I live next to a Washington Department of Transportation I-5 easement land where the department has let blackberries run rampant. As a result, I have thousands of blackberry seedlings in two areas of my property at this time of year. Is there any effective way to kill them at this stage?
In King County, Himalayan blackberry is a Class C noxious weed, meaning that control is not required by law, but is recommended in natural areas and restoration sites.
University of California, Davis Integrated Pest Management describes various methods of controlling blackberry.
In Ann Lovejoy’s Seattle P-I article dated, Thursday, June 7, 2001, she describes vinegar-based herbicide as a means of controlling weedy blackberries and horsetail.
You may also want to contact WSDOT’s roadside vegetation maintenance department to report the problem with unwanted blackberries migrating onto your property.
Another option, increasingly being used for large areas with invasive weeds, is to rent goats, who will eat the weeds down to the ground. The Seattle Post-Intelligencer published an article on this subject in 2007. “Rent-a-Ruminant” on Vashon Island is one example of a goat rental service.
This summer, I have been picking Himalayan blackberries in a local schoolyard. Twice in the last month, I developed sharp pains in my hand immediately afterward. There must be some type of neurotoxin in the bushes because the pain cannot be attributed to any cuts or scratches and is much more intense than a standard rash. What part of the plant could cause that reaction?
I checked Botanical Dermatology (Mitchell & Rook, 1979), Plants That Poison (Schmutz, 1979), the Plants for A Future database, and Toxic Plants of North America (Burrows/Tyrl, 2001) and found no references to any toxicity. Medical Botany: Plants Affecting Human Health (Lewis, 2003) describes the use of a blackberry-leaf tea for settling the stomach, so the leaves, when steeped, are not toxic. You do not say whether the pain is superficial, such as a skin rash, or deeper, which would make me wonder about some kind of stress or overuse syndrome.
Since we cannot give medical advice, you should discuss the incident with your health practitioner to see if you have some sensitivity to Himalayan blackberry, or to something else you encountered in that area. I found this link (to a page called Native Plants of Montara Mountain) showing the similarity in appearance between Himalayan blackberry and poison oak. It might be that you encountered poison oak without knowing it.
It may be that some other environmental factor (perhaps an application of herbicide) caused your distress. You should check with the school’s grounds supervisor to be certain.
Eradicating blackberry vines may seem hopeless, especially if you don’t want
to use chemicals, but don’t give up just yet. The Northwest Center for
Alternatives to Pesticides advises gardeners to cut off the top growth, dig
out the main root-ball, and then follow-up by mowing all new growth.
Planting desirable plants to shade out the sun loving blackberries is also
critical. Read the NCAP’s blackberry management plan (pdf).