Depth of Crepe Myrtle Roots

Question

I am going to plant Asian Jasmine under my Crepe Myrtles. I have put Round-up on the grass and want do till the soil and remove the debris. How deep underground should the crepe myrtle roots be on three year old trees, which have grown very well?

Answer 1

These trees do not have extensive root systems, but the Roundup should not penetrate that far into the ground as to harm the tree roots.