If there are many young plants of Verbena bonariensis coming up, it is best to remove them by hand. And you know what’s also nice? Even in winter, the spent stems of Verbena bonariensis can still look beautiful. So you might consider cutting them off only next spring.
Grows very well in a sunny spot, in soil that lets water through well, even if a bit chalky. Not a fan of heavy or wet soil in winter, so prefer to keep those feet dry!
General care tips can be found here