I still have four seed bombs left in a baggie in my purse.....just waiting for the right spot. 8-) (and yes I did make sure there were no invasives in them.)

In the Portland case I linked to above, the parking strip was on property occupied by a religious organization who had contracted with a parking lot operator and that operator did send out a person to pull out all the vegetable plants. I would think every square foot of downtown Portland is under occasional monitoring by some business or company and any guerrilla garden is unlikely to survive.

The closest I've gotten to guerrilla gardening was to throw some mosquito dunks into a big low spot where my former neighbors used to have an above ground swimming pool. They took it down, but didn't do a good job of filling in the big round depression left by the pool, so it filled up with water whenever it rained. It was a perfect mosquito breeding place. So, I got some mosquito dunks and chucked them over the fence into the "pool". DH thought it was an inappropriate thing to do, but I didn't care. The dunks are not toxic, so I figured no one would be harmed, except the potential mosquitoes. There was a time when I was trying to get rid of tawny daylilies, and my neighbors got tired of me asking if they wanted some. If I had read this thread way back then, I might have gotten an idea of what to do with all those daylilies! Sally

I will also use my weed popper on the dandelions in my neighbor's yard. The people on our west side will mow, but don't do anything about the weeds, no trimming of shrubs and don't even edge along the sidewalk or curb. It is a constant battle trying to keep their weeds under control when they get close to my garden. I actually have edging all the way down the property line just inside on our side and will take our string trimmer and scalp their stuff to the ground up to 5 inches away from the edging. My next job is to trim their bradford pear in the back corner of their yard that is severely hanging over the fence onto my garden - not to mention putting weight on the fence that we replaced three years ago. If it is hanging over on our side, it gets cut.