Chrysanthemums, often called “mums,” are among the most cultivated ornamental flowers globally, celebrated for their diversity in form and color. Belonging to the Asteraceae family, this genus is native to East Asia and northeastern Europe. They are significant because they are one of the last flowers to bloom, providing color in late summer and throughout the fall season. Their visual appeal is due to thousands of horticultural varieties displaying a wide spectrum of hues including white, yellow, bronze, pink, red, and purple.
General Plant Structure and Foliage
Chrysanthemums are typically perennial herbaceous plants, though some varieties can develop a slightly woody base and are classified as subshrubs. The plants generally exhibit a bushy, mounding, or erect growth habit, with stems that can reach heights between 12 and 60 inches depending on the cultivar. The stems are usually upright and often have a dense tuft of short hairs, contributing to the plant’s overall texture.
A distinctive feature is its foliage, which is arranged alternately along the stem. The leaves are broad and ovate, though they are deeply lobed or toothed, giving them a jagged appearance. When handled or crushed, the leaves release a strong, characteristic aromatic scent, which is a key identifying trait. This aromatic quality is partly due to compounds like pyrethrins.
The Unique Anatomy of the Chrysanthemum Flower Head
The structure commonly perceived as a single chrysanthemum flower is a dense cluster of many tiny individual flowers, or florets, arranged into a composite flower head called a capitulum. This head structure is characteristic of the Asteraceae family. The receptacle, which is the platform for these florets, is surrounded by layers of protective green bracts known as phyllaries.
Within this capitulum, there are two distinct types of florets: ray florets and disk florets. Ray florets are the showy, strap-shaped structures on the perimeter, often mistaken for petals. These female flowers are responsible for the vast range of colors seen in cultivated mums. Disk florets are the small, tubular flowers that form the central “eye.” These are typically yellow in wild species and are considered perfect flowers because they contain both male and female reproductive organs. The ratio and transformation of these two floret types create the immense morphological diversity across the various chrysanthemum classes. In many highly cultivated varieties, the ray florets are so numerous and modified that they completely obscure the central disk florets.
Categorizing the Diverse Bloom Forms
Daisy-Like Forms
Chrysanthemums are horticulturally categorized into 13 classes, differentiated primarily by the shape and arrangement of their florets. The Single and Semi-Double forms are the most daisy-like, featuring a clearly visible central cluster of disk florets surrounded by one to seven rows of flat ray florets. The Anemone form is a variation distinguished by its raised, hemispherical, and often colorful central disk floret mass that overshadows the surrounding ray florets.
Incurve and Reflexed Forms
The Incurve and Reflexed categories represent two opposing structural forms. Incurve varieties, such as the Regular Incurve, are characterized by ray florets that curve smoothly upward and inward, creating a tight, symmetrical, spherical bloom. The Irregular Incurve can be much larger, with loosely incurving florets that close the center and may create a noticeable “skirt” of lower, drooping florets.
In contrast, the Reflexed class features florets that curve distinctly downward and outward from the center. These overlapping florets create a dense, flattened globe or mop-head appearance. The Decorative form is similar to the reflexed type but features a slightly flatter profile.
Pompon Forms
The Pompon class is easily identifiable by its small, fully double, and exceptionally globular shape. These blooms are dense, spherical balls of florets, ranging in size from tiny button types to nearly four inches in diameter. The central disk florets are fully concealed. The ray florets in this class curve uniformly either upward or downward to maintain the tight, compact, round silhouette.
Tubular Forms
Finally, the Spider and Quill forms showcase the most dramatic floret modifications. Quill chrysanthemums produce blooms where the ray florets are straight, narrow, and entirely tubular, radiating outward with open tips, giving the flower a spiky, bristled look. Spider chrysanthemums take this tubular form a step further, with very long, fine, and slender ray florets that often have curled, hooked, or twisted ends, creating a delicate, airy visual effect.