I presume you mean the herbaceous types? All I do is eventually cut off all the top growth and leave them to it. Not lost one to the cold ever. Best dead head the S. telephium types though, otherwise you get seedlings all over the place, or at least I do.

thanks for that

I do nothing whatsoever and they come back!!

cheers,,,,,,i.ll dead head some ,leave the rest,one of them will no doubt work or both thanks

thankyou for that,,i cant believe how many butterflies and bees it attracts,,,,,,,,,