Organic removal methods are commendable on small plots with easily-pulled invasives (and worth the peace of mind), but the invasive battle may require herbicide assistance to control weeds that regrow with 20 times the stems if manually cut (particularly holly, knotweed, blackberry). Grubbing (digging out) Scotch Broom, blackberry, holly and laurel is possible, but it can leave soil scars that erode soil and invite weed seeds. It’s questionable whether such methods will ever get ahead of reinfestation rates.
If you decide to do-it-yourself using herbicide (on your property only), be sure that you’re not in an Environmentally Critical Area (click the link, plug in your address, click the ECA tab, and if any category shows “yes”, then your property is designated an “ECA”). If so, review the City’s ECA permit requirements, including the Client Assist Memos, CAM 331 and CAM 331A.
King County Noxious Weed Control Program has many resources for best control methods, including classes and tools for knotweed injections. Be certain you can distinguish noxious alien plants from native, and that you read and follow the pesticide label. Of course, establishing native plants will help prevent the return of noxious weeds, and King County’s Native Plant Guide has great landscaping plans and tips for choosing plants appropriate to your site. Again, inexpensive bareroot plants can be ordered (every January) through King Conservation District.
Professional restoration companies (listed left) can help choose the least toxic, most effective alternatives for invasive removal (they work in this field because they care about environmental health – and they sometimes recommend herbicides). Professionals can help identify plants and share their experience to assist your own efforts.
Other companies not listed may be qualified to help, but you should check to make sure any company has up-to-date pesticide licenses.