Answer: The mint is not the problem, Texas is causing your cherry tree to die! Montmorency is a wonderful pie cherry, and the best for attempting south of "cherry country", but it just wants to be further north. The l-o-n-g, HOT summers are really tough on cherries.
If the alkaline soil is causing a problem it will show up as iron deficiency, yellowing leaves at the ends of new growth.
Clay soil and poor drainage is really tough on stone fruit like peaches, plums and cherries. If you want to give a Montmorency a fighting chance in your north Texas location, plant it on a mound of improved soil about 1 foot high and 10 feet wide (four old railroad ties make a suitable bed) filled with your soil amended 50/50 with compost. Hope you can beat the odds (isn't that what we gardeners love to do!) and be the first to take a cherry pie to the local garden club meeting!
Q&A Library Searching Tips