Spring is perfect time to wrangle blackberry vines

Published on Wed, Apr 13, 2011 by Naomi Knowlton

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I’d just settled in with a cup of tea and a novel when a loud, whacking sound disturbed my concentration.

I shook it off as I would a bothersome mosquito and tried to concentrate on my book. The repetitive sound became unbearable until I surrendered, put on my shoes and went out to investigate.

As I turned the corner of the house into the backyard, the culprit was in full swing—the Beast of Burden was taking out all his aggression on blackberries.

I can understand his frustration. Himalayan blackberry (or rubus discolor) is highly invasive. It has thick sprawling canes with piercing thorns that can reach up to 15 feet tall and produce trailing canes 40 feet long.

The trailing canes root at the tips, producing a thicket of thorns and brambles. To identify Himalayan blackberry, look for small white to pink flowers, edible black fruit, and leaves that are large, rounded to oblong, with toothed edges, and usually in groups of five.

Although Himalayan blackberry produces delicious fruit, its one benefit is dwarfed by otherwise noxious attributes: It outcompetes the native understory, prevents native trees from establishing, limits the movement of livestock, increases flooding and erosion potential, and can completely cover entire stream banks and channels.

Although Himalayan blackberry is invasive and damaging, there is plenty you can do to eradicate it. You can manually remove the plant—start with a small area and keep working outward. Cut the canes with pruners and dig up the remaining root ball. Be sure to remove all vegetation and fragments as seeds can remain in the soil for several years. Start soon, since the larger a blackberry patch gets, the harder it is to get rid of it.

Mechanical methods such as mowing can be practical in controlling larger blackberry patches, although it may take a couple of years to completely destroy the plant. Mulching the cuttings is also recommended.

Be careful not to mow on wet sites or those susceptible to compaction or erosion.

You may have to repeat mowing in later years as the plant may sprout from a root crown and give you greater density than before.

Herbicides can be highly effective at controlling Himalayan blackberries, particularly if combined with manual control. Master Gardeners have found that if you manually cut the cane down to within a few inches of the ground, and apply a few drops of herbicide directly on the woody stem, the blackberries die back. Leave them in place for a couple of weeks until they have died completely before removing. Always be extremely careful handling herbicides—many are non-selective, injuring or killing any foliage they come in contact with. If the blackberries are growing beside your prize tree peony, avoid getting the herbicide on its leaves.

One or all of these methods of control—manual, mechanical, and/or chemical—can help you get rid of your invasive Himalayan blackberries. I am going to work on mine as well, if I could only control the actions of the Beast of Burden.

For more information, contact the Master Gardeners at Washington State University’s Whatcom County Extension office at 360/676-6736.

Send your gardening questions or dilemmas to the garden guru at The Northern Light at info@thenorthernlight.com.