Answer: If it's just the flowers that are wilting, they may have "gone by" and are ready to be trimmed off. If the entire plant is wilting, it may be due to transplant shock. A little wilting can be expected after transplanting, especially if the weather has been sunny or windy. If you transplanted your mums more than a week ago, then they may not rebound. After frost kills back the tops, trim them off fairly short, water them one last time, and perhaps they'll return next spring.
All newly planted mums require careful attention to soil preparation and watering or they may wilt. This is especially true with those that are very potbound when purchased. In some cases they are used to daily watering at the growers and it is difficult for them to adjust to growing under garden conditions. For these reasons some people consider mums to be the equivalent of cut flowers -- a pretty but ephemeral decoration. If you are planning to grow them as perennials your best bet is to purchase them as early in the season as possible (spring is best if you can find them) so they can become well established before undergoing the stresses of blooming and winter weather.
The best insurance for mums is that you plant them early enough that they have time to get well rooted in a sunny spot with well-drained soil before the ground freezes. Opinions vary, but in my experience mums winter better without any mulch over the crowns, since the most common danger is rot. A good snow cover makes an admirable insulating layer but if you prefer to mulch, use something very light such as pine boughs. Next spring you should find new shoots emerging around the perimeter of the plant -- although it is also worth keeping in mind that some mum varieties are simply hardier than others. I hope this helps!
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