I think you can up until about 30 days before your first frost day. You don't want trying to put on a lot of growth durning your cold weather. We have very little cold here so I can normally push mine all winter, last year was the expection, our coldest in 80 years. Still seen about 75% first year bloom. This was taken Oct 1 two years ago All those seedlings are now gone and I'm useing those beds for the babies this year.
