Thanks to Pat and Travis for your suggestions. You have given me the motivation to communicate with local neighborhood groups to deal with the tree of heaven in an organized fashion.
Yesterday I also noticed a number of these trees growing in the freeway landscaping near downtown Los Angeles. I spotted over 100 young A.altissimas in only one quarter mile stretch of the freeway. CalTrans also needs to take notice of this rapid infestation of the tree of heaven.
_____ Talk about weeds: World of Weeds
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Nature makes plants, humans make weeds.