By Laural
United Kingdom 
I have for years been growing a tree which I bought at an open garden. It is now about 20ft high and lovely producing many small plants all around. I started to worry when one appeared in my conservatory at the wall adjoining the house. I plucked and killed with weed killer but am now worried about the foundations. I think it is Tree of heaven. I want it gone how to I kill it and its roots.. It is about 10 feet from the conservatory.
10 Nov, 2016
Answers
Saw it down as low as you can, then drill into the stump with a medium wood bit, making pits or wells about quarter inch deep, pour neat SBK (a brushwood killer available at Amazon or garden centres) into the holes without spilling it anywhere else, then cover the stump with something - an upturned pot, a sheet of plastic, a stone slab, whatever. That will kill the roots.
10 Nov, 2016
Over the next year or two, you may get other sprouts. If so, cut them off low, paint the cut surfaces with SBK, and put a piece of duct tape over the.
10 Nov, 2016
Many thanks for your response - Is there a best time of year to cut it down?
10 Nov, 2016
Now is good, as the sap is falling, not rising, but it can be done any time.
10 Nov, 2016
You are right to be worried - this is a very invasive specimen. I would try to cut the thick roots, but you probably need an expert . . . hopefully someone on this site will be able to give you helpful advice.
10 Nov, 2016