Chrysanthemums (mums) are the defining flower of autumn, bringing a welcome burst of color when most other plants fade. Many people purchase these dense, dome-shaped plants in fall, leading to confusion about whether they are annuals or perennials. Mums bought at grocery stores or florists are often “florist mums,” which are generally treated as annuals due to their breeding and shallow root systems. Conversely, “garden mums,” or hardy mums, are perennial varieties bred to survive colder temperatures and return year after year. Understanding the difference and providing proper care is essential for maximizing their enjoyment.
The Seasonal Timing of Mum Blooms
Mums are scientifically classified as short-day plants, which explains why they bloom as autumn approaches. This is not a response to cooling temperatures but rather to photoperiodism, the plant’s reaction to the length of darkness in a 24-hour cycle. To initiate flower buds, chrysanthemums require long, uninterrupted periods of darkness, typically 10 to 12 hours or more, which naturally occurs as the days shorten in late summer and early fall.
Once a mum begins to bloom, its flowering is predetermined by the buds that have already set. Commercial growers sometimes use black cloth to artificially shorten the day length and force blooms outside the natural window. For the home gardener, natural daylight conditions dictate the bloom cycle, and this process cannot be easily reversed to force a new flush of flowers.
Maximizing the Current Flower Display
To keep the current flower display looking fresh and prolong the enjoyment of existing buds, specific maintenance techniques are necessary. The most important action is deadheading, which is the removal of spent, faded, or brown flowers. This practice prevents the plant from diverting energy into producing seeds, which is its natural reproductive goal once a flower fades.
By removing these spent blooms, you redirect the plant’s resources toward the development of remaining, unopened buds and strengthening the root system. Use clean scissors or your fingers to pinch or cut the faded flower head, tracing the stem back to a healthy set of leaves or a small side bud. Performing this task weekly maintains a tidy appearance and extends the overall bloom period. Consistent watering is also important, ensuring the soil remains evenly moist but not waterlogged. Avoid wetting the foliage, as this can encourage fungal diseases.
Ensuring Mums Return Next Year
If you have a hardy garden mum, preparing it for a perennial return requires focused attention on root survival. Plant the mum in the ground immediately after purchase, rather than leaving it in its original pot, to give the roots time to establish. Although spring planting provides the best establishment time, fall-planted mums can still survive with extra winter protection.
The main threat to survival is not the cold itself but the cycle of freezing and thawing, which can push the shallow roots out of the soil in a process called frost heaving. To counteract this, wait until the ground has fully frozen. Then, apply a thick, loose layer of mulch, such as straw or pine needles, four to six inches deep over the plant crown. This insulating layer maintains a consistent, cold temperature, preventing damaging freeze-thaw cycles. Do not cut back the dead foliage until early spring, as the old stems and leaves provide natural insulation and protection throughout the winter months.