I love to overwinter mums, but one has to remember that the growers can take any mum cutting, fertilise it, use black cloths or other light blocks to regulate its day length, and use growth regulator to produce squat, brittle cupcake. They are not your grandmother's mums. Those in my mother's garden were three feet high and bloomed in late October or even November!
One year my brother, a notorious saver, took me out for a ride to pick up discarded mums. We got thirteen!
Well, some of them are still going strong, but though I pinch them back right up until Jul 4 (Zone 6) by now those that weren't decimated by Japanese beetles are --you guessed it--three feet tall. I have a lovely pale pink single that I am going to increase by cuttings next year--I hope--because I love the look of the old-fsahioned clumps of mums spilling out of their beds.
Hi Quiltjean, You are so right that the mums that spend the summer growing in your garden are nothing like the "cupcake" mums (good description!) available for purchase in the fall. The overwintered mums have stronger stems and in general just look more natural. I love the idea of you and your brother scavenging for discarded mums!