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Tales from a Plant Addict

Fun (& a few serious) facts, tips and tricks for every gardener, new and old.

Pruning Blackberries vs Raspberries


It may sound strange, but blackberries are a fruit I don't remember eating much as a child. I grew up eating raspberries in our home garden, but never blackberries. I am from northern Illinois, and most blackberries aren't reliably hardy there. A good cultivar for colder climates is 'Illini Hardy'. University of Illinois developed this very cold hardy cultivar, which produces great tasting fruit if you can manage to get past the millions of thorns on its canes without losing a pint of blood.

I much prefer the thornless blackberry cultivars, the first of which, 'Everthornless', was developed at University of Illinois by one of my favorite professors, Dr. Bob Skirvin.

I have one thornless blackberry cultivar in my garden, called 'Triple Crown'. One year in the fall I decided to pay these plants some extra attention in an attempt to boost my harvest the following year. In my excitement I ignored some important details on how blackberries grow differently than my raspberries.

Blackberries and raspberries are perennial crops, but the shoots, or canes that grow are individually biennial. That means that each individual cane will only live for two years.

The first year of growth, the canes are called "primocanes". In blackberries and some raspberries, the primocanes do not produce flowers and fruit. In the second year of growth, the canes are called "floricanes" and they produce flowers and fruits. If you just let blackberries and raspberries grow without pruning or cutting back, there would be a mixture of primocanes and floricanes present at any given time.

There are raspberry cultivars available that are called primocane fruiting or autumn fruiting types. These will flower and set fruit on the primocanes, which means you can harvest fruit from them the first year they are planted. They will set fruit on the same canes in the second year (now called the floricanes), but in general this second crop is of lesser quality. These are the kind of raspberries I have in my garden.

Recommended pruning for blackberries and raspberries in spring is to remove the dead canes, leaving both primocanes and floricanes intact. Remember that floricane fruiting raspberry cultivars and all blackberries must be pruned this way if you want to harvest any fruit—they only produce fruit on the floricanes, so you can't remove those and expect to harvest any fruit!

Autumn or primocane fruiting cultivars may be cut back to the ground after last harvest in the fall. This channels all the plant's energy into producing primocanes the following spring, which for these types yield the best quality fruit. It also reduces the chances of diseases overwintering in plant debris.

This is where my big mistake comes in. Back in 2008, I took a deep breath and mowed my raspberries down to the ground. They are primocane, or autumn fruiting types. So all that came up the following spring was primocanes, and I had a bumper crop that year as expected. That's the good news.

The bad news is that I mowed my blackberries down the same way. I forgot that although there were a lot of floricanes which flowered and produced fruit that year and should have been removed, there were also plenty of primocanes, which would have produced fruit the following year, had I not mowed them down the previous fall.

I should have only removed the canes that had flowered and produced fruit in that year, then in early spring trimmed away any parts of the primocanes that had been killed by winter cold. The ends of blackberry canes are prone to winter kill, so pruning should wait until the spring.

Instead all I had was a tangled mass of primocanes that year, wondering where the fruit was. I left them alone that fall, and the following spring trimmed them to a manageable height of about four feet tall. Since the plants had an unexpected vacation from producing fruit the previous year, I did have a nice crop the following year.

This year I am looking at the other end of the spectrum, at a berry patch that has been horribly neglected. The blackberries have carried on, and rooted everywhere their arching branches touch the ground. Normally the trellising they are on prevents this, but they have overgrown it. In trying to look at the bright side, there should be plenty of fruit this year, as the plants are growing everywhere it seems!

The raspberries are not as productive as they are in years when I mow them down in the fall. But remarkably there are still quite a few fruits. My son has quickly learned what a ripe raspberry looks like—and I don't mind the neglected berry patch as long as I get to see his face light up when he eats a ripe raspberry!



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