QUESTION: I love the idea of growing my own thornless blackberries, but I’m not the most experienced gardener. Are thornless blackberries hard to grow? — Janine T.
ANSWER: It’s true that growing thornless blackberries has a few extra steps, but none of those steps should be too difficult for you. Thornless blackberries aren’t really hard to grow. You just have to know what they need to thrive. Keep reading to find out what to do to make your thornless blackberry plants happy and productive.
Tips for Growing Thornless Blackberries
- For the biggest blackberry harvest, situate your thornless blackberry plants in a spot where they will get full sun. (That’s six to eight hours of direct sunlight every day.)
- Getting the right soil is almost as important for your thornless blackberry plants as enough sunshine. Use a sandy loam that’s had coarse sand or clay added to it. The soil should be made up of at least two percent compost, shredded leaves, or other organic material. The best pH level for your thornless blackberry plants is slightly acidic: between 6.5 and 7.
- Space your thornless blackberry plants apart so that there’s plenty of room for sunshine and air to reach the foliage. Set their rows at least 12 feet apart. Erect thornless blackberries that are not trellised should be positioned three feet apart. Erect thornless blackberries that are trellised should be five to six feet apart. Semi-erect thornless blackberries get six to eight feet of space between them. Trailing thornless blackberries should be set a minimum of 10 feet apart.
- Unless your thornless blackberry plants are the erect variety, you’ll need to support them with a trellis, stake, or other system. Propping up the heavy branches of your plants when they’re weighed down with fruit will help ensure you get to harvest more of them. It will also be easier for you to reach the fruit when it’s time to harvest.
- Use a mulch to keep moisture available in the soil for your thornless blackberry plants and to balance out the soil temperature. Use the perpetual mulching technique, continually adding to a four-inch layer of organic material like shredded leaves, compost, or another mulch as needed. Mulch is best applied in the time between the beginning of fall and the end of spring.
Remember not to touch the mulch to the plants themselves. Instead, leave at least five inches of empty room between the base of a plant and the layer of mulch. If the mulch makes contact with the plant, it can contribute to the spread of plant diseases in your garden.
Pruning Your Thornless Blackberry Plant
The time of year that you should prune your thornless blackberry plant depends on the type of plant you have. But whether you’re growing primocane or floricane blackberries, you’ll know it’s time for pruning once the harvest is complete. (By the way, if you’re not sure of the difference, the first year of growth is on primocanes, while floricanes are the second year of growth.)
For floricane blackberries, the only pruning you need to do is on the two-year-old canes. As soon as you’ve harvested, you’ll see lots of action from the new growth if you trim the two-year-old growth. Prune close to the crown, also taking out any branches that are dead or look like they’ve suffered disease.
Primocane blackberry bushes will need pruning at a different time of year, around November when their harvest has ended. Unlike with floricane bushes, the two-year-old growth will come back the following spring if you prune all your floricane thornless blackberries down to the ground.
With primocane blackberries, you may have heard advice to pinch back new growth at the end of spring in hopes of getting more blackberries. You can take this approach if you like, but be advised that your blackberries will come in later in the fall if you do. For this reason, pinching your new growth black at the beginning of the season is only recommended for gardeners in zones 8 to 10.
You should use clean, sanitized shears to prune, because failing to clean your gardening tools can result in the spread of disease through your garden. After pruning, make sure to clean up any plant material that you clipped or has naturally fallen over the season. Do not add this plant material to your compost. It should be thrown away somewhere safe or burned.
As you can see, you’re investing a bit more time and energy in a thornless blackberry bush than you would with a succulent or houseplant. You’ll need to install a trellis as well as pick the ripe berries off the plant, then prune once blackberry season is over. But don’t let the idea of this additional work stop you from growing thornless blackberries. We’ve broken down the steps you can follow to grow a bumper crop of thornless blackberries.