Answer: There are two big risks to keeping the mums in terra cotta pots. One is that the terra cotta pots will freeze and crack or shatter. The second is that the plants' roots will freeze and this will kill the plants. That is why it is better to plant them in the ground where the roots will be insulated from the cold. Planting them late in the fall however, increases the risk that they will not winter successfully because they have not had time to become established in their new location before the cold weather hits. Sometimes it is better to just consider them as seasonal decorations.
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