Why Aren’t my Mums Blooming? 7 Fixes to Try

Chrysanthemums are a hallmark of fall, delighting garden beds and containers in jewel tones of the season. From flared and spidery to pom pom and button, chrysanthemums feature different floral forms to celebrate autumn. They bloom in profusion until frost, setting their buds over the summer for the big show as day length shortens and temperatures cool.

But what happens when those blooms you were looking forward to don’t appear? There are several reasons why this might happen, and many of them are easy to fix or prevent.

Whether a hardy garden mum with years of recurrent color or a florist mum to highlight the entrance, we’ve got tips to keep mums in color. If your mums are not blooming, there are fixes to try now, as well as ones that boost vigor throughout the year.

Know Your Mum

If you’ve just purchased a potted nursery mum, care and treatment will be a bit different from that of hardy garden mums.

Both need little tending, aside from a few key cultural requirements, but those from a greenhouse are built to show right in time with fall, putting all of their energy into a profusion of single-season blooms.

Those in the perennial border develop sturdy roots and leafy uppers before budset, and benefit from basic well-timed tasks during the summer to promote the most vigorous flowering come autumn.

Chrysanthemums are clumping perennials, with hardy species that perennialize in USDA zones 5 to 9 (sometimes zone 4). The genus belongs to the aster family, Asteraceae, and they make beautiful companions to their fall-flowering relatives.

There are about 20 species of garden mums, which rely on underground shoots (stolons) to increase their winter survivability. Hardy garden mums are usually available at garden centers in the spring for planting and growing all summer.

Florist, or annual mums, are often less hardy due to fewer stolons, and may have the best success in warmer zones 7 to 9. If keeping potted mums, overwinter them indoors and plant them out in the spring. They may show less flowering in successive seasons after their forced initial bloom.

When picking a nursery potted chrysanthemum, look for one with loads of buds that aren’t yet open. If your mums are not blooming, they may have done most of their flowering already.

Provide More Sun

If your mums are not blooming, the first thing to check is sun exposure. They grow best in four to six hours of sunlight daily. While they tolerate some shade, they’ll show fewer flowers and leggier stems without enough sun. 

Plenty of morning sun exposure is optimal, in an east or south-facing position. If your potted mum is full of buds but not yet booming, a day or two in bright, warm sun accelerates their opening. Conversely, to delay opening, a bit more cooling shade during the day slows the progression.

For mums in the ground, prune away encroaching plants and overgrowth to allow more light infiltration. If the zone has become too shady, transplant the perennial. In the fall, move mums if there are at least six to eight weeks before the first frost. Roots need time to establish before freezing conditions. Or, wait til spring to move or divide the specimen.

Aim for Even Moisture

Mums that are not blooming may be experiencing water fluctuations. The perennials do best with evenly moist, well-draining soils. They need about one inch of water per week, or when soils dry to one or two inches deep. While they weather short dry spells once established, the heaviest flowering appears with consistent moisture. 

Soils and pots with good drainage are essential for root health, as overwatering leads to fungal problems like rot. Watering fluctuations stress the plants, and as they survive the extremes, they become more susceptible to pests and diseases, in addition to a pause in producing new growth and buds.

Check pots often, as they dry out more quickly than in-ground plantings, especially during warm days. They may need water every day or two until temperatures cool. Do a soil check or lift the container. If it feels light, give plants a thorough watering.

Time Fertilizing

Potted nursery mums are ready to roll off the shelves, already fertilized, and don’t need added nutrients to flower. There’s no need to promote new growth for the seasonal bloomers. 

In-ground, hardy chrysanthemums prefer rich, loamy soils with good drainage. Neutral to slightly acidic soils are optimal, with an ideal pH between 6.5 and 7.0. A soil test helps determine pH levels and nutrient levels at a given site. Amending in the fall gives soils ample time for absorption by the spring growing season.

In rich soils, hardy mums don’t require fertilizer to grow and bloom. But if your mums are not blooming, a boost in nutrition does offer early support that helps later flowering. It limits premature budding and blooming by promoting leafy growth prior to the bud stage.

Timing is important in feeding mums and is valuable during their vegetative stage (pre-budding) in spring and early summer. The application supplies nitrogen and potassium to support healthy leaf and root development. Fertilize mums before the bud stage and before the summer heat. This means a spring and summer application, depending on fertilizer type. 

Overfertilizing or a late application could also be the reason your mums are not blooming. Too much nitrogen leads to overproduction of leaves and stems, and the result is leggy, floppy branches with few buds and blooms.

Pinching, Pruning, and Deadheading

A potted annual mum is pre-shaped and won’t need pruning, but trimming hardy mums during the growing season keeps branches from getting long and leggy. It maintains a mounded, leafy form and promotes uniform budding. 

Pinching

The first light pruning is to pinch the stems during their spring growth spurt. Wherever you pinch or trim, new growth develops. Two to three rounds of pinching in spring and early summer foster the best development.

Pinching too late into summer limits time for bud development. Beyond early summer, it prevents buds from forming, resulting in mums not blooming. Buds need several weeks to fully form for the autumn display. Stop pinching by mid-July for healthy buds on well-formed plants.

Deadheading

Deadhead mums to keep the color going through frost. Removing spent flowers directs energy to existing, unopened buds. It exposes concealed buds along the stem, promotes continued flowering and root development over seed production, and tidies the look.

Deadheading isn’t essential to growth and won’t be the reason your mum isn’t flowering to begin with, as chrysanthemums set all their buds by about mid-summer. It does, though, encourage a long-lasting season, retain the best form, and support sturdy roots for overwintering. 

At peak flower, deadheading two or three times a week may be in order. A single sweep more frequently makes the process quick and easy. Remove spent flowers when they begin to wither and lose their color. Try to catch them before they turn brown and dry, which means seed production is underway. Cut stems back to a healthy set of leaves, concealing the fresh cut.

Scout for Pests and Diseases

Beyond their autumnal ornament, chrysanthemums attract beneficial insects like ladybugs, hoverflies, and lacewings, which prey on common pests like aphids and spider mites.

Their intrinsic essential oils and aromatic toxins make the surrounding area less attractive to invading insects. But, they don’t deter all pests and can fall prey to common and genus-specific insects.

Insect infestation could be the reason your mums are not blooming. Sap-feeding pests like aphids, spider mites, and whiteflies are often the main offenders in mums.

In mild cases, rub a cotton swab dipped in isopropyl alcohol over the population. Or, spray plants with a streaming hose to displace the insects from leaves and stems (taking care not to break the fragile branches). In severe cases, insecticidal soaps and horticultural oils like neem can rid outbreaks.

Clip off damaged, diseased, and dead stems at any time of the year. Removal prevents the spread of fungal diseases like root rot, powdery mildew, and botrytis that enter through wounds and insect feeding.

Diseases

Good air circulation with proper spacing is essential for preventing fungal diseases in mums. A disease-stressed plant will drop blooms or fail to produce them. Plant them at least 18 to 24 inches apart, depending on the variety, for plenty of airflow around stems and leaves.

Root rot, botrytis, rust, and powdery mildew are among the most common. To prevent these, allow good airflow and water consistently for even moisture. Avoid wetting the leaves unnecessarily to limit humid, damp conditions and the spread of spores through splashing. Horticultural oils can help treat early infections.

Wilt and viruses, like tobacco mosaic virus, are more serious and cause a quick decline. There’s no treatment for these, and removal is the best course of action to prevent the spread.

Plant at the Right Time

Setting the perennials up for success means planting them at the right time. The best time to plant mums is in the fall or spring when roots can establish before freezing or hot temperatures. For fall planting, six to eight weeks before heavy frost helps roots develop before winter.