By Caroline Cox, 2003; Updated 2019

Many Northwesterners have conflicting attitudes about wild blackberries. A handful of ripe berries or a piece of fresh blackberry pie is a scrumptious treat. On the other hand, it’s easy to hate the brambles that take over a back fence or a creek bed.

If you decide to get rid of unwanted blackberries, you’ll be faced with a resilient and thorny plant. It’s not true that removal of these plants “must rely on foliage-applied herbicide treatments.”¹ With a little persistence you can remove unwanted blackberries without using chemical poisons.

Basic Biology

The common weedy blackberry in the Pacific Northwest is the Himalayan blackberry, Rubus discolor. Despite its name, it is a native of Europe. It is widespread in southern British Columbia, Idaho, Washington, Oregon, and northern California and is also common in the northeast U.S.² It thrives in disturbed moist areas and at all elevations up to 5,000 feet.³

Blackberry branches, called canes, are known for their stout thorns. Canes are biennial, producing lateral branches which bear fruit in their second year.²

Himalayan blackberries are robust. They can be 10 feet tall and their canes can grow as much as 20 feet in a season. Trailing canes can root where they contact the soil, producing “dense, impenetrable thickets.”²

At the base of a blackberry cane is an irregularly shaped crown. Roots extend from this crown, and have been recorded up to 30 feet long!⁴

Blackberry seeds are transported by birds and mammals that eat the fruit. Seeds can remain viable in the soil for several years.⁵ New plants can also develop from crowns and underground stems.¹

There are several native blackberry species in the Northwest.³

Focus on Desirable Plants

Start a blackberry removal project by thinking about what plants you want in the area that’s now blackberries. Planting desirable seeds or nursery stock once the berry plants are removed is often critical.

Blackberry removal techniques are site specific. What works well in one site might not be compatible or effective at a different site. Choose a technique that fits in with your goals for the site after the blackberries are gone.

Don’t Get Discouraged!

Many of the characteristics of the Himalayan blackberry make this plant difficult to remove. Don’t get discouraged when you tackle a blackberry removal project without herbicides. Remember that, according to the University of California, “blackberry plants usually regrow following herbicide application.”¹ All techniques for removing blackberries require persistence. Plan to follow up your removal work.

Don’t Forget Disposal

All blackberry removal techniques (except grazing) will leave you with dead or dying plant material, most of it thorny. Before you start, figure out how you will cope with this material. In an urban setting, your own compost pile is a good solution. Alternatively, find out if your community offers a composting program, or if a local business accepts yard waste for composting. Then decide how to bundle and transport your material.

In natural areas, the waste material can be piled and left to decompose. Sprouting from these piles is rare, and the piles will disappear relatively quickly.⁶ Smaller amounts of blackberry stems and crowns can be piled on logs, or hung from trees to dry out.⁶

Removal Techniques

Whatever removal technique you choose, be sure to protect yourself from thorns. Leather gloves, sturdy boots, a long sleeved shirt, and jeans or other tough pants are all essential.

1.    Mowing & Cutting

One technique for removing unwanted berries is mowing or cutting. Mow, cut, or brush hog the vines to ground level. Continually cut back new sprouts to eventually kill the plant. If you’re trying to turn a blackberry patch into lawn this is an ideal technique. The repeated mowing that your lawn requires, along with the competition from grasses, will choke out the blackberry plants over time.⁷ In a small area, loppers or weed whackers can substitute for a mower.

Covering the soil after cutting or mowing can be an appropriate way to kill roots and crowns. A thick dark material will keep light from reaching new sprouts from roots or crowns so they can’t grow.⁸ Use this technique to transform, for example, a blackberry patch into next year’s garden.

2.    Digging

Digging out blackberry crowns is another effective removal technique. The Nature Conservancy calls digging blackberries “a slow but sure way of destroying”⁹ this plant. This technique, which specifically targets blackberries, is useful in areas where preserving the neighboring vegetation is important.

In Oregon’s Tryon Creek Natural Area, enthusiastic teams of volunteers led by two dedicated coordinators are successfully removing blackberries from large areas using this method. Volunteers (nearby residents, employee teams from a local utility, and county community service crews) provide the labor. According to coordinator Dave Kruse, effective digging doesn’t take special techniques. He tells the volunteers to dig out the crown and tells them they don’t need to worry about all the little roots. Generally, they have found that persistence determines success. They don’t clear areas that they don’t have time to maintain. They go back about a year after the original dig and remove any new plants. Typically the number of blackberries at that point is about 1/4 of the original amount, but they are easier to dig because they don’t have large crowns. After that work is done, they find they only have to check on an area about once every three years. They also plant native conifers in newly-cleared areas, since blackberries don’t thrive in shady areas. In four years, the volunteers have taken care of most of the blackberries in half of the 645-acre park.⁶

Digging blackberries doesn’t require any tools other than an ordinary shovel or spade.⁶ However, some diggers have found a claw mattock useful. The “claw” pulls out plants like a claw on a hammer pulls out nails.⁹

3.    Goat Grazing

Goats have a long history of use for blackberry control, particularly in Australia and New Zealand. Goats eat blackberries readily, and seem to prefer them over other plants. An economic analysis in Australia showed that running goats on a blackberry-infested pasture was cheaper than using herbicides to manage the berries.¹⁰ Clearly goats are not suitable in all locations, but in pastures they may be an excellent option. Use of goats could also be considered in firebreaks,¹¹ utility rights of way, and other similar sites.

Conclusion

Many people in the Pacific Northwest sympathize with the Oregon resident who reputedly said, “If we all left the valley, in three years Himalayan Blackberry would prevent us from getting back in!”.² However, with an understanding of the biology of this weed and a little persistence, it is not difficult to manage blackberries without pesticides.

For expert advice tailored to your pest or weed issues, check out our sliding scale Pest and Weed Management Consultation services.

References

1. University of California, Agriculture and Natural Resources. 2010. Wild blackberries. http://ipm.ucanr.edu/PMG/PESTNOTES/pn7434.html
2. Oregon State University Horticulture Department. Landscape plants: Rubus armeniacus. https://landscapeplants.oregonstate.edu/plants/rubus-armeniacus
3. Ertter, B. 1993. Rubus. In The Jepson manual: Higher plants of California, ed. J.C. Hickman. Berkeley: University of California Press.
4. Amor, R.L. 1974. Ecology and control of blackberry (Rubus fruticosus L. agg.) Weed Research 14: 231-238.
5. Brinkman, K.A. 1974. Rubus L.: Blackberry, raspberry. In Seeds of woody plants in the United States. Agriculture Handbook No. 450. C.S. Schopmeyer, ed. Washington, D.C.: Forest Service, U.S. Department of Agriculture. Pp. 738-743.
6. Interview with D. Kruse and P. Hamilton, Friends of Tryon Creek. Portland, OR. Feb. 5, 2003.
7. Tall Clover Farm. 2011. Brambles gone wild: How to remove blackberries. https://tallcloverfarm.com/3547/brambles-gone-wild-how-to-remove-blackberries
8. Drliik, T. 1996. Stumps and brambles. Common Sense Pest Control 9:21.
9. The Nature Conservancy. 1989. Elemental stewardship abstract for Rubus discolor (Rubus procerus), Himalayan blackberry. https://www.invasive.org/gist/esadocs/documnts/rubuarm.PDF
10. Vere, D.T. and P.J. Holst. 1979. Using goats to control blackberries and briars. Agricultural Gazette of New South Wales 90; 11-13.
11. Kiester, E. 2001. Using goats to prevent wildfires. Smithsonian Magazine (October). https://www.smithsonianmag.com/science-nature/using-goats-to-prevent-wildfires-51327045/