Garden Variety: Can mums survive the winter? It depends on planting, care

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Whether chrysanthemums survive the winter depends in large part on when they were planted and how they’re cared for.

Chrysanthemums, often called mums for short, are the most popular flower for fall color in the landscape in the Midwest. They adorn porches, planters and gardens with their varied hues of gold, orange, pink, red and white and are often paired with other fall favorites such as pumpkins, corn stalks and straw bales.

But despite their commonality, one big question lingers about mums: Are they annual or perennial in Kansas?

The simple answer to the debate about mums’ hardiness is that their survival really depends on planting and care. However, even the best gardeners might have difficulty getting them through the winter.

For best success with survival, get them in the ground early in the season (think Labor Day), break the roots up at planting and water frequently. After blooms fade in late fall, cut plants back to 2 or 3 inches tall. Apply a layer of mulch over the top for added frost protection and to reduce soil moisture fluctuations. Continue to water plants throughout the winter during extended dry periods when temperatures are above freezing.

Mums that are planted later in the season may still survive if the other practices are followed. This includes plants that are still in their nursery pots right now. The key with these plants, especially with the dry weather the Lawrence area has been experiencing, is watering. For plants in pots, transplant them into the ground when they are finished blooming, as they have a much greater chance of survival there than left in the pot.

The other option is to forget about trying to overwinter mums and think of them as annual flowers. Like spring- and summer-flowering annuals, mums provide a lot of color for an extended period. They are relatively inexpensive for the size of plant and quality of display. They can be composted at the end of the season and replaced with a different color or flower type next season.

Another consideration when deciding whether to try to keep mums alive this winter or compost them at the end of the season is to think about their care in future seasons. They will not bear the abundant blooms with which they were purchased without extra care next spring and summer. They will bloom on their own, but the blooms will start mid-summer and be sporadic on the plant and through the rest of the season.

To get overwintered mums to bloom evenly and delay the start of blooms to the fall season, plants need to be cut back or pinched. Depending on the size of the plants, this work might be done by hand or with hedge clippers. Clip plants when they are about 6 inches tall, and repeat the process each time the stems have grown about 6 inches. Continue cutting mums back as needed until the first part of July. Then they should bloom evenly in the fall.

Overwintered mums will also benefit from fertilizer applied in the spring when new growth begins. Make a second application in mid- to late July.

If mums are hardy, why do so many gardeners have difficulty getting the plants to survive? The answer to this one takes a little understanding of plant growth and consumer habits.

First, hardiness is based on a plant’s ability to survive cold temperatures. USDA hardiness zones are based on average annual minimum winter temperatures. Garden mums (almost all the varieties sold at garden centers) are hardy to zones 4 and 5. Lawrence is in zone 6, meaning that winters in this area are milder than what the plants are capable of surviving.

Survival is most likely when plants have adequate root systems and are established in their planting site before freezing temperatures arrive. But mums are typically purchased and planted in the fall when they are full of blooms, and when plants are blooming, they are putting energy into their flowers instead of their roots.

Mums would have a better chance of survival planted in the spring or early in the fall before they start blooming, but a green plant is a hard sell, and mums are far from most gardeners’ minds in the spring.

Another thing to remember is that plants get watered every day or even multiple times per day in a greenhouse or garden center. Mums are susceptible to root rot diseases, so they are potted in lightweight potting mix that dries out quickly. To keep them alive and healthy in a garden, you need to water them regularly unless their roots can expand into additional soil. Many fall and winter mum deaths are probably due to plant or root desiccation.

There are a few varieties of mums that are truly annual. These are most common in the floral industry and not likely to be found at garden centers. However, hardy mums may be labeled as annuals in error, because of nationwide markets or because the garden center doesn’t want to make any promises.

— Jennifer Smith works in regulatory horticulture and has worked as a horticulturist for various government entities. She has experience in landscape design and maintenance and as an educator.


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