Black berry removal
We need to remove a big area of established blackberries by the roots to minimize future growth? The property is in the scenic area of the Columbia River Gorge.
Multnomah County Oregon
By the roots is not a good idea, the pieces left behind all make new plants, We recommend a systemic herbicide that kills the whole plant rhizomes and all. The seeds last years so repeat applications will be needed to maintain the area.
Here is some information for you http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/19779/ec1594-e.pdf
here is more