Mums ARE better protected in the ground than in the pot. In the bedroom they will be in a warmer place than outside (even though the bedroom isn't heated) and they will have some light, which might trigger them coming out of dormancy early and becoming leggy.
My best luck has been to plant them close to the foundation on the warmest side (southeast) of the house, leaving all the foliage on so it will catch any snow. Planting this late in the season could lead to frost-heaving of the root ball. After the ground freezes, I put the boughs of the Christmas tree over the mums and this helps them stay solidly in the ground. Then, I move them to their permanent locations in spring. Best guess on my success rate is about 50% with better luck in milder winters. It's worth a try, rather than throwing them in the composter. Remember, too, that some varieties just aren't as hardy as others.
EDIT: forgot to say that in the spring, if they survive, they need to be divided, replanted and fertilized. As another posted said, after being forced into fall bloom, the plants are somewhat exhausted and division is their best chance of starting life anew.
Last edited by A Closet Canuck
on Wed Sep 14, 2016 5:50 pm, edited 1 time in total.