Assessing Cold Injuries to Blackberry Flower Buds

Blackberry growers may get a false sense of relief when they do not see any damage to the leaves or the exterior of the flower buds. The record snow and low temperatures we experienced during the week of April 19 to April 23 may have caused damage to flowers without growers’ knowledge. The leaves on the blackberry bushes may look okay. However, growers may want to sample the flowers by cutting at least ten flower buds open to see what is inside. If the center is black, the pistil or the female part of the flower buds is dead. No fruit will form from the flower buds with the dead pistil. If the center looks great, then everything is good!

Flower bud on a fruit lateral of a blackberry shoot. Photo by Ryan Slaughter, Research Assistant, CFAES South Centers.Ryan Slaughter, a research assistant for the small fruit program at CFAES South Centers, sent me a few pictures on April 23. One of them is a close-up of the blackberry fruiting lateral with new leaves and a flower bud on the tip.

Flower bud on a fruit lateral of a blackberry shoot. Photo by Ryan Slaughter, Research Assistant, CFAES South Centers.
The flower bud may look okay from the outside. However, a true test is whether the pistil is still alive. The only way to know for sure is to cut some of it open to see what is inside. If everything is nice and green, then the flower is still alive. If the center or the pistil is brown or black, then the pistil is dead. Growers may want to sample 10 or 20 to get a percentage of bud kill. They will then know how much of a yield loss this freeze event has caused.  

lackberry production in a high tunnel at CFAES South Centers. Photo by Gary Gao, The Ohio State University.In Ohio, blackberry production is always a highly challenging endeavor since blackberry bushes are not very hardy. Low temperatures can kill Floricanes and flower buds. This is why I only recommend two ways for growers to grow blackberries. They are rotatable cross trellis and high tunnels. The third way is to grow primocane blackberries. However, this method is only recommended for southern Ohio.

Injuries to blackberry by cold temperatures seem to get more and more common. Winter protection for blackberry plants seems to be more of a necessity than a luxury. Perspective growers are encouraged to reach out to Dr. Gary Gao at for more information.

Blackberry bushes on rotatable cross arm trellis with row cover for winter protection. Photo by Gary Gao, The Ohio State University.Based on the 2017 USDA Ag. Census, there were 310 acres of blackberry plantings in Ohio. There has been a rapid growth of blackberry acreage. Most of these blackberry bushes are on the rotatable cross-arm trellis. The system can be expensive. It takes $22,000 to get one acre of blackberry established. But, the gross revenue can be $45,000 per year for many years. It is a typical case of high input and very high return!

I hope this article is of benefit to you. We are here to conduct research and extension for you, the fruit growers, and taxpayers. Our projects have been supported by various grants from the Ohio Department of Agriculture, USDA, and OVSFRDP. We thank them for their financial support!

Follow this link for more information on various fruit crops at CFAES South Centers:

Gary Gao, Ph.D.
Professor and Extension Specialist 
CFAES South Centers, Department of Extension