Berry bushes such as raspberries and blackberries are generally referred to as “brambles”. By knowing a few facts on how they grow, you will be able to prune them easily, keeping your berry patch productive for many years. For most gardeners just growing raspberries, the main pruning to keep in mind is to cut out canes after they’ve fruited, and to thin out canes early each summer to 6 inches or more apart.
Proper pruning is perhaps the main point to making sure you have good yields, assuming of course that you’ve chosen selections that are hardy in your area. Without pruning, your berry patch will fill with old canes and both plant vigor and yields will go down. With proper pruning, you should get good harvests from your bushes for 10 to 30 years.
Since most brambles have thorns, a useful tool is a pair of long-handled pruners in addition to regular hand pruners. I also like to use rose gloves—those with long gauntlets to protect your arms. Once pruned, remove the debris away from plants, to the landfill, or burn as insects love to live in such shoots.
Raspberries come in two types—those that bloom on canes (those shoots from the ground) that were formed last year (sometimes seen as “floricanes”), and those that bloom on canes that form the current year (also called “primocanes”). Most the raspberries you’re familiar with that fruit in mid-summer are the former, or “floricane-bearing”. This is important to know since if you cut the canes after only the first year, you won’t get any fruit. And, after the second year-old canes fruit they wont fruit anymore, so can be cut off at ground level—either after fruiting, in fall, or the following early spring. You can tell these older canes as they are generally a light brown, brittle, and more woody.
The other type of raspberries includes those that fruit some in summer, but again in fall. For this reason they may be called “two-crop” raspberries, or “everbearers” although this last name is misleading. The fall crop is produced on the primocanes from that current season. I like to prune off all shoots to the ground in spring, sacrificing any summer fruit but allowing all the plant energy to go into producing a larger fall crop.
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 so 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 canes each year, along with those that are damaged or crossing, you’ll want to thin out canes. Brambles tend to spread where you don’t want them and to get too thickly crowded. Too many shoots results in reduced air flow and better chance of diseases. Also, too many shoots results in 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 (homefruitgrowing.info) or from the Fruit Gardener’s Bible by Lewis Hill and Leonard Perry.