Q. Why do mums that I add to my garden in the fall, fair to survive our winters?
A. The difficulty you are experiencing is because the plants have spent the summer growing in containers and thus have a compact root ball. While the plants can be transplanted into the soil without setback, there is not enough time for the roots to spread out into the surrounding soil. As a result, winter freezing, heaving and drying frequently lead to the plant's death. That's why mums purchased in the fall are usually considered annual used for seasonal spots of color.
Your best chance with a potted hardy mum purchased in the fall is to plant it in the ground, mulch and water it well, and cut it back to 3 inches after the blooms are spent. After the ground freezes, cover with evergreen branches. In order to help increase the chance the container plants get rooted into the garden, slightly loosen up the root system by cutting down the sides of the root ball, thus increasing the plants ability to grow out into the surrounding soil.
Next year, you may wish to add some chrysanthemums to your garden in the spring so they have more time to establish.
• Provided by Mary Boldan, University of Illinois Extension Master Gardener. Send questions to Ask a Master Gardener, c/o Friendship Park Conservatory, 395 W. Algonquin Road, Des Plaines, IL 60016, or via email to firstname.lastname@example.org. The Friendship Park Conservatory Master Gardener Answer Desk is available 9 a.m. to noon Monday, Wednesday and Friday and noon to 3 p.m. Saturday; call (847) 298-3502.