Good question! I also am wondering if its time to pull my potted zinnia (I've got about 8 large pots of them). They are still putting out buds but the lower foliage is so beat up at this point they are not very pretty to look at. Same with the petunias in the window box. Still blooming but looking worse for wear. It has been soooo cold and rainy here as well which has not helped. I dont think my balcony saw sun for 3 days! Looking forward to hearing suggestions.

the issue is winter heave ... unlike trees/conifers/shrubs ... perennials need to get into the ground.. so they can GRAB HOLD .... before ground freeze ... its really a matter of day temps versus night.. for odds of success ... do not transplant if 100 degree days and 75 degrees nights.. just too much stress... but if night temps are getting into the 50 or 60's .. then then can recover from whatever the day temps are ... its all about getting some roots to grow .. to hold on.. a good blanket of mulch really helps .... I NEVER FERTILIZE IN MY Z5 AFTER ABOUT 8/15 ... we do NOT want lush vegetative ... GREEN .. growth late in fall.. we want the plant to harden off properly .. so dont get some bright idea that you can HELP your transplants with a heavy dose of fertilizer ... ken

Pippi, in my zone, we can sow the seeds in the fall when we pull the summer blooming annuals. Disturbing the soil gives the new seeds a place to rest and germinate. I sowed mine in October, but others can sow earlier. I've had poppy and larkspur last through the winter this year, even with temperatures in the low teens for many nights and never breaking the freezing mark during the day for a week. Our first hard frost this past fall was Dec 5. So, about two months before your first frost would give you plants that should survive in your zone. This may vary with more northern zones. I also mulch with shredded leaves for the winter, only pulling them off the beds once the nighttime temps are back into the upper 20s. Rudbeckia was self sown in the perennial bed. They've stayed small until now, as they're starting to put out new growth. By small, I mean about 2" across with several sets of leaves. I scattered seeds all summer long too. And now, I've got seedlings popping up all over the place in those areas.

Yes, the lack of sun past August will decrease your fall bloom. Unless your fall flush occurs in August anyway. Here, fall bloom starts in September, from buds that formed at the very end of August at the earliest. I have a friend with roses in the same kind of situation you describe, and she gets no fall blooms. Here there is no such thing as a shade tolerant rose. We do not get enough sun for any rose to do well with less than full sun. You do not say where you are so I can't judge what kind of climate you're in, except northern latitude judging from zone 4! But - a cloudy north, or a sunny north? We're a very cloudy north. You may not be. But go ahead and experiment! All we can do is tell you what we think might happen. We puny humans are often wrong when it comes to guessing what Mother Nature will do.