Let's begin with defining what a noxious weed is: "Aggressive exotic plants can produce immense numbers of long-lived seeds and may overwhelm native species, degrade habitat for wildlife, stick, stab and poke, and may even poison livestock or burn your skin. " Noxious weeds are great at reproducing and are so pernicious, that many are mandated for removal in Washington and King County.
There are several classes of noxious weeds and they require different amounts of attention and handling.
I. Regulated Class A noxious weeds (eradication required throughout Washington State including King County)
Examples are kudzu and milk thistle
II. Regulated Class B noxious weeds (control is required for these species in King County)
Examples are poison hemlock and tansy ragwort
III. Non-regulated Class B and C noxious weeds (Class B and C noxious weeds that are not designated for control in King County, control recommended but not required in King County)
Examples are Himalayan blackberry, from Iran and Armenia NOT the Himalayas and butterfly bush.
Nuisance weeds are those that interfere with YOUR gardening goals. Often these weeds have anatomy much like those of noxious weeds that allow them to spread quickly and remain in your garden year after year.
They have thick tap roots that are hard to pull or dig up fully. They may spread via miles of underground stolons and rhizomes like quack grass and bindweed. They may also send up hundreds if not thousands of seeds per season. Do you recognize these weeds from Marymoor Community Gardens?