Chrysanthemums, commonly known as mums, are celebrated late-season flowering plants, offering a spectacular burst of color when most other garden blooms have faded. These hardy perennials provide dense, vibrant flowers in a wide array of shapes and hues. Achieving a spectacular display begins with understanding their fundamental needs and implementing specific maintenance techniques.
Setting Up the Ideal Location
Selecting the right planting spot is crucial for the health and flowering potential of your chrysanthemum. Mums are photoperiodic, relying on the shortening days of late summer to trigger bud formation, which requires five to six hours of direct sunlight each day. Morning sun is beneficial because it quickly dries dew from the foliage, helping prevent common fungal diseases like powdery mildew. Avoid locations near streetlights or porch lights, as artificial light disrupting the hours of darkness can delay or prevent flowering.
The soil must be well-drained, as chrysanthemums suffer root rot in standing water. A loamy or sandy soil is ideal, and incorporating organic matter, such as compost or peat, improves both fertility and drainage. The optimal time for planting perennial garden mums is in the spring, allowing the root system to establish before the first hard frost. If planting in the fall, aim to get the mum into the ground at least six weeks before the expected deep freeze.
Routine Care: Watering and Feeding
Water the plants deeply at the base, ensuring the root zone is saturated, rather than providing shallow, frequent sprinkles. Allowing the top inch of soil to dry slightly between waterings encourages strong root development and prevents the soil from becoming soggy. When watering, keep the foliage dry, especially in the evening, since prolonged moisture on the leaves creates an environment for fungal pathogens.
Chrysanthemums are heavy feeders and benefit from a regular supply of nutrients during their active growth phase. From spring until mid-summer, apply a balanced, water-soluble fertilizer (such as 10-10-10) every three to four weeks. This supports robust leaf and stem development. Once flower buds begin to form, switch to a high-potassium formula (such as 4-18-38) every two to three weeks to enhance bloom size and color intensity. Fertilization should cease by late summer or early fall to avoid promoting new, tender growth vulnerable to cold.
Shaping the Plant for Abundant Blooms
The horticultural practice of “pinching” is the most effective technique for maximizing the number of flowers a chrysanthemum will produce. This involves removing the soft, new growth tip of the stem, which temporarily halts the flow of the growth hormone auxin. By interrupting this hormone that maintains apical dominance, the plant activates dormant lateral buds, resulting in multiple side shoots that create a dense, bushy structure.
Begin pinching when the plant reaches a height of approximately six to eight inches in late spring, removing about half an inch to one inch of the stem tip. Repeat this process every two to three weeks as the new side shoots grow an additional four to six inches. The final pinch must occur by the first or second week of July, depending on your climate. Stopping the pinching by this mid-summer deadline allows the plant sufficient time, approximately 100 days, to set its flower buds for a spectacular autumn display.
Seasonal Protection and Overwintering
When the flowering season ends and a hard frost has killed the above-ground foliage, the plant enters its dormant stage. For garden mums planted in the ground, it is best to leave the dead foliage in place until the spring, or cut the stems back to about eight inches, providing some natural insulation. The primary threat to winter survival is the cycle of freezing and thawing, which can push the plant’s root crown out of the soil in a process called frost heaving.
Once the ground is solidly frozen, apply a thick, loose layer of winter mulch, such as straw, pine needles, or evergreen boughs, directly over the plant crown. This protective layer insulates the soil and maintains a consistent, cold temperature, preventing heaving. For chrysanthemums grown in containers, move the pot to a cool, dark, and protected location, such as an unheated garage or basement, where temperatures remain above freezing. Water these container plants sparingly to keep the roots from drying out during their dormant period.