Hi Phillip! Thanks for reporting this. This looks like bull thistle to me. Milk thistle would have broader leaves with definite splashes of white.
As with all invasive thistles control is important. Yes, pulling by hand and then spraying the rosettes with RoundUp will be effective. This plant will die on its own after flowering, so you could just cut off the flowers and seed heads and skip the digging.

Here's our best management practices document.
https://tualatinswcd.org/species/bull-thistle/#docaccess-0a023a3925bb4abbc52bc58f40895c6f

Keith Nasman
Invasive Species Technician
Tualatin Soil & Water Conservation District
keith.nasman@tualatinswcd.org

Keith Nasman
Sept. 10, 2026, 11:28 a.m.