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  • Anna Hammond

Blackberry Knockdown from Snow to Sun

The team here at Habitat Restoration Specialists spent a few weeks tackling a massive blackberry patch stretching along a road under some powerlines, alongside a forest buffer and some fences. By the end of our time on this large site, we had cut down about 136,000 square feet of blackberry!


HRS owner Derek working his way through the blackberry patch with a hedgetrimmer.

The preferred tool for knocking down blackberry for us is the hedgetrimmer, as it allows us to work much closer together without flying debris (like with a brushcutter), and has a longer cutting edge. The hedgetrimmer also is a much more precise machine that can be more easily navigated with to cut invasive plants closer alongside native species with less risk of harming the native plants. With some time learning and perfecting your technique (which I can guarantee you we had ample of with the time on this project!), you develop a sense for how to approach the blackberry stands to most efficiently cut the canes with the least effort.


HRS employee Kayli using the hedgetrimmer to cut blackberry bushes back.

The goal here is essentially to create access for us to bring backpack sprayers in to spray the regrowth with herbicide. It's necessary to knock the blackberry down to the ground first for many reasons.

  1. If you don't knock the tall hedges of blackberry down, you can't even walk through much of the patch in order to spray enough blackberry to kill the plants. It's recommended to achieve 90% leaf coverage while spraying herbicide, and we definitely couldn't do that with the patch fully grown with multiple years of dead growth blocking access.

  2. If we didn't knock the blackberry down first, we would have to use a significantly higher volume of herbicide (and water) in order to achieve the 90% coverage over much larger plant surface area! Only spraying regrowth allows us to use the most minimal amount of herbicide and water necessary in order to treat the plants, which reduces the impact of the chemicals in the environment and is much more precise, reducing runoff to the soil and off-target spraying!

  3. By "mulching" the canes down to pieces around 2 feet long, they will decompose quickly, giving their nutrients back to the soil.

  4. Cutting the canes down small is also ideal so they present less of a tripping hazard when you return to spray the regrowth with herbicide. Between the length of the canes and their nasty thorns, it's definitely worth the time and effort to cut them down small to prevent the trips and falls which are even worse while carrying a heavy backpack sprayer.

  5. We leave 1-2 feet sticking up from the "root ball" of the blackberry, and this is where the blackberry will continue to make new growth. After 4 weeks or so, there will be some fresh leaves here, which will be very easy to achieve 90% spray coverage of the surface area. Spraying these leaves so close to the ground also reduces drift, guarantees you will only spray your target weeds and not any native species, and like I mentioned before, reduces the volume of herbicide and water needed!


Expanse of knocked down blackberry.

We had quite the variety of weather on this project, from beautiful sunshine with a view of Tahoma (Mt Rainier) to freezing temps with snow and hail!


We would like to acknowledge that we were working on the traditional occupied lands of the Muckleshoot and Coast Salish Peoples, who have been here since time immemorial and are the original stewards of this land.


March 15: Snowing


This project was funded through HeLP, the Healthy Lands Project. This is a program through King County with the King County Noxious Weed Control program. HeLP aims to provide invasive weed control and stewardship assistance on private and public lands in cities and unincorporated areas throughout King County, prioritizing areas on recently protected conservation lands and open space. When a site is approved for the HeLP program, there is no cost at all to the landowner- only the expectation that after weed removal, the landowner will work with HeLP or project partners to implement a stewardship plan that will sustain the benefits of the weed removal. For more information, and to inquire if your site could be eligible for assistance with the HeLP program, visit https://kingcounty.gov/services/environment/animals-and-plants/noxious-weeds/healthy-lands.aspx


himalayan blackberry being cut down alongside fenceline
Blackberry cut down up to the fence line of the neighboring horse pasture

Derek using the hedgetrimmer to cut blackberry among young native trees




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