A Chilling Tale of Three Blueberry Cultivars

The number of chill hours we received this year has been lower than usual (see Chill Hour link on right side of this page). I am in the process of accumulating chill hour data from the last 15 years or so to see how (or if) it has changed over that time period. At any rate, this year was somewhere between 500 and 600 hours here in Poplarville.  Enough for most blueberry cultivars, but not all. To this point, see the photo below.

From left to right: Springhigh, Jewel, and O'Neal southern highbush blueberries. Notice that O'Neal has no leaves compared to the other two.

From left to right: Springhigh, Jewel, and O’Neal southern highbush blueberries. Notice that O’Neal has no leaves compared to the other two.

Springhigh has a low chilling requirement of 200 hours. It is also very early blooming which causes problems in our location most years. This cultivar was released in 2005 out of Florida.  Jewel has a similar chilling requirement of about 250 hours. It too is from Florida. O’Neal is much different from the other two.  For flowering it requires about 400-500 hours of chilling; however the leaves have a higher requirement. Although I would not consider the flowering good on this bush it has some. Leaf development is known to be slow and sporadic on O’Neal anyway in the spring. This cultivar is from North Carolina.

I suspect that the amount of chilling we received fell in the area of enough for O’Neal flowers but not quite enough for O’Neal leaves. Leaves will continue to emerge but may take longer than normal. That delay in full leafing may affect the quantity and quality of the crop on O’Neal, whereas both look fine on Springhigh and Jewel.

This publication from Georgia has good information on these cultivars and chill hours.