Wednesday, November 2, 2011

Freeze ends blackberry harvest

We have a trial of primocane-fruiting blackberry selections at the Upper Mountain Research Station in Laurel Springs, NC. One set of plants are grown outside and another set are under a multibay high tunnel. Normally Laurel Springs gets its first frost in the first week of October, however this year, it did not occur until last week. 

On October 17, Absalom, my assistant,  took a picture of a developing fruit cluster (photo on left). The fruit was green and there were a couple of flower buds.  He took a photo again of the same plant and same flower cluster  on October 24 (photo on right). The night before, temperatures had dropped to 22 F in the open field and almost as cold in the tunnels. All the green fruit had turned brown and the flowers had turned black in the centers.

We are conducting a few tests, but our initial thoughts are that both the chlorophyll and phenologics ozidized as a result of exposure to freezing temperatures. This is what happens to grape berries in the fall that are hit by cold before they are harvested.

The tunnels did provide some protection, but not enough to save the crop. We estimate that we lost 70-80 of our potential yield. We will be reporting on this more this winter at grower meetings. 

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