Ceterum censeo...okay so maybe I'm not the great Roman senator and orator Cato (I have an extra N in my name) but you get the idea. The biggest foothold I see the
highly-invasive non-native fennel gaining in Rose Canyon is out there at the west end, on the side (uphill) side of the canyon. If you see broken stalks out there that would be my handiwork. Chopping at this stuff was a lot more fun than it should have been. My sword ran with the blood of the fennel! That is, the stick I used now smells licorishy. I've pulled this stuff out before so I have no illusion that one such treatment will kill it, but repeated thrashings usually do the job.
If you're comfortable with your ability to identify this plant and you see more growing in open spaces, please feel free to join me in fennel genocide. (Fennecide?) And if you like it in salads, take some home! (I can't stand the stuff; plus it contains phytoestrogens, yikes!)