Berry bushes such as raspberries and blackberries are generally referred to as “brambles.” Knowing a few facts about how they grow will help you prune raspberries and blackberries easily, keeping your berry patch productive for many years.
Proper pruning is the key to good yields from blackberries and raspberries. Without pruning, your berry patch will fill with old canes, and plant vigor and yields will decrease. With proper pruning, you should get good harvests from your bushes for 10 to 30 years.
Since most brambles have thorns, it’s wise to use a pair of long-handled pruners and regular hand pruners. I also like to use rose gloves – those with long gauntlets to protect my arms. Once pruned, remove the debris away from plants, to the landfill, or burn it, as insects love to live in these shoots.
Two types of raspberries: Floricanes and Primocanes
Raspberries come in two types—those that bloom on canes (shoots from the ground) that were formed last year (called “floricanes,”) and those that bloom on canes that form the current year (called “primocanes”). Most of the raspberries you’re familiar with that fruit in mid-summer are the “floricane-bearing”. This is important to know because if you prune floricanes during their second season, you won’t get any fruit. But after they fruit, they won’t fruit anymore, so they can be cut off at ground level—either after harvesting in the fall or the following early spring. You can tell these older canes as they are generally light brown, brittle, and woodier. Thin out canes early each summer to 6 inches or more apart.
The other type of raspberries are those that fruit once in summer and again in fall. They may be called “two-crop” raspberries, or “everbearers” although this last name is misleading. The fall crop is produced on the primocanes from the current season. I like to prune off all shoots to the ground in spring, sacrificing summer fruit to allow all the plant energy to go into producing a larger fall crop.
When to Prune Blackberries
For purple and black raspberries and upright blackberries, “tip” or prune back canes in early summer. This keeps them from getting too tall and promotes more side branches and more fruit the second year. Prune off the top 3 to 6 inches when the canes are 3 to 4 feet high. If you’re using a trellis system for support, you can wait until they are about 5 feet tall to tip back.
Then, late next winter, in addition to removing any broken or crossing branches, prune or tip back the lateral shoots (those off of the main upright canes) to about 6 inches long (or for upright blackberries to about 12 inches long). As with the one-crop raspberries, prune out any canes that fruited the previous year.
If you are in a warm area and can grow trailing blackberries, such as the hardy (to zone 5) ‘Chester’ or ‘Triple Crown’, leave the trailing shoots on the ground the first year. They’re easily protected this way over winter with straw. Then, the next spring, train these second-year shoots onto a trellis. Measuring up from the base of the plant, cut off the lateral shoots from the lower two to three feet. For the rest of the laterals, where the fruit will be produced, tip them back to 2 to 4 inches long.
In addition to pruning out old blackberry canes each year, along with damaged or crossing ones, you’ll want to thin them out. Brambles tend to spread where you don’t want them and get too thickly crowded. Too many shoots result in reduced airflow, a higher risk of diseases, and fewer and smaller fruit.
So in early summer, cut out new shoots which are weak or thin. Cut out any new strong shoots that are closer than 6 inches apart, or 12 inches apart for the more vigorous blackberries. You’ll also want to cut out shoots that are coming up beyond a two-foot wide bed, if they’re not in a grassy strip that you keep mowed.
More on choosing brambles, other aspects of their culture, cultivars, and lesser known brambles such as the loganberry or boysenberry, can be found online at home fruit growing or from the Fruit Gardener’s Bible by Lewis Hill and Leonard Perry.
A version of this article appeared on the University Of Vermont Extension website.