If you suround your trees and shrubs in your garden with a row of stones, e.g. with a row of construction stones, you could get a lot of ants under some of these stones in few month time.

If you don't have the time to turn the stones every month and scratch the earth under the stones , then likely in 3 month or less , ants will make their nest under some of the stones and from there go to the plants.

You better leave the stones away and make a sandhill round the plants.