Another year, another round of blackberry flower bud injury

Blackberry flower bud damage. The centers are the female part of the flower (a gynoecium with many pistals) develop into the fruit. Image above shows 3 out of 5 flowers with blackened centers, indicating that there was lethal damage and fruit will not develop.

Since 2007, just as the NC blackberry industry began to emerge, spring time cold temperatures have killed flowers multiple times (my blog says 2007, 2012, 2014, and 2018, but there may be more). 

Last week, just as we began to think we had missed any chance of bud injury, temperatures dipped to 27F or below.  Blackberry shoots with developing flowers were emerging. There was a wide range of damage, depending on location, degree of bud break, and temperature. Locations and cultivars on the same farm had  in some cases little or no damage to 40% damage to the primary flower buds. 

Growers know what to look for (blackened centers) and had been assessing their crop for the last few days. See image above. In most cases the king or largest flower bud was damaged and some of the secondary and tertiary flower buds also were damaged. The smaller flower buds with green centers will develop into fruit. 

When we see this type of damage, often there are secondary shoots that will emerge and produce flowers a week or so after the initial damage. Look for succulent lighter green often elongated shoots. (Sorry no image, if you have one, send it to me and Ill post it here). The extent of secondary shoot emergence is not consistent. It likely depends on extent of damage to the primary flower buds, cultivar, how well the secondary shoots had developed in the previous year.  We have done some shoot removal studies in the past. These will be summarized in an upcoming post.

Meanwhile here is a link to posts from the past on this topic.
https://teamrubus.blogspot.com/search?q=freeze+