel particularly interesting to manage. Switching from hopes of a high fruit set during bloom, to wishing for successful thinning post fruit set, watching more fruit drop during June drop, and hoping the remaining fruit doesn’t drop prematurely as harvest approaches.  

Thank you to our farm and ag professional partners for contributions to the UMN Fruit Update series. Non-credited photos in this article were either taken by Madeline Wimmer or within the UMN Extension system.