The perennial flowering plants known as spider mums are a unique, exotic form of the hybrid chrysanthemums that fill landscapes and container gardens with colorful flowers in the fall.
The term spider mum simply refers to one single exhibition class within the very large group known as garden mums or hardy mums. All garden mums are derived from Chrysanthemum x morifolium hybrids, and so-called spider mums are the subgroup that features tubular petals that are hooked or curved.
Spider mums typically have large flower heads that can grow up to six inches in width, depending on the cultivar. Like all other garden mums, they are herbaceous perennials that bloom in the fall. Thus, spider mums are grown and cared for exactly as other garden mums bred for garden use. Like other types of garden mums, spider mums are sometimes grown as potted annuals, discarded when they are finally killed by frost.
Spider mums are best planted in spring from rooted cuttings or small potted live plants, packaged and sold by online retailers—varieties grown specifically to serve as garden perennials rather than display annuals. They grow quite quickly to mature flowering plants by late summer and fall. Spider mums are relatively short-lived perennials, usually declining within a few years.
|Common Name||Spider mum, Fuji mum, autumn mum, florist's chrysanthemum, garden hardy chrysanthemum, garden mum|
|Botanical Name||Chrysanthemum x morifolium (or C. morifolium)|
|Plant Type||Herbaceous, perennial, annual|
|Mature Size||1–3 ft. tall, 1–2 ft. wide|
|Sun Exposure||Full, partial|
|Bloom Time||Summer, fall|
|Flower Color||Yellow, pink, red, white, purple, bronze, rust|
|Hardiness Zones||5–9 (USDA)|
Spider Mum Care
Not all varieties of Chrysanthemum x morflorium are suitable as garden plants. The vast majority of the potted flowering plants offered at garden centers in the fall are bred to be used as potted annuals not as perennials. Even in zones where they are hardy, these garden center plants do not return in the spring if they are planted in the garden—or if they do return the following year, the flower performance is much different.
If you want varieties suitable for perennial garden use, you will probably need to buy them as rooted cuttings or small living plants from online retailers who specialize in garden mums for landscape use. These mums are usually shipped for planting in the spring, which gives you time to perform the repeated pinching back from spring to midsummer that is required to create the huge, dramatic blossoms for which spider mums are known. Growers seeking display-quality blossoms often pinch off all but a single flower bud on each plant.
With these garden mums, give them at least ten inches of room between plants, and add a stake or grow-through support because the large blossoms will need support in a few months.
Like all garden mums, spider-type mums do best in a sunny location where they receive at least six hours of sunlight daily. Garden mums should still survive in partial shade, but expect a less impressive floral display is such locations.
The ideal soil for garden mums, including spider mums, is fertile, loose, well-drained soil that is slightly acidic (pH 5.8 to 6.5). Experienced growers routinely amend soil with peat moss and other organic amendments to keep mums happy. But the accepted pH level is relatively narrow for garden mums because soil that is too acidic can also cause nutritional problems such as yellowing leaves. If you want to be a serious grower of mums, careful control of soil pH is essential.
Garden mums appreciate daily watering during their growth period. Aim for soil that is consistently moist but is not water-logged. Ground-level soaking is better than wetting the leaves with spray irrigation, as it reduces the likelihood of fungal infections. Wet leaves can cause mildew and other fungal diseases, and mums can also be susceptible to the Septoria chrysanthemella fungi, whose spores are transferred during watering.
Even in the winter, it's a good idea to keep the soil damp as this will improve the chances of a successful hibernation period if you are growing mums as perennials.
Temperature and Humidity
With their delicate tubular petals, spider mums are a bit more cold-senstive than the general class of garden mums. Spider mums are considered reliably hardy in USDA cold hardiness zones 6 to 9, borderline hardy in zone 5, and will need to be grown as annuals (usually in pots) in colder regions.
Garden mums have shallow root systems and benefit from three or four applications of fertilizer each growing season, spaced about one month apart beginning in spring. A general-purpose balanced fertilizer, either granular or water-soluble, will be sufficient. For the amount to use, follow the product label instructions. Feeding should be withheld in late summer as the plants prepare to bloom.
Types of Spider Mums
Garden mums that fall into the true spider classification are rarely sold as potted plants in garden centers. You will probably need to buy rooted cuttings, small living plants, or seeds from an online retailer, and even those sources might offer relatively few types that are true spider mums. A few of the more notable spider mum cultivars include:
- ‘Descanso’ has huge blooms with snake-like petals in shades of bronze and apricot.
- 'Chesapeake' is a white-flowered cultivar.
- ‘Fleur de Lis’ has lilac-pink petals.
- 'Coral Reef' has very large coral-orange-gold flowers.
- 'Evening Glow' is a large, spreading plant with salmon-rose petals transitioning to bronze in the centers.
- 'Lava' has yellow petals tipped with bright red.
Newly planted garden mums should be pinched back fairly hard when they are six to eight inches tall, then several more times until about mid-August. The goal of pinching is keep the plants dense and bushy and to remove all but a few of the buds, ensuring large, dramatic flowers. In climates where garden mums are perennial, the plants should be cut back to ground level when frost kills the stems and leaves.
Propagating Spider Mums
Propagation of spider mums can be accomplished by seed, stem cuttings, and root division. Root division is the most dependable method, and experienced growers usually do this each year in the early spring:
- Use a shovel to dig up the entire root ball of the plant.
- Divide the rootball into at least four pieces, each with a healthy section of roots and growth eyes evident at the crown. If the center portion has become woody and non-productive, it can be discarded.
- Replant the plant divisions into soil heavily amended with peat moss or compost. The crown portion should be just barely covered with soil. Allow 12 to 18 inches of room between plants.
- Water thoroughly after replanting and whenever the top of the soil feels dry to the touch.
How to Grow Spider Mums From Seed
Growing garden mums from seed is tricky because the seeds are very tiny and it can take as much as four months for germinated seeds to mature into flowering plants. Results can be unpredictable, because garden mums are hybrids that readily cross-pollinate with other varieties. Any seeds you collect from a spider mum plant could well surprise you by creating plants with flowers that bear no resemblance at all to the parent plant.
If you do want to try this experiment—either from purchased seeds or seeds collected from an existing plant—it's best to start them indoors at least six weeks before the last expected frost date in your area. Plant the seeds in trays or small containers filled with damp seed-starter mix. Just barely cover the seeds, then place the containers in a very bright, warm (70 degrees Fahrenheit) location and keep the potting mix damp. Seeds typically germinate in about 10 to 15 days. Thin out the seedlings as they grow, then transplant them into individual containers when they are three to four inches tall.
Reaching flowering maturity can take as much as four months. Young plants sometimes do not flower until their second season.
Potting and Repotting Spider Mums
Container culture is a preferred method for growing garden mums, and specimens grown in a good moisture-retentive potting soil often do better than in-ground plants. Use a good-sized pot (at least 10 to 12 inches in diameter), and fill it with standard potting soil amended with extra peat moss or compost. Give the pots a sunny location, and water and feed them frequently. Potted plants often need daily water during hot summer days, and they should be fed every two weeks until mid-summer, when the flower buds begin to develop in earnest.
If you are growing potted garden mums as perennials, the pots should be moved into a sheltered location, such as an unheated garage or porch, for the winter. These plants require a winter dormant period with temperatures below 50 degrees Fahrenheit, so don't try to grow them as houseplants.
When growing potted mums as perennials, it is best to divide them annually each spring, discarding the woody central portion and planting each peripheral piece of the rootball into an individual container.
In the northern end of the hardiness range, apply a thick layer of mulch over the roots for winter, which will prevent the roots from heaving due to freeze-thaw cycles. In transitional zones where spider mums are not fully hardy, gardeners sometimes have good luck by digging up mums, planting them in containers, and moving them to a sheltered, dark location to hibernate at 32 to 50 degrees Fahrenheit for the winter. The potted plants should be well-watered immediately after transplanting but then allowed to go dormant until the soil warms in spring when they can be pruned back and transplanted back into the garden. This rather rigorous handling is possible because mums have shallow root systems that don't resent transplanting.
Common Pests & Plant Diseases
Aphids, midges, leafminers, mealybugs all can be problems with garden mums. They are best controlled by dusting the plants with pesticide powder.
High humidity and overhead spraying can make garden mums susceptible to various fungal leaf spots, powdery mildew, and rust. Spray or powder fungicides applied early can prevent the most serious diseases, but badly diseased plants should be removed and destroyed to prevent the spread of pathogens.
How to Get Spider Mums to Bloom
Spider mums typically bloom for about two weeks, usually in late September and early October, which is a little later than other types of garden mums. Good flowering is usually assured if the plants have received plenty of sunlight, regular water, and feeding up to midsummer. Feeding plants too late might compromise blooming, as the plant will continue to devote energy to green growth at the expense of flowers. Stop feeding about July 15.
For dramatic large blooms, pinch back the plants repeatedly in spring and early summer. By pinching off most of the smaller flower buds, you can force the plant into producing a few large, dramatic flowers.
Garden mums are especially sensitive to lighting conditions, and they sometimes fail to bloom if growing under certain types of artificial street lighting. These fall bloomers are prompted into blossoming by shortening daylight hours, and street lighting can confuse the plants into thinking that the time is not yet right for blooming.
Common Problems With Spider Mums
The most common issues with garden mums are due to insect damage or fungal disease, both of which are generally recognized due to symptoms evident on the leaves (see above). But you might also encounter symptoms that are not caused by fungi or insects:
Mums that develop brownish-gray scaly spots on the leaves might be suffering from excessive salts in the soil. This is often the result of too much fertilizing.
Individual Stems Turn Yellow
Fusarium wilt is a fungal disease that can cause individual branches to turn yellow and die, eventually killing the whole plant. It is more likely to occur if the soil is very acidic, so raising the pH slightly with agricultural lime might prevent the disease. Affected plant parts should be pruned off and destroyed, and a seriously diseased plant will need to be removed entirely to prevent spread to other plants.
Webs Between Leaves and Stems
Webby residue between leaves and stems on garden mums is not a symptom of insect damage, as you might expect, but rather a fungal disease known as web blight. Early application of fungicide, along with good spacing between plants or pruning to improve air circulation, often prevents the disease.
Entire Plant Is Yellow
If an entire garden mum plant is yellowish rather than dark green in color, this is usually a sign of chlorosis, a condition caused by nutritional deficiencies. In the case of garden mums, this can be caused by soil pH that is either too acidic or too alkaline. A soil test followed by necessary amendments will prevent this condition.
How should I use spider mums in the landscape?
This variety of garden mum has very unusual flowers, so plants should be positioned in the landscape where they will be highly visible and easily appreciated. Spider mums are ideal for planting in large containers on sunny decks and patios or in a cutting garden.
Why can't I transplant a potted garden mum into the garden?
You can. But the flowering potted mums sold at most garden centers are bred for vibrant display as potted annuals, and they very often have limited winter hardiness. Further, they have been carefully grown under controlled lighting, and the plants often bloom unpredictably in the following seasons. If you want to grow truly perennial garden mums, buy them from online retailers specializing in varieties bred for garden planting.
What other Chrysanthemum species make good garden plants?
Many of the common daisy-like garden species are actually Chrysanthemum species, including:
- C. coccineum (painted daisy) is a tall perennial form that grows up to 42 inches tall, available in many named cultivars. It is hardy in zones 3 to 7.
- C. x koreana (Korean mum) is a perennial species growing to four feet tall, with yellow to orange flowers. It is hardy in zones 4 to 9.
- C. x rubellum (Rubellum hybrids) are 36-inch tall plants with better shade tolerance than other types. They are hardy in zones 4 to 9.
What is the difference between "hardy" mums and "garden mums"?
These are two different names for the same type of Chrysanthemum, the group falling under the botanical name Chrysanthemum x moriflorium. Originally this type was most often called hardy mums, but because their winter hardiness is questionable in many regions, the term garden mum is now preferred.
Wyman, Donald. Wyman's Gardening Encyclopedia. Macmillan Publishing Company. 1997
Beware of Streetlights’ Effect on Fall Bloomers. Msstate.edu