Answer: It really may not be anything to do with your gardening ability. Fall planted mums are at a disadvantage because they have so little time to become rooted prior to the cold weather. Also, many of those sold in the fall are not necessarily winter hardy varieties. Too, in order to survive the winter they must be planted in a spot that is very well drained, otherwise they will rot during the winter. IF you want hardy mums, it is better to plant them in the spring. If you can't find any locally, you can try to find a gardening friend who has some and will share a division or two, or you can try mail order. Bluestone perennials for example sells hardy mums in the spring.
For success, they must be planted in a spot with full sun all day long, rich soil that is evenly moist yet well drained (not saturated or sopping wet), and they must be kept watered and mulched all summer. You will also need to pinch them regularly to induce branching for a nice dense plant; this also delays blooming until fall and yields the most flowers. Pinch off the growing tips every other week or so until the middle of July, then allow the buds to develop.
In fall after the flowers fade you can trim the stems off if you wish but leave at least six inches intact to help protect the crown during the winter. Mulch between but not over top of the plants. In spring, trim them off as short as possible but be careful not to damage the new growth coming up at the perimeter of the plant. Take root divisions from the vigorous new portion of the plant; a piece several inches across will make a nice plant by fall. You can also root tip cuttings. Discard the old center as it will not be as vigorous as the new divisions.
I am not sure which yellow you have in mind -- there are hundreds or maybe thousands of different mums -- but I am sure you can find some hardy mums you like. Your zip code places you in zone 6A, the coldest part of zone 6. Depending on your microclimate it might actually be as cold as zone 5. So look for varieties rated winter hardy to zone 5. I hope this helps.
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