By Alison Collin, Master Gardener volunteer
If you haven't already pruned your berry plants, it can still be done.
In its simplest form, pruning early summer-fruiting raspberries and blackberries (floricane bearers) is done by cutting out, just above ground level, all the stems that grew from the ground last year, went dormant over the winter, flowered this spring, and bore fruit this summer. These canes are usually, by now, brown and woody-looking at the base, and the foliage looks tired and old. If you follow the stems upward, they will have side branches (laterals) that bore the fruit. The new, fresher-looking canes that have grown up from the base of the plants are left, because those are the ones that will carry the crop next year. As these get taller, they are tied to supports, usually wires strung between posts. Keep the strongest growth and remove any weak stems.
Some varieties of raspberries, known as everbearing, may also produce berries on these young primocane stems in late summer and fall of the current season, in addition to the earlier crop on the floricanes. In this case, the floricanes are removed as above. After the later crop, the primocane growth is pruned by about one-third to encourage the formation of lateral branches that will carry the early crop the following year.
Primocane raspberries, which produce one crop on canes that grew from the ground in the current season, are usually left unpruned until the end of winter, when they are all cut to the ground. The fruits on these plants are produced toward the top of the new canes, so it is important to support them securely. The weight of the fruit makes the comparatively soft stems bend over, often spoiling fruit that touches the ground.
Pruning blackberries prevents the plants from becoming the unruly mess often seen in gardens, where a huge thicket of dead stems supports a few weak new ones. Especially with thorny varieties, regaining control can be a daunting task.
Blackberries come in two main types: trailing and erect. The trailing ones grow multiple stems which, as the name suggests, are not self-supporting and need to be spread out in a fan shape and tied securely to wires. Plants are often limited to about 10 stems, although in the Owens Valley I think half that number is more realistic. Erect and semi-erect types have fewer canes—some of them quite thick—and are fairly rigid, although the laterals still need support. I often get only one or two substantial canes, which I top in early summer at about 4 ft. The buds below the cut send out laterals immediately. I keep 4–6 of those and cut them back to about 2 ft at the end of winter.
The most common blackberries grown (floricane varieties) are those that fruit on canes which grew last year, went dormant over the winter, and then flowered and fruited this summer. Once the crop is finished, these canes will die and no longer serve the plant, so they should be removed as soon as possible by cutting them off just above the ground. Meanwhile, new growth will likely have sprung up from the base of the plant; these canes will overwinter, then flower and fruit early next summer, so they should be tied to the supports.
Like raspberries, there are also some blackberries that fruit twice a year, on both primocanes and floricanes. They often have the word “Prime” in their name. Pruning is similar to everbearing raspberries: the old floricanes are removed after fruiting, and the primocanes that produced the later crop are trimmed back in late winter to a point below where the fruit was produced. These will become floricanes next year and produce laterals in spring that will carry the early crop.
In both trailing and erect blackberries, the new growth develops before the harvest, so some system of keeping it safe is needed—either by bundling it and tying it to some of the wires, or by laying it on the ground along the bottom of the row. The trailing types produce multiple stems that are not self-supporting and must be spread out in a fan shape and tied securely to wires. Plants are often limited to about 10 stems, although in the Owens Valley half that number is more realistic. Prune off the tips if these stems reach 8–10 ft.
Erect and semi-erect blackberries have fewer canes—some of them quite thick—and are fairly rigid, though the laterals still need support. I often get only one or two substantial main stems. These I top in early summer at about 4 ft. The buds below the cut send out laterals, and I keep 4–6 of those, spreading them out on either side of the plant. I then cut those back to about 2 ft at the end of winter.
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Photo by Jametlene Reskp on Unsplash.