How to Keep Fall Mums Blooming Longer: Expert Care and Pruning Tips

Are your chrysanthemums starting to lose their pop? Read on for what gardening experts say about how to encourage these fall favorites to stick around a bit longer, as well as tips to care for them throughout the year.

How to Best Care for Fall Mums

Chrysanthemums, also known as mums, are one of the most popular flowers this time of year. The hearty blooms are distinguished by their classic fall colors and a sweet and spicy scent that exemplify the beauty of the season. Because they can withstand cooler temperatures, they make a good transition flower for the fall months. Mums generally begin to bloom in late July, lasting through October.

While mums are resilient flowers, you can encourage them to bloom even longer with proper care. According to Amber Noyes, horticulturist, ecologist, and executive editor at GardeningChores.com, “Most mums are now grown in greenhouses because they’re ‘picky’ with lighting conditions." Noyes tells gardeners, "If you grow them outdoors, they need full sunlight, which is at least 6 hours of bright light a day on average.”

Indoor mums thrive with bright but indirect light, according to Noyes. She explains that “Mums are also photoperiodic, which means that they blossom only when the hours of light are just right. In fact, they will bloom in autumn or fall, because they will flower when they have 16 hours of darkness and 8 hours of daylight, which are the optimal conditions.”

When it comes to soil, mums fare the best with well-drained clay, sand, or loam-based soil when planted inside. Noyes notes that outdoor mums do best with a "potting mix of 1:3 good quality potting soil, 1:3 coarse sand or other draining material, and 1:3 peat moss or coco coir."

Mums should be watered once per day, ideally in the evening hours. Watering too early in the day will not allow the blooms to soak up the moisture before the sun sucks it all up. In general, mums in containers need about 1 inch of water per week.

Noyes details that mums are cold hardy when planted in USDA gardening zones 5 to 9. Mums grown indoors will do the best with temperatures between 62 and 72 degrees.

“Mums also like humidity, and ideally, it should be between 70% and 90%, which is easy to obtain in a greenhouse, but less so indoors,” Noyes explains. She adds, “So, if you grow and care for mums at home, aim for 40% to 50%; anything under this will cause them to suffer. The humidity level will also affect their mass and growth, and consequently, their blooms.”

There is no shortage of mum varieties. Some of the most popular kinds of mums include the quill, spider, anemone, pompon, and reflex.

Pruning and Propagating Tips

Most mums need to be pruned several times in order to produce large blossoms. Noyes said the first prune should happen around the end of May. Gardeners typically cut the plants down about 2 to 3 inches at this time. The shoots will continue to grow, necessitating regular pruning until about the middle of July. At this time, Noyes said that "you need to stop because your mums will be producing buds, and lots of them.”

Once the mum has blossomed, it is time to be more aggressive in the pruning. Cut the plant down completely to nearly ground level once the leaves turn yellow and begin to dry up.

Noyes recommends propagating garden mums during the spring season. These mums can be propagated using seeds, cuttings, or through division. Most gardeners decide to grow mums from seedlings. These should be planted in containers after the last frost of the season.

Dividing mum plants is another way to propagate your blooms. Simply remove the mum from its container and cut the roots into sections. Each section needs to have viable roots before you replant them into a garden or containers.

Protecting Mums During the Winter

While mums are cold hardy, they are still vulnerable to the coldest temperatures of winter. You can help them survive the elements by spreading a layer of mulch or straw around the base of the plant before the first hard freeze.

Mums in pots should be buried in the ground and covered with mulch. You may also consider bringing them indoors for extra protection.

If you want your mums to become perennials, you will also want to take steps to protect them from pests and diseases. This is especially important during times of wet and damp weather.

Savvy gardeners learn to identify the most common pests and types of diseases. For instance, some aphids are attracted to mums, sucking on the young buds and threatening the blooms. Spraying garlic water on the flowers will help to get rid of these pesky aphids.

Mums are also prone to fungal infections. This typically presents as powdery mildew. The best way to rid the mums of fungal infections is to spray a mixture of 1:10 neem oil and water and wipe the leaves with a dry paper towel.

A quick spritz of vegetable oil can be used to keep leaf miners in check. These larvae of various insect species are attracted to the inside of mums.

Mites feeding on the leaves of a mum plant can be controlled with a 1:1 mixture of alcohol and water. Be sure to wipe the leaves down after spraying this mixture so that the moisture does not harbor more pests.

With a little work, you can not only keep your mums bright and beautiful for longer into the season, but you can also encourage their growth again in the spring.

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