University of Maryland Extension

Cultivation Range

Since aronia has a chill requirement for break winter dormancy, not all locations in the U.S. are suitable for fruit production. Breaking winter dormancy requires that dormant buds receive a minimum of chill time before they can open in the spring. Since all the varieties are of similar genetic stock, they have very little if any differences in their chill requirements. Chill zones are not related to climate zone maps.

Chill hours are calculated several ways, depending on the model used. The single chill hour model calculates the accumulated time that temperatures are below 45 degree F. For every hour below 45 degrees, a chill hour is accumulated. Similarly, a dual temp model calculates time between freezing and 45 degrees F. Another model assigns weighted temperatures, giving a full chill unit between 36 and 48 degrees F, a half unit to temperatures between 34 and 36, and 48 and 54 degrees F. Temperatures lowers than 36 degrees F and between 54 and 60 receive no chill units. Interestingly, temperatures between 60 and 65 subtract a half unit while temperatures above 65 subtracts a full chill unit, actually reversing the chill accumulation. 

Several years of dormancy studies at the University of Maryland have revealed preliminary estimations on the southern range of all aronia varieties which is around 1000 chill hours (using the dual temperature model). The map below shows the average yearly accumulation hours in the contiguous for the dual temperature model. The blue represents the northern most average range of 1000 chill hours. A blue circle on the border of Georgia and Tennessee is an expanded area below the line due to the high elevations. The large blue circle in North Dakota indicates that this region does not accumulate over 1000 hours of temperatures between freezing and 45 degrees. Temperatures of obviously much lower. There seems to be no problem with growing aronia in that region.

This is an estimation only. Yearly changes in temperatures can affect what regions consistently get the appropriate chill hours. Some years along that blue line may not receive the needed chill hours. If you are newar these bliue lines, testing a few plants in your location for several years may be necessary.

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