How to Plant and Care for Mums—the Fall Showstoppers That Fill Gardens With Color

When you think of autumn flowers, there is likely one bloom that comes to mind: chrysanthemums. The plants line porch steps, suspend from hanging baskets, and dot flower beds come fall, bringing unbeatable color and charm to the landscape. Chrysanthemums, also known as mums, can bloom as early as August but thrive during September and October when temperatures are more mild. Available in a range of colors, from yellow and bronze to purples and white, mums can bloom for up to 10 weeks (and return year after year) with proper care.

Garden Mums vs. Florist Mums

Mums can be split into two broad categories: garden mums and florist mums. "Garden mums are bred from winter-hardy species, so if you plant them in the right conditions, they’ll come back every year," says Justin Hancock, horticulturist for Costa Farms. "Florist mums are not bred for their ability to come back every year, and are best treated as short-term annuals."

If you're growing mums in pots for seasonal color, the type you get doesn't matter. But if you’re growing them in your garden as perennials, you’ll need to be a little more selective. "The best way to know if a mum is a garden mum is to look at the plant tag and check the hardiness information, as visually they’re not always very different," says Hancock. Typically, garden mums are hardy to USDA hardiness zones 5 to 9.

How to Plant Garden Mums

Growing mums in your garden is an easy way to fill your fall landscape with color year after year. "For the greatest visual impact, mums should be planted in large swaths of the similar color with just a little bit of space between the edges of the plants so they are just about touching," says Tom Morris, director of public gardens and landscapes for the Pennsylvania Horticultural Society. "This gives each plant visual interest but also prevents the leaves from rotting due to trapped moisture from low airflow due to tightly placed plants."

1. While your mum is in its container, use your fingers to feel for soil moisture around the roots.
2. If the soil is dry, soak the bottom of the pot in water for at least five minutes or until all the soil is moist to the touch.
3. Pick a well-drained, sunny location in the garden to plant.
4. Remove the mum from its container and gently tease roots by hand to prevent tangled root systems.
5. Dig a hole in the ground and place your mum in the hole. Plant it at the same height it was in the container or slightly deeper to help root growth.
6. Backfill the hole with soil and water well.
7. Apply well-composted mulch around the base of the plant to help moisture retention, being careful not to place mulch against the base of the plant or cover the lower leaves.
   

Growing Mums in Containers

Both garden mums and florist mums can be grown in containers. Potted florist mums should be viewed as annuals and composted at the end of the growing season. Potted garden mums can be overwintered and planted in the garden come spring. If your garden or florist mums are root-bound, they likely need to be repotted to give them more room to grow.

1. Fill the new container with potting mix.
2. Slip the mum out of its current pot and loosen the roots. (Loosening the roots prevents two different moisture zones from forming since the new soil might hold water at a different rate than the old soil, says Hancock.)
3. Place the mum in its new container and fill with potting mix.

How to Care for Mums

In order to encourage your mums to bloom all season long, knowing how to care for the fall perennial is essential.

Sun

Mums need at least six hours of direct sun in most areas. "In especially hot, dry areas, you might look for some shade during the hottest part of the afternoon to help the mum last longer," says Hancock. "You can technically plant mums in a shaded garden, but without sufficient sun, they won’t have the energy to produce as many blooms and they’ll be more susceptible to attack from pests and diseases."

Water

Potted mums don’t like to dry out, so it’s best to water them once the top half soil starts to dry. "Take care not to overwater, though—if the soil stays wet, the roots can suffocate, die, and rot," says Hancock. For mums that were planted in the ground this year, you’ll want to water once the top few inches of soil start to dry. Established mums can typically withstand the top few inches of soil drying before they start to suffer, Hancock says.

Soil

Whether in pots or in the landscape, mums need a well-draining mix so they don’t stay wet. "In containers, just about any potting mix designed for container plants should do the trick nicely," says Hancock. "In gardens, they prefer a soil that’s rich in organic matter, though sandy or silty soils are typically fine."

Fertilizer

If you’re planting mums in pots for seasonal color and tossing them in the compost after they’re done, you don’t really need to fertilize them, says Hancock. If you're growing mums in the landscape and your soil isn’t the best, fertilize in spring as they start to grow using a general-purpose fertilizer.

Temperature

Mums like temperatures between 60 and 75 degrees with higher humidity, says Morris. "This is why mums do so well in the fall when the days are warm and nights are cooler—the temperature differences cause dew to form, helping keep the mums damp," he says.

How to Prune Mums

If you're growing mums as a perennial, wait until after they have finished blooming in the fall and the foliage has gone completely dormant to prune them. Then, cut the dead stems back to just above the ground. Alternatively, northern gardeners can leave the dead stems there to help insulate the roots from severe cold weather during winter, says Morris.

Once the plants emerge in the spring and begin to grow, cut them back no later than July so you have blooms in the early fall. "Prune them down to about 12 inches tall and give them a dose of a well-balanced water-soluble fertilizer like 10-10-10 to stimulate growth," says Morris.

Pruning in fall is only necessary if the flowers have faded and there’s still a few weeks before freezing temperatures arrive, says Hancock. Just a light trim to stimulate new growth is all that's needed.

How to Propagate Mums

The easiest way to propagate garden mums is to divide them. "As garden mums grow, they throw up new stems every year and can eventually form clumps a couple of feet across," says Hancock. You can dig up a corner of one of the clumps and replant it as long as it's healthy.

If you want to propagate a mum that hasn’t grown enough to be divided, then take cuttings.

1. Pinch off the top 3 to 6 inches of growth from the end of a stem. Remove any flowers or buds.
2. Plant the stem in a moist, humid environment in a medium like sand, perlite, vermiculite, or even potting soil. (If temperatures are warm and there’s enough moisture in the air, mums should start to root in a few weeks, says Hancock.)

How to Overwinter Mums

If you live in an area where mums are winter hardy, the plant will pretty much take care of itself. "If you’re in an area where it may not be as hardy, spreading a layer of mulch over the soil after the soil freezes can help give extra protection," says Hancock. "In general, it’s best to add a few inches of mulch if you do this."

Common Problems With Mums

Despite being relatively easy to care for, there are a few common problems gardeners run into when growing mums.

Pests

Mums are relatively resistant to pests, but you may see aphids, spider mites, or leaf miners, says Hancock.

• Aphids: Small, sap-feeding insects that often cluster at new growth, aphids can be treated by spraying them off the plant with a strong stream of water from the garden hose. "Do this every few days until you don’t see any other aphids," says Hancock.
• Spider Mites: This pest sucks up plant sap and typically lives on the underside of plant leaves, and may be difficult to see without magnification. "Their tell-tale sign is the webbing they create," says Hancock. "Spider mites are most commonly problematic in hot, dry conditions." Treat spider mites with a miticide or insecticidal soap.
• Leaf miners: Small flying insects whose larvae chew tunnels through the center of plant leaves, leaf miner damage is typically superficial. "Unless there’s an especially high population, you don’t usually need to worry about treating leaf miners," says Hancock.
  

Diseases

Mums aren’t quite as disease-resistant as they are pest-resistant, says Hancock. "A number of fungal diseases can cause yellow, brown, or black spots on the leaves, as well as early defoliation and reduced blooms," he says.

• Rust: A fungus that often attacks mums, rust causes yellow spots on leaves with orange spots underneath the leaves.
• Powdery mildew: This fungus typically affects the leaves of mums, causing them to appear to have a dusty white powdery coating that causes early leaf drop.

To prevent these common diseases, ensure mums have good airflow (not planted tightly against other plants or buildings) and don’t get too much water on the foliage, says Hancock. Additionally, fungicide applications may be applied when the disease first attacks the plant to prevent its spread.