Chrysanthemums, commonly known as mums, are a cornerstone of the autumn garden, providing a burst of color when most other flowers fade. While their spectacular display occurs in the fall, the foundational work that determines the plant’s shape, size, and bloom quantity happens in the spring. Understanding the specific needs of these hardy perennials during their initial growth phase is necessary for a successful fall show. This spring care routine applies to both established plants that have overwintered and new plants being introduced to the garden.
Initial Pruning and Stimulating Growth
The first step in spring care involves a thorough cleanup as new shoots emerge from the base of the plant. Overwintered mums should have their dead, woody stalks cut back decisively. Trim these old stems down to about four to six inches above the soil line, or to the ground if new basal growth is clearly visible.
Pruning removes old material that can harbor pests and fungal spores, promoting a healthier environment. Clearing surrounding leaf litter or debris is equally important for discouraging slugs and other early-season threats. Cutting back stimulates the plant to focus energy on new, vigorous growth from the crown, which is the foundation for a full, well-shaped plant.
Spring Fertilizing and Watering Needs
Mums are heavy feeders, and their nutritional requirements increase significantly during spring growth. When new growth reaches a few inches in height, typically after pruning, begin a regular feeding program. A balanced, water-soluble fertilizer (e.g., 20-20-20 or 15-15-15 NPK ratio) supports this rapid vegetative growth.
Alternatively, apply a slow-release granular fertilizer once in the spring for a steady nutrient supply. Nitrogen is especially important during this phase to encourage lush green foliage and strong stems before the plant shifts energy toward flower production.
Consistent moisture is necessary for spring establishment, but good drainage is paramount, as chrysanthemums will not tolerate “wet feet.” Deep watering is preferable to shallow sprinkling, ensuring the root zone is thoroughly saturated, but allow the soil to dry slightly between sessions.
Mastering the Pinching Technique
The most important structural maintenance task for chrysanthemums in spring and early summer is “pinching.” This process breaks the plant’s natural tendency toward apical dominance, which results in a tall, leggy plant with few flowers. Removing the growing tip forces the plant to produce side shoots, leading to a denser, bushier form and a higher number of blooms.
Pinching should begin when new spring growth reaches four to six inches in height. The technique involves removing the top half-inch to one inch of new growth, typically using a thumbnail and forefinger or clean snips. This initial removal triggers dormant buds below to activate and grow outward, creating a wider, more compact plant.
The process must be repeated consistently every two to four weeks as the new side shoots reach four to six inches in length. Each subsequent pinch further increases the branching, multiplying the number of potential flower stems.
The timing of the final pinch is critical, as mums are photoperiodic plants that set buds in response to the shorter days of late summer. Most gardeners stop pinching between late June and mid-July, with the Fourth of July being a common cutoff date in many regions. Pinching any later risks delaying flower bud formation or preventing them from developing before the first hard frost.
Dividing Established Clumps and Soil Preparation
Established chrysanthemum clumps (three to five years old) often benefit from division, which rejuvenates the plant and prevents overcrowding. Signs a mum needs dividing include reduced flowering vigor, a woody or dead center, and overall weaker growth. The ideal time for this task is early spring, just as new growth appears.
To divide, carefully dig up the entire clump using a garden fork to minimize damage to the shallow root system. Discard the unproductive, woody center of the plant. Replant the healthy, vigorous sections from the outer perimeter that have their own roots and new shoots.
These divisions should be replanted immediately into freshly prepared soil at the same depth as the original plant. Good soil preparation is necessary for both divisions and new spring plantings. Chrysanthemums thrive in fertile, loamy soil with excellent drainage, as they are highly susceptible to root rot in soggy conditions. Incorporating organic matter such as compost or well-rotted manure improves both fertility and drainage, providing an optimal growing medium.