Q.keep a Russian sage plant from spreading
How can I keep a Russian sage plant from spreading? New growth is popping up feet from the original square garden plot intended. IF I use a weed killer on the new shoots of Russian sage that are in spots I don’t want, will that kill the entire plant? Is it better to pull the new sprawling plants out of the soil?
Just clip off the unwanted plants.
Using a herbicide will kill the main plant, likely and the risk of accidental exposure to other plants is high.
https://www.gardeningknowhow.com/ornamental/flowers/russian-sage-flowers/russian-sage-care.htm