Revenge of the Paulownia Tree
I recently had a paulownia tree clump of three trunks removed from near my house. I cut them down because one trunk had fallen in a storm and the other 2 became unstable, threatening to fall on the house. Within a short time, many shoots began popping up from the roots of the trees. These shoots grew with amazing speed. So I had the stump ground out but the shoots keep coming up with a vengance, sometimes growing 6-8 inches a day! I have sprayed them with herbacide to no avail. Is there any way to kill these roots once and for all?
Like many non-native invasive plants, paulownia has a big root system with enough energy stored there to keep coming back repeatedly when you try to kill it. Your choices are to exhaust the root system and/or use a systemic herbicide to get down and kill the remaining root. It is possible to kill the tree, it just requires patience and persistence. Think of it as a military campaign with many battles. At this time, keep cutting off suckers so they do not have time to photosynthesize more carbohydrates (more energy.)
For more information on using chemical herbicides, here is an excellent fact sheet at Weeds Gone Wild: http://www.nps.gov/plants/alien/fact/pato1.htm