Garden mums (Chrysanthemum spp.) are herbaceous perennials in the daisy family and are stalwarts of the flowering autumn garden. Their hardiness and the fact that they can be pinched back during the summer so they won't bloom until fall, make these jewel-toned beauties a welcome splash in the garden at a time when most summer flowers have faded. These plants grow fast, and should bloom in the first growing season. Bloom times vary with variety and climate from early September through mid-October.
|Common Name||Garden mum, garden chrysanthemum, hardy chrysanthemum, hardy mum, mum|
|Botanical Name||Chrysanthemum spp.|
|Plant Type||Herbaceous, perennial|
|Mature Size||4 to 36 in. tall and 12 to 36 in. wide (size varies depending on the variety)|
|Sun Exposure||Full sun|
|Soil Type||Moist, well-drained|
|Soil pH||Neutral to acidic (6.5 to 6.7)|
|Bloom Time||Summer, fall|
|Bloom Color||Red, Pink, Orange, Yellow, Green, Purple, Maroon, Bronze, White|
|USDA Hardiness Zone||5 to 9|
|Native Area||Asia, Europe|
|Toxicity||Toxic to dogs, cats, horses|
Hardy Chrysanthemum Care
Plant mums as soon as the soil warms in the spring. From late spring to mid-July, shear back the plant to make the it bushier and delay flowering until the fall. For optimal blooming, the plants should be fertilized regularly throughout the growing season. After the blooms fade, cut the plants down to about six inches, and cover them with straw or another dry mulch to protect the roots over winter. Established plants should be lifted and divided every two to three years.
Mums can make a wonderful impact in containers. But when planted in mixed borders, they will end your garden season with a bang. That's especially true when you pair them with other late-season bloomers, such as sedum, goldenrod, Russian sage, asters, and gaillardia.
Furthermore, because mums flower so late in the season, they are nondescript, though not unattractive, in the garden until blooming time. Thus, they are best planted next to early bloomers. As the spring flowers die back, the mums will fill in and hide their unattractive fading foliage.
Mums thrive in full sun but can handle a bit of shade. Generally, flowering will be most profuse if they are grown in full sun. However, in warm climates, the plants often appreciate some shade during the heat of the afternoon. Mums set buds in response to day length, so avoid confusing them by planting where they might be exposed to bright nighttime light from a patio or window or even a streetlight.
These plants tolerate several soil types, but they do best in rich well-drained soil. Poor soil drainage will cause the plants to rot. They like a soil pH of about 6.5 to 6.7, slightly acidic.
Mums require a lot of water. Give them one inch per week during the early growing season, and then increase this to two or three times a week as the flower buds mature and the flowers begin to open.
When growing them in a pot, water the soil surface until moisture begins to drain from the bottom of the pot (make sure the pot has drainage holes). Water should drain freely through the soil and out the bottom of the pot. Soil should remain moist, but not soggy. Soggy soil can cause root rot and other diseases.
Temperature and Humidity
Mums do best in moderate climate conditions. Extreme heat can cause the plants to struggle. And cold regions with a hard winter freeze can see the plants succumb to cold unless they are covered with a deep layer of mulch. Mums prefer some humidity, but if the humidity is high, make sure they have good air circulation to prevent rot or disease.
For fall-planted mums to have a better chance of survival in cold areas, you need to give the plant roots and crown extra protection. First, leave the foliage on the plants until spring. Do not prune them back after frost has turned them brown. Then, either mulch the plants heavily with at least four to six inches of mulch or dig up a pot, and move the plants to a more protected spot in the garden for the winter. If you choose to move the plants, do so before the first hard freeze.
In warmer climates, consider heat delay. High temperatures, particularly at nighttime, can cause the plant to flower later than it usually would. Heat delay can cause irregularly-formed flower buds, erratic flowering, a deformed plant crown, and other developmental issues. To bypass this problem in hotter climates, look for cultivars with higher heat tolerance.
It is crucial to provide nitrogen and potassium to chrysanthemums during their vegetative phase. Feed the plants before flower buds form to promote healthy roots, bud development, and a vigorous plant. Start a feeding cycle in March, April, or May, depending upon your zone. You can get a time-released fertilizer (12-6-6), which feeds the plants for about three months. With a time-released fertilizer, you might only need to feed the plants once. The general rule of thumb is to begin feeding after all danger of frost has passed. That way any new growth resulting from the nutrients will not be in danger of damage from icy weather. Established plants should not be fed after July, so that new growth is not injured by frost.
Types of Hardy Chrysanthemums
Many varieties of garden mums have been bred. The original species are often unclear, but horticulturalists generally categorize garden mums by flower shape. Here are just a few of the classifications:
- Anemone: One or more rows of petals with a cushion-like center
- Pompom: Familiar globular shape
- Regular incurve: Petals curve up and in, forming a sphere
- Single or daisy: Looks like its cousin, the daisy
- Spider: Long, curled petals droop down and give a spider-like look
Shorter, mounding varieties of mums are generally known as cushion mums.
You will rarely find named mum cultivars in garden centers. To obtain the exceptional varieties or exhibition mums, you will need to start them from seed or order them from a nursery or specialty mail-order company.
- ‘Clara Curtis’ is a long-lasting variety that blooms relatively early in the season with single or semi-double daisy-like pink flowers.
- ‘Mary Stoker’ is an early-season mum with single pale yellow flowers.
- ‘Apricot Moneymaker’ is a mid-season, anemone-style mum with pale apricot-yellow blooms.
- ‘Ruby Mound’ offers an early-season bloom with large double, ruby-red flowers
- ‘Patriot’ is a mid- to late-season bloomer with pure white pompom-shape flowers.
- 'Tripoli’ blooms very late in the season and has daisy-like purple flowers with yellow centers.
Pruning Hardy Chrysanthemums
Pinching chrysanthemums promotes bushy plants, delays bloom time until later in the season, and increases the number of buds and blooms. When the mums are six to eight inches tall, pinch back the center leaves with your fingertips to remove the tiny new leaves and boost new growth. Pinch again every time the plant grows another six inches. If you have a September-blooming variety, stop pruning at the end of June; for October-blooming mums, stop near the end of July. Never prune away buds.
After frost kills the foliage, prune the plant back to just above the soil, using a sturdy pair of pruning shears. Cover the remainder of the plant with several inches of mulch for protection during the winter.
Propagating Hardy Chrysanthemums
You can propagate mums in several ways: by division, seeds, and cuttings. The most straightforward and fastest method is through division.
- Division: Divide plants that have grown in the garden for at least two years. Younger plants will not have a sufficient root system to survive. By every third spring, divide chrysanthemums to rejuvenate them. Do this in the spring. Divide when plants are at least 6 inches tall. Be careful not to damage the roots. Replant at least 18 inches apart.
- Cuttings: This is an excellent method to create a replica of the plant you have. It does away with the mystery that comes with seeds. Cut a stem that is at least four inches long, dip the cut end into a rooting hormone, plant it in a container filled with potting soil, wait about four weeks or so for foots to form and for the plant to grow another two inches, then transplant it outside.
How to Grow Hardy Chrysanthemums From Seed
Mums can grow from seeds, but it is best if you use purchased seeds. If you attempt to plant seeds from your own plants (most are hybrids), the resulting plant might not be true to the parent. If you are OK with a mystery result, then go for it. Start seeds indoors six to eight weeks before your last frost date, and harden off the plants before transplanting outdoors.
Potting and Repotting Hardy Chrysanthemums
Repotting is the single most important thing you can do to increase the longevity of your mums. Most mums are completely root-bound when you purchase them. The roots have consumed the entire pot, which makes it hard for the soil to retain any water. To repot, choose a container that is a little bigger than the last container. Fill the bottom of the new pot with good-quality potting soil. Detangle any roots you can, but do not damage them.
When you place the plant in the new pot, the surface of the soil should be one inch below the lip of the new pot. Make sure the roots have good contact with the soil. Tamp down the soil gently. Water the plant until water flows out of the bottom of the pot.
Overwintering Hardy Chrysanthemums
Planting mums in the garden in late summer or early fall does not guarantee sufficient time for the plants to become established. This is not a problem in warmer climates, where a bit of deadheading will satisfy most mums after bloom, but in areas with sub-zero winters, perennial plants need strong roots to anchor them into the ground. The repeated freezing and thawing of the soil can heave the plant out of the ground and kill it
If you do have an established plant, prune it back to just above the soil when the foliage dies off after the first frost. Cover it with several inches of mulch to help it survive the winter.
Mums can suffer damage from aphids, thrips, and spider mites. Some signs include leaf and stem damage, webbing on the plants, and visible insects. Earwigs and leaf miners can also be troublesome issues; solve this with a blast of water or an insecticidal soap spray. Pick off any slugs and snails by hand.
How to Get Hardy Chrysanthemum to Bloom
In most cases, mums purchased from a nursery or garden center are purchased right before or as they are blooming and can be left in their container to create colorful garden scenes for several weeks. Though most mums will bloom in September, October, or even a bit later, some will bloom earlier, especially in climates with very cool nights in spring and summer.
To ensure your mums bloom profusely, take care to prune them when the stems are only six to eight inches in length. Regular pruning until buds appear is the best way to ensure healthy blooms. After the plant blooms, deadhead the flowers regularly to open up any "hidden" bulbs to sunlight and encourage a longer flowering period.
Common Problems with Hardy Chrysanthemum
In most cases, mums in containers brighten up the fall with a vivid burst of color and die back with the first frost never experiencing any problems. However, those who choose to plant mums in the ground and keep them healthy for years might see the following issues:
- Fungal problems. Mums are at their best in the fall, when the weather is cooler and wetter than usual. That moist atmosphere is an invitation to mold spores and fungal problems. Anti-fungal sprays can help remedy the problem, as can removing infected stems.
- Diseases. Common diseases include botrytis, leaf spots, rust, powdery mildew, stem and root rots, verticillium wilt, aster yellows, and viruses. If your plant has visible damage or just seems to be failing to thrive, a disease might be the culprit. Leaf spots and powdery mildew are rarely fatal, but plants with other diseases should be removed and destroyed.
- Viruses. Some viruses are transmitted by insects, such as chrysanthemum smut. Stunted growth and yellowed, brown, or dropping foliage are tell-tale signs. Unfortunately, there are few cures for this, and might require destroying the plant to prevent it from infecting others.
How long can hardy chrysanthemum live?
Those grown in containers will usually only last for one season. Those planted in the soil in USDA cold hardiness zones 5 through 9 can often survive for three or four years before dying back for good.
Can hardy chrysanthemums grow indoors?
Yes! However, keep in mind that mums in containers designed to grow indoors are not usually the hardy variety that is meant to grow outdoors. When purchasing mums, choosing those that are meant for indoor growth might make your life much easier.
Where should I place hardy chrysanthemum in my house?
Keep the mums in a well-lit room but ensure they don't receive light during the night; even a streetlight outside can be enough to confuse the plant and throw off the blooming schedule. Ensure the plant has good air circulation and not too much humidity.