I love gladiolas and have grown them in containers here in the past. My problem nowadays is that I have just about run out of room to put any tall growers as I have shrubs that are taking up space now in the best sun.

Based on my experiences the past 2 years, they usually start migrating around August - September. This is my first year with a mature male (who was a juvie last year), so I will watch closely for when he leaves as they are usually the first to arrive in spring and first to go in late summer. The juveniles and females are usually the last to leave and last year, my last sighting was September 11. However many have reported some still hanging around in October, including the late migrators coming down from further north, so it's usually recommended to keep the feeders going at least until then.