Do you have any bark mulch up against your foundation? Because I have heard you should keep mulch at least 5 feet away from the foundation because ants like to shelter their cities under it and if it's close to your house, inevitably they'll just travel straight up the foundation and in through tiny cracks.
Excellent point. That's why cedar mulch is recommended not bark. Ants will make a bridge out of anything including bark/chips. That means no vegetation touching the house, no branches period no matter the flower, bush, tree etc.