How to Grow Hardy Mum (Chrysanthemum morifolium) Plant

Yellow mums as a backdrop to ornamental kale
David Beaulieu

Chrysanthemum flowers such as mums have traditionally been boiled in China to make a tea and used in folk medicine for influenza patients. In landscaping, chrysanthemums are valued for the fact that they bloom in fall, helping you to achieve four-season interest in your yard. They look best planted in a mass (but for plant health, do not overcrowd). Chrysanthemum flowers are also a favorite of florists for arrangements, due to the longevity of their blooms.

Hardy mums (Chrysanthemum morifolium) not only come in many different colors, but they also have different flower forms and growth habits. For instance, the popular "cushion" type has a compact growth habit. The shape and arrangement of the petals of a mum's blooms can also vary from group to group. The most popular flower form is the "decorative," which is so packed with long, broad petals that you can hardly see the center. Along with such diversity, the plants' late-blooming period makes them a must-have in the Northern fall gardens.

Hardy mums can be treated as an annual even though it is technically a perennial. If you're just looking for a pop of color in your late-season garden, buy a plant already in bloom. But, if you want to nurture the plant year after year, buy seeds to plant in early spring or in the fall at least six weeks before the first hard freeze in your zone. Fast-growing, mums will reach their full height of about two feet within the first year, with the plant filling out a little more each year after.

Botanical Name Chrysanthemum morifolium
Common Name Hardy mums, garden mums
Plant Type Herbaceous perennial
Mature Size About 2 feet high
Sun Exposure Full sun
Soil Type Well-drained, evenly moist, and rich
Soil pH Slightly acidic to neutral
Bloom Time Late-summer or fall
Flower Color Gold, yellow, bronze (rust), red, burgundy, pink, lavender, purple, off-white, and white
Hardiness Zones 3 to 9 (USDA)
Native Area Asia and northeastern Europe
Toxicity Toxic to animals

Hardy Mum Care

Growing these plants for optimal display value requires getting a few things right. They are fussier to grow than many other plants. Note that there are cultivars considered "hardy mums" and cultivars considered "florist mums." Hardy mums put out stolons. Florist mums put out few or no stolons and are less likely to over-winter in cold regions.

Since it is so important to know which cultivar you will be working with, it is wiser to buy mail-order hardy mums (single-stemmed rooted cuttings) from a catalog in spring rather than buying already-blooming potted mums in the fall. In a good catalog, you have all of the relevant information in front of you, including which types are the hardiest. An example of a nursery series that is hardy is 'mammoth'.

Another benefit of buying from a catalog is that you can plant your mums in spring. Spring planting gives the plants longer to become established, thereby improving their chances of surviving the winter. Choose a location where they will be sheltered from winter winds.

Once you have selected chrysanthemum flowers suitable for your area and planted them, you have to care for them properly. Do not overcrowd chrysanthemums: Good air circulation reduces the chance of disease.

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Watch Now: Everything to Know About Growing the Hardy Mum Plant

Light

Grow hardy mums in full sun in the north. In the south, however, they can profit from being grown in light shade. Chrysanthemum flowers are "photoperiodic": They bloom in response to the shorter days and longer nights experienced (in the northern hemisphere) in fall. Therefore, do not plant chrysanthemum flowers near street lights or night lights: The artificial lighting may wreak havoc with their cycle.

Soil

In the north, it is critical to provide mums that you wish to grow as perennials in well-drained soil. This is because it is not just cold temperatures that can kill mums in winter but also poor drainage.

Water

During the growing season, check to ensure that the soil throughout the root zone is evenly moist.

Temperature and Humidity

As long as plants are established before winter, hardy mums do well in areas with hard winters. For areas with milder winters, like the southern half of the United States, care needs to be taken to protect plants from the harsh summer heat.

Fertilizer

Fertilize in spring with a slow-release fertilizer. The NPK value of the fertilizer should be 12-6-6. The benefit of using a slow-release fertilizer is that you only have to fertilize once per year. If you use a fertilizer that is not slow-release, you will have to fertilize multiple times each year, as follows:

  • Fertilize your hardy mums once each month in spring from the time that they first come up.
  • In summer, fertilize once in July.
  • Do not fertilize after July. Any new growth put on after July would be too late to harden off for winter.

Are Hardy Mums Toxic?

All parts of the mum are harmful if ingested by dogs, cats, or horses, especially the flower heads. The plant can cause skin irritation in humans but isn't lethal for humans or animals.

Symptoms of Poisoning

In pets such as cats and dogs, as well as in horses, symptoms include vomiting, dermatitis, increased salivation, diarrhea, and lack of coordination, according to the ASPCA. Contact a veterinarian if these symptoms appear.

Hardy Mum Varieties

There are several different categories of mums, each with particular characteristics and varieties of its own.

  • Anemone: Featuring long, flat petals, the blooms on this type of mum reaches a max size of about four inches. Varieties include light-purple ‘Dorothy Mechen’ and ‘Adrienne Mechen’, which have flowers with a pink center that fades to bright white tips.
  • Pom pom: These fluffy mums are also known as button mums. All varieties produce compact blooms, just in different colors. Some common varieties include 'Patriot', 'Garnet', ‘Tinkerbell’, and ‘West Point’.
  • Spoon: Named for its spoon-shaped petals, this type of mum grows petite flowers of just four inches in diameter. Popular varieties include 'Kimie', featuring yellow-gold petals, and 'Matchsticks', which have yellow centers that end dramatically in bright red "spoons."

Pruning Mums

Do not prune the plants in the fall. Existing branches offer protection for the roots. By every third spring, divide chrysanthemums to rejuvenate them. Hardy mums will be even hardier with winter protection. Mulch them for winter. If you can't locate them where they will be sheltered from winter winds, then you should build a modified version of the shrub shelters used for winter protection for shrubs.

Pinching hardy mums (emoving the tips of new growth, thereby stimulating the plants to send out side-shoots) requires more maintenance than any other aspect of caring for them. Pinching yields compact, bushy plants with more blooms. It is called this because, on non-woody plants, you can generally accomplish the task simply by grasping the stem (at the targeted spot) between thumb and forefinger and severing it with a pinching action.

Start pinching in the spring when the new growth has reached 4 to 6 inches in length. After that, every two to three weeks, pinch the center out of any more growth when it reaches 6 inches. But stop pinching chrysanthemums around the beginning of summer, or else bud formation will not occur soon enough to ensure flowering for fall.

You also have to be ever-mindful that, while chrysanthemum flowers hold up against light frosts, hard frosts will damage the blooms that you have worked so hard to produce. Your pinching activities, then, must be balanced with the fact that you are in a race against time to get blooms before fall's first hard frost: That is why it is so important to stop pinching at the right time, based on the cultivar you have. Stop pinching:

  • Early-blooming cultivars by mid-June
  • Cultivars that bloom in September by late June
  • Cultivars that bloom in October by July 4
Article Sources
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  1. Chrysanthemums. University of Minnesota Extension Website