How to grow blackberries
We’ve been eating (and trying to control them) for a century. Here’s how to enjoy the fruit without being overrun by thorny brambles, writes Rachel Clare.
Everyone has a blackberry story. Ever since Rubus fruticosus was brought to New Zealand by English settlers in the first half of the 19th century, their tart sweetness has prickled its way into our national consciousness.
As a child growing up in the 1920s in Weymouth, on the eastern side of the Manukau Harbour, blackberries were the main fruit my grandmother’s family ate.
Writing down memories of her childhood towards the end of her life, she described how she and her three sisters would pick them by the kerosene tin full. Their mother made blackberry and apple sponge puddings and filled the scullery shelves with blackberry jams, jellies and preserving jars full of them.
Elsy, the oldest of the four girls was the best picker of them all and managed to pick and sell 10 shillings worth so she could buy the sleeping doll she’d seen advertised in the Farmer’s Trading catalogue and had longed for.
While blackberries provided free vitamin C and income, by 1925 they’d become such a thorny problem, that the government offered a £10,000 reward for a method to successfully eradicate them. Despite this lucrative reward, blackberries are here to stay and have noxious weed status in most of New Zealand today.
They spread in several ways. Flung out from the crown, the arching canes take root when they touch the soil. They also produce rhizomatous stems underground. Birds spread the seed too. If you want to eradicate wild blackberry, check out Weedbusters’ advice here.
How to grow
Fortunately, cultivated blackberries, available at your local garden centre, are better behaved than the noxious sort (they’re thornless too!) but are slower to get going. Plants start producing from their second year, increasing to full production after three years. The fruit is usually harvested over a four to seven week period in late summer.
Four upright blackberries per family of four should suffice.
Keep their soil moist in summer with mulch, and feed annually with a fruit fertiliser to maintain their vigour.
Pruning
To keep plants tidy and productive, blackberries are best pruned in winter after fruiting.
Remove old canes (they will look woody, with yellowing leaves), and train in the new canes (or primocanes). Cut off the ends and train the stems in a fan shape or along horizontal wires.
Some people train all last year’s canes to one side and tie in all the new growth in the opposite direction to easily separate old and new.
In more confined spaces you can allow them to twist and meander about, rollercoaster style, along the support to pack in maximum fruit next year.
Unlike their unruly wild cousins, which have a trailing habit, cultivated blackberry varieties have upright growing canes.
Allow the new canes to reach metre, then cut to encourage branching for more fruit on the tips of each lateral. You can use manual or electric hedge trimmers to make it quick and easy if you prefer.
Propagation
Summer is the time to propagate. Take an end of a healthy cane, bend it down to the ground and bury the tip into the soil. By autumn you can cut the rooted tip free of the parent, dig it up and replant where you want.
Varieties
Thornless cultivated blackberries available from your garden centre, include ‘Navaho’, which shows good tolerance to heat and cold, and ‘Black Satin’, which has long, smooth canes that can be easily espaliered along wires. Or try boysenberry/loganberry hybrid, ‘Thornless Jewel’.
Pests and diseases
The main issue you’ll face with blackberries is protecting them from birds and bugs.
Green shield beetles will sink their fangs into the inky sacks, robbing berries of juice, while birds filch any they see. Fling bird netting over the canes or build a large berry frame with insect mesh to keep the competition out.
Harvest
Once your mouth and hands have turned blue from gorging on fresh blackberries, freeze them (perfect for smoothies), preserve them, add to puddings, or make jellies and jams.