Chrysanthemums, more familiarly known as mums, are sturdy perennial bloomers that will often survive cold winters with a bit of extra care and attention and a cover of protective mulch. Plant chrysanthemum varieties bred for winter hardiness if you live in a northern climate with extra-cold winters, as some chrysanthemums, such as florist chrysanthemums, are more sensitive and may not tolerate extreme cold.
Care for your mums throughout the season, as vigorous, healthy mums are better able to tolerate cold weather. Spring-planted chrysanthemums have a better chance of surviving the winter as the roots are well established by the time temperatures drop in late autumn. Mums planted in late summer or early autumn may not survive the winter in cold climates.
Soil quality is critical for winter survival, as mums planted in poorly-drained soil are more susceptible to freeze and root damage during cold weather. Mums planted in well-drained soil won't be standing in muddy, cold soil. Use a rake to level the soil before the weather turns cold, as any dip or hollow allows standing water that may damage the roots.
Place 4 to 6 inches of mulch over the chrysanthemum after the ground freezes in early winter. Use an organic mulch, such as chipped bark, pine needles or dry, chopped leaves. Avoid unchopped leaves, as wet, soggy leaves become heavy and compacted, preventing air circulation to the roots. Check the plants regularly and replenish mulch that blows away or decomposes. A few pine or free branches laid over the ;plant helps to keep the mulch in place. Don't cut the mums down in autumn, as the dry growth helps protect the plant, and helps keep mulch in place.
Spring is the best time to cut off dead growth. Cut the mums down to within 3 to 4 inches of the ground. Remove winter mulch in early spring, as allowing the mulch to remain over the mums may inhibit growth. Rake the mulch to the side of your flower bed until you're sure all danger of freeze has passed. If cold weather is predicted, rake the mulch over the plant.
If you're concerned that your mum may not survive the winter, pot it up in a container filled with commercial potting soil. Bring the mum indoors until spring. Place the mum in a sunny window. Water lightly, providing just enough moisture to keep the soil from becoming completely dry. Pinch the tips of the mums to keep the plants neat and well-shaped. Move the mum back outdoors after frost danger has passed in spring.