Hello, Christopher.

It’s great that you are embracing the stewardship of the Honeycrisp trees! 

Honeycrisp apples are one of the varieties susceptible to bitter pit. This article about bitter pit and possible causes offers some other factors to consider regarding the calcium uptake, including soil pH, uneven watering, possible over-fertilizing, and “excessive tree vigor.” The University of Wisconsin’s Plant Disease Diagnostics Clinic lists moisture stress as a factor in bitter pit and suggests providing consistent irrigation to the trees. Given the inconsistent precipitation Minnesota has experienced in the past few years, that might be a good place to start.

If you have not already submitted a soil sample to the University of Minnesota’s Soil Testing Lab, I would suggest that as a first step. All the articles I read indicated the problem can be caused by over-fertilizing, so it would be good to know what your soil is holds. Once you know your soil’s contents and levels, you could amend the soil as necessary. The author of the article indicates that calcium sprays should be used only after all the other factors have been considered.

This Michigan State University article provides some tips to increase calcium, should you go that route.

For other general apple tree questions, I usually start at the University of Minnesota’s Growing Apples in the Home Garden page.

I hope this helps guide your decision and results in less pitted fruit.

Sincerely,

Julie 

Sources:

https://ucanr.edu/program/uc-anr-small-farms-network/maximizing-calcium-uptake-apples

https://hort.extension.wisc.edu/articles/bitter-pit-and-cork-spot/

https://www.canr.msu.edu/news/bitterpit_control_in_apples

https://soiltest.cfans.umn.edu/testing-services/lawn-garden

https://extension.umn.edu/fruit/growing-apples