Chrysanthemums, commonly known as mums, are a signature flower of the autumn landscape, celebrated for their vibrant, dome-shaped blooms. While often treated as annuals for seasonal color, many varieties are hardy perennials that return year after year. Achieving robust stem growth and an abundant display of flowers requires a strategic approach to feeding the plant. Supplying nutrients at the correct times is directly tied to the mum’s ability to transition successfully from vigorous leaf and stem production to the final flowering stage, building the energy reserves needed for a spectacular fall show.
Spring Growth: The Initial Feeding
The first and most important feeding window occurs in the spring, coinciding with the plant’s emergence from dormancy or when a new plant is set into the garden. This initial application should happen only after the danger of a hard frost has passed, typically between March and May. Applying fertilizer too early can force tender new growth that will be damaged by freezing temperatures. The goal of this early feeding is to stimulate root growth and establish a strong foundation for the entire growing season.
A balanced fertilizer, such as a 20-20-20 or 15-15-15 formulation, is appropriate at this time to provide equal parts Nitrogen (N), Phosphorus (P), and Potassium (K) for overall health. Phosphorus supports the development of a resilient root system, which is crucial for perennial plants. This spring boost ensures the plant’s structural components are vigorous enough to support the heavy foliage and numerous flower buds that will develop later. Strong vegetative growth early on is directly linked to the plant’s capacity to bloom heavily in the fall.
Summer Maintenance Schedule
Following the initial spring application, a sustained feeding regimen is required throughout the late spring and summer months to support the plant’s rapid vegetative growth phase. This period is when the mum develops its size and bushiness, building the framework that will ultimately hold the fall flowers. Consistent nutrient availability prevents growth stagnation and supports the energy demands of repeated pruning, a common practice used to encourage branching and a denser form.
For gardeners using a water-soluble fertilizer, an application every three to four weeks is effective in maintaining steady nutrient levels. Alternatively, a granular, slow-release fertilizer can simplify the summer schedule, often requiring just a single application in late spring or early summer. These slow-release products, with ratios like 12-6-6, release nutrients gradually over approximately three months, covering the peak growing period. Maintaining this consistent feeding schedule until mid-summer is necessary to achieve a large, healthy plant capable of producing a high volume of blooms.
Choosing the Right Fertilizer and Application
The specific nutrient blend should align with the mum’s current growth stage, prioritizing Nitrogen during the vegetative phase to encourage stem and leaf production. Ratios high in Nitrogen, such as a 20-10-20 formulation, are recommended for the spring and early summer months. Nitrogen drives the lush, green growth characteristic of a healthy mum by supporting chlorophyll production and protein synthesis. As the season progresses, a transition to a more balanced blend ensures the plant receives the necessary Potassium to support water regulation and plant resilience.
Choosing between granular and water-soluble formulations depends on the desired feeding frequency and convenience. Granular fertilizers release nutrients slowly as they break down, offering a low-maintenance, long-term solution. Water-soluble products, mixed with water and applied directly to the soil, provide nutrients immediately and are useful for a more precise, frequent feeding schedule. Proper application involves distributing the fertilizer around the drip line of the plant, avoiding direct contact with the main stem or foliage. Always water the plant thoroughly both before and immediately after applying fertilizer to help dissolve the nutrients and prevent chemical burn.
Signaling Bloom: When to Stop Feeding
The final and most crucial timing decision is knowing when to cease fertilization to initiate the flowering process. Chrysanthemums are short-day plants, meaning they begin to set flower buds when the days shorten and the nights lengthen in late summer. Continuing to feed the plant with high-nitrogen fertilizer past this point counteracts the natural signal to bloom. Excessive nitrogen encourages vegetative growth, resulting in fewer flowers and a delayed bloom time.
The specific cutoff date for nitrogen feeding is typically late July or the beginning of August, depending on the local climate and desired bloom time. Stopping the feed at this point redirects the plant’s energy away from leaf and stem production and toward flower bud formation. New growth produced after this cutoff date would also be tender and more susceptible to damage from an unexpected early fall frost. This cessation of feeding is a deliberate practice that signals the plant to prepare for its autumn display.