The following information may be of interest to Alaskan raspberry growers. It is from the World Wide Web at:
Research by Dr. J. P. Prive of the Michaud experimental Farm in New Brunswick, Canada, has shown that light interception is critical to maximizing yields, and that the best way to increase light interception is to reduce cane density.
Although the normal practice is to thin out excess primocanes (next year’s fruiting canes) in the fall, thing is better done in the summer, when primocanes are about a foot tall. This way, the superfluous primocanes won’t shade out the current year’s floricanes, and the resulting yields are higher. In Prive’s test, summer thinning of primocanes resulted in a 23% greater yield over fall thinning. The optimum density (in New Brunswick) is 16 to 20 canes per meter (4 to 6 canes per foot) of row. Spent floricanes should not be pruned out until late in the fall, because even after they finish cropping, they continue to photosynthesize and build up root reserves.