I would think until we get a frost. As you know mine are still going great guns
That's one heck of a stonking photo!The flowers will keep coming till a frost does for them. Long may they last - LOVE cosmos !
If you have loads of buds, maybe keep an eye on the weather forecast and if a frost is imminent, cut some stems to bring indoors to safety.
That's a good idea. Thanks.
Oh sorry - just noticed Maggie's already answered.