How To Prune Mums For Strong Growth and Flowering

Hardy chrysanthemums light up the garden with seasons of autumnal color as perennials in USDA zones 5-9. With varying forms, colors, and flower shapes, they bring dynamic interest as other bloomers fade. Unique heirloom selections add variety and enchant in both antique and vibrant shades.  

Easy-care mums don’t require much to thrive in the border or containers. With regular moisture, sunlight, and healthy, well-draining soil, garden mums burst into bloom in fall and have soft, mounding foliage throughout the growing season. 

I sometimes forget about mums until delighting in their cheery return of colorful blooms on trailing stems. The thoughtful gardener can lightly prune early in the season for strong, upright stems and loads of buds. A quick sweep two to three times in the growth phase is all it takes for full, leafy forms.

Benefits of Pruning

Pruning hardy mums keeps branches from getting long and leggy or flopping over. It maintains a mounded, leafy form and promotes uniform budding. A light prune for the quick-growers is pinching back the stems during their early season growth spurt. Wherever you pinch or trim, new growth develops.

Deadheading, too, helps the robust bloomers stay in flower throughout the fall and sends energy to their roots. Cutting back dormant stems in winter or early spring gives room for soft new stems to emerge.

When to Prune

Nursery potted specimens are display-ready, already pruned and shaped for our autumnal arrangments. There isn’t a need to pinch or prune newly purchased potted mums unless you discover broken stems. Those in full flower benefit from deadheading to keep the blooms coming all season.

In the spring, established and new plantings benefit from pinching. For new plants, begin pinching about two weeks after planting.

Pinching new stems at various phases of development creates healthy, full forms and all-over flowering. This light pruning creates compact, sturdy stems for consistent budding and blooming. Two to three rounds of pinching during the growing season usually does the trick.

When stems reach about eight inches tall, begin pinching them back, and do so every few weeks (with every five to six inches of new growth). Depending on the variety’s bloom time, pinching occurs through late June or early July before buds set. Pinching too late into the summer prevents buds from forming, resulting in fewer flowers. Buds need several weeks to fully develop for the autumn show.

Mid-July is usually the cutoff to stop pinching and foster healthy buds on your well-formed plants. Many gardeners use the Fourth of July to mark their final pinch. 

Shorter day length periods in late summer and fall trigger blooming, and we want those buds to be numerous and sizable for the best flowers. Early-blooming varieties set buds more quickly than later bloomers; keeping an eye on your mum’s flowering time helps adjust timing the final pinch for the next season.

How to Prune

Another goal of pinching is to create an appealing shape. In pots, this is usually a broad, rounded form. In beds, this removes irregularities to create an attractive, full habit.

To pinch new stems, use your fingers to “trim” the tips. New stems are thin, tender, and pliable for easy pinching. Pinch to remove two to three inches from the end of the stem. You can also use snips or pruning shears.

As mums reache eight inches, pinch off any buds. Also, pinch off non-budded tips.

Growth tips are the fresh, light green stem ends. Removing these encourages side branching for more stems and buds. Every two to four weeks, pinch the growth tips from the new side shoots. This allows dense, compact foliage to develop.

Deadheading

Deadheading during the late summer and fall bloom period directs energy to remaining buds and flowers, keeping color going through frost. Deadheading, while not essential to growth, is a common practice to support remaining flowering and tidy up the plant’s appearance. Removing spent blooms is one of the simplest ways to encourage a long-lasting season while retaining the best form.

For mums, clipping off the faded flowers doesn’t promote new buds. It prevents plants from going to seed; instead, they channel the energy into present flowering and root development. More energy for growing, rather than reproduction through seed, enhances winter survivability. Peak season may call for deadheading two or three times a week to make the process quick and easy. 

Deadhead when flowers begin to wither and lose their color. To deadhead, cut or pinch off a single flower as it fades. This improves the appearance and allows the remaining buds and blooms to shine. Cut stems back a couple of inches to conceal the stem or to a healthy set of leaves.

Disbudding

Disbudding is a technique growers use for display-quality floral enhancements. In large-flowering varieties, disbudding directs energy to single, large buds and blooms rather than a series of less substantial ones. Small-flowered varieties don’t benefit from disbudding, as they won’t produce larger blooms as a result.

Disbudding means removing lateral buds in favor of the terminal bud. The terminal bud on the tip of the stem will soak up energy to form a larger, high-quality bloom. If you’re interested in a large, single bloom per stem, roll away the additional buds as close to the stem as possible when they are small. You can take all or leave those on the top two to three inches of stem to ensure healthy flowers.

Pinch off all but a few side shoots and remove buds other than the primary central flower bud. Waiting too long or removing full buds won’t help redirect the energy in time. Late removal may slow down development and lessen color intensity.

Spray varieties (clusters of smaller blooms along the stem) may develop larger, unstunted sprays by disbudding the central, terminal bud only. Leave the other buds for full color. This isn’t essential to growing or flowering.

Winter Cut Back

Once flowering finishes and heavy frost occurs, the herbaceous perennials enter winter dormancy. In cold climates, leave the dormant stems in place as insulating materials. Cut them back in early spring before new growth emerges within a few inches of the soil level. 

In lower growing zones, add extra mulch for cool-season protection. Use a light layer of mulch on crowns, or add evergreen boughs to protect against ice and frost heaving as soils freeze and thaw.

To overwinter the perennials in containers, place them in a cool, sheltered location like a garage or basement until the final frost passes in spring. Check the soil moisture level occasionally to keep roots from drying out completely.

Divide chrysanthemums every few years to expand the collection and renew vigor.

Scout for Pests and Diseases

While we’re clipping spent blossoms, it’s a good time for an overview of plant health. Easily pluck damaged leaves for disposal to prevent the spread of pests and diseases. 

You may see insects like aphids, spider mites, and whiteflies. In mild cases, a rub with a cotton swab with isopropyl alcohol may do the job. Or, in the early morning, spray plants with a streaming hose to knock them off leaves and stems (taking care not to break fragile branches). In severe cases, insecticidal soaps or horticultural oils like neem can rid plants of infestation.

Also, remove any damaged, diseased, or dead branches at any time of the year. Removal benefits the plants by preventing the spread of fungal diseases like root rot, powdery mildew, and botrytis.