How do I support thornless blackberries and when is the best time of year to prune them?
Like raspberries, blackberries produce canes that are fruitless during their first year, but which go on to produce berries in their second year. Once the fruit has been harvested from these second year canes, they can be cut down to the ground, leaving the first year canes to mature for next year's crop.
Blackberries come in three basic types: erect, semi-erect, and trailing. Thornless blackberries can belong to any one of these types. Erect blackberries possess sturdy, self-supporting canes that require no trellising. The semi-erect and trailing varieties both need to be trained along a wall, fence or trellis, otherwise you'll end up with a gangly, snarled mess that's more of a challenge than it’s worth.
In general, the thornless varieties are recommended for home gardens for a couple of reasons, the most obvious one being that you can train, prune, and harvest fruit from the canes without ending up looking like you just lost a fight with an alley cat. They are also slower growing than their thorny cousins, making supporting them less of a task.
To trellis them, you need to sink two ten foot poles into the ground approximately ten feet apart. Then you need to string four wires horizontally between those two poles. The lowest wire should be strung at the three foot level, the highest at the six foot level, and the remaining two should be strung, equally spaced, between the first two.
You’ll then train the fruiting canes in a fan shape, securing them to the wires. Any canes that extend above the top wire can have their tips clipped.
As the season progresses, first year canes will develop. Train these canes straight up and tie them in place so that they are out of the way. Once you’ve finished harvesting this season's berries from the fruiting canes, you will then cut them down to the ground and lower this year's canes into position, creating a new fan that will hold next year's fruit.
Keep in mind that thornless blackberries have a tendency to develop thorny canes over time. These canes must be clipped out as soon as they appear. If left unchecked, the more vigorous thorny canes will eventually dominate, slowly transforming your thornless blackberry into a thorny one.
If you have any questions or comments, please send them to me at vanessa@gardenmuse.ca.
