The Tree of Heaven (Ailanthus altissima) is admittedly a very tricky tree to maintain. We have been maintaining our for many years now. I have to say, it loves to create seedlings. The Tree has a long Philadelphia connection. From http://www.fs.fed.us/database/feis/plants/tree/ailalt/all.html
Sprouts from the first tree-of-heaven in North America, planted in Philadelphia’s Bartram Botanical Garden 1784, still existed at the turn of the 21st century
In Philadelphia, tree-of -heaven sparked the interest of amateur and professional horticulturists alike as a desirable and unique shade and ornamental tree for the gardens of larger home and farm landscapes
I have to admit it is a great shade tree and I can understand why people used it in cities where gardens were small and limited.
So why do I call it the gardening clock. If you get lazy at keeping your garden or yard cleaned and trimmed, this definitely reminds you of your gardening duties. You will start seeing little sprouts. I think this might be why people in Europe and America were so fascinated with the tree. They would see it in gardens in China that were well maintained. What they did not realize is that, it had to be done. So the tree became its own promoter because the gardens were so beautiful.
This tree does keep its owner on their toes, but it rewards with shade, filter light and a great wind block.