Killing Weed Trees Mixed With Lilacs

Question

Three years ago, I moved back into a house I’d lived in as a child. The house was a rental for 27 years and the landscaping was indifferently maintained. Three lilac bushes that my mother planted in 1977 remain, but weed trees have grown in amongst the roots of two of them. I have twice cut the trees as close to the ground as possible, but I’m also active duty military and have been deployed over the last two growing seasons and the buggers keep growing back taller than the lilacs while I’m away. What can I do to kill these things without killing the lilacs as well?

Answer 1

Here is an article that you may find helpful: https://www.gardeningknowhow.com/ornamental/trees/tgen/weed-trees.htm