According to the Blackberry chilling model CRONOS, at the Piedmont Research Station in Salisbury, we have accumulated 794 hours. Thornless blackberries need 700-1100 hours, and raspberries need 800-1700 hours. So for blackberries, we have experienced enough cold for some of them to break bud. BUT I don't think we are anywhere close to that based on field visits last week.
|Pruning Navaho thornless blackberries at Mitchem Farm in Vale, NC.|
FYI I discussed chilling in a series of previous posts:
Here is an excerpt from one of those posts
High chilling/low chilling. Most of the blackberries and raspberries we grow in NC need to accumulate a high number of chilling hours in order to break bud and grow 'normally' next summer. Contrary to what you may initially think, we don't want low chilling plants. We want high chilling plants that can stay dormant when we get January thaws.
If you live in the SEUS, you can find probably find out the chilling hours in your area. The NC State Climate office has a great tool you can use if you want to calculate the chilling hours in your area. Here is a link. http://www.nc-climate.ncsu.edu/cronos/blackberry/