Spider Mum: Plant Care & Growing Guide (2024)

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.

Light

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.

Soil

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.

Water

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.

Fertilizer

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.

Pruning

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:

1. Use a shovel to dig up the entire root ball of the plant.
2. 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.
3. 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.
4. 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.

Overwintering

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:

Browning Leaves

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.