How can I keep my mums for next year?
Certified GKH Gardening Expert
If they are in pots, place them in a cool, dark place. Water them about once a month until spring. In early spring, resume normal watering and bring them out when the last frost has past. For those outdoors (in ground), trim to ground and mulch well. This article may also help: https://www.gardeningknowhow.com/ornamental/flowers/chrysanthemum/wintering-mums.htm
In case you're uncertain about their survival, you can also take cuttings from them. Here is more information: https://www.gardeningknowhow.com/ornamental/flowers/chrysanthemum/mum-propagation.htm