How to Prune Brambles
By: Lee Reich
Of the many types of backyard brambles (Rubus), blackberries and raspberries are some of the tastiest and easiest fruits you can grow-but only if you prune the plants diligently and regularly. Pruning a bramble patch is not difficult, and nothing like the intricate combination of art and science needed to prune apple trees. Depending on the kind of bramble, it's just a simple three- or four-step procedure.
Why Prune Brambles?
Pruning brings air and sunlight to the stems (called canes) so they dry rapidly following dew or rain; quick drying prevents diseases. Left alone, brambles spread vigorously, and pruning also keeps them from taking over the rest of your garden. Pruning even makes harvesting the fruit less painful: rather than having to fight your way through a tangle of thorny canes, you can pick fruits splayed out for your convenience.
How Brambles Produce Fruit
Knowing how brambles grow and produce fruit can help you understand how to prune them. Although all kinds have perennial root systems, the canes are biennial: they die after their second year.
Brambles are grouped according to when they bear fruit:
Summerbearing brambles. Canes fruit only in the summer of their second year.
Everbearing brambles. A cane begins fruiting near its tip toward the end of its first season, then in the summer of its second season the cane finishes fruiting lower down. Because new canes grow from ground level each year, both kinds always have both 1- and 2-year-old canes, so the patch fruits every year.
When and How to Prune Brambles
Prune out old canes. The descriptions above offer clues to one step in the pruning process. When canes have finished bearing their summer crop, or sometime before your bramble patch wakes up again the following spring, cut to the ground any canes that have completed their second growing season.
How do you recognize those canes? Their old, cracking bark and the remains of fruit stalks make it easy to identify them. They look dead because they are, or nearly so.
Selectively prune excess new canes. Brambles send up so many new canes each year that they can become overcrowded, so you must also cut some of the new canes to the ground. Do this while the plants are dormant, ideally just as the leaf buds swell in spring, allowing you to see which, if any, canes suffered winter damage. First, go after new canes that have spread too far. Lop them to the ground to keep the row no wider than about 1 foot across.
Prune out unhealthy and crowding canes. Once you've narrowed the row, further reduce the number of canes. If your plants form a continuous row, prune so that the plants are at least 6 inches apart. If plants are spaced along the row-3 to 5 feet apart, for example-reduce each clump to 6 to 10 canes. As you lop, always spare the thickest and healthiest canes. Look for and remove all canes with gray disease splotches or swellings caused by borers. To prevent borers from spreading from pruned to healthy canes, dispose of prunings well away from the bramble patch, or burn them.
Prune to promote growth and make harvesting easier. I divide summerbearing brambles into three groups to describe the next pruning step.