Q. In April, I planted new black raspberries (munger variety). They have grown to 8ft with only 2 vines per hill. Should I cut them back to 5ft (like I did the old red plants) or can I trellis them like loganberries. I’m looking for maximum yield. Gary Pedersen – Tacoma, WA
A. Munger is a popular variety in the PNW both with home growers and commercial growers. Commercial growers favor them because they are robust and good for mechanical harvest. There are many different ways to prune and train different brambles (blackberries, raspberries, black raspberries and their various crosses). Much of this has to do with the habit of the particular type you are working with. Brambles can be upright, semi-upright, or trailing in habit. The most typical pruning scenario for the Black Raspberries (Rubus occidentalis), which has an upright habit, is to pinch the first year canes (primocanes) back at 2 feet tall to force out lateral branching. This keeps the fruit production in a more compact space. Then in the winter the laterals that formed are cut back to a foot or so forming an oval shaped hedge. I believe this method was translated from the commercial growers back to the home growers. You have missed the window to prune them this way. Any pruning done during the winter reduces the number of flower buds that will be produced in the second year when the primocanes (first season growth) become floricanes (second year flowering/fruiting). Once the canes fruit they are mortocanes – no just kidding – I made that one up. But you get the idea. The canes die after the second year and should be pruned out. So if you want to get maximum production this year just give the canes some support and then start a new pruning regime the new primocanes. The loganberry you mention has a trailing habit and therefore can be trained in a variety of ways on trellises. My favorite way for my Marionberries (trailing habit) is a looping system on wires. This allows the use of the full length of the canes and maximizes fruit production.
For more info on the various ways of training brambles see the WSU online publication: http://cru.cahe.wsu.edu/CEPublications/eb1640/eb1640.html