Fellow West Coast flame weeder here! Our weeds are especially tenacious, for the reasons you've described and for our boom/bust water cycles. They tend to sto

Fellow West Coast flame weeder here! Our weeds are especially tenacious, for the reasons you've described and for our boom/bust water cycles. They tend to store enough excess carbohydrates in their roots to re-sprout three or four times. While this can make them seem utterly invincible, they will in fact deplete their resources if you stick with it long enough. I usually plan two or three flame weeds during spring, followed by some later touch ups if fire season allows. (Always wet the ground beforehand if it's dry out). This also works with weed whacking. Himalayan blackberries, for instance, seem to only be able to resprout two times. So I knock them down as low as possible with a hedge trimmer, then touch up the new growth with the string trimmer about six weeks later, then again six weeks after that.