Chrysanthemums, or mums, are the quintessential flower of the fall season, celebrated for their vibrant colors and hardiness. These popular ornamentals belong to the Asteraceae family, which also includes sunflowers and daisies. Gardeners turn to them to provide late-season color, but whether these flowers benefit insects like bees and butterflies is complex. The answer depends entirely on the specific variety of chrysanthemum chosen, making their role as a pollinator resource nuanced.
The Impact of Cultivation on Nectar Access
The structure of a chrysanthemum flower determines its value to a pollinator, and this structure has been drastically altered by cultivation. Wild chrysanthemums, much like daisies, are composed of a ring of ray florets (petals) surrounding a central disc of tiny, fertile disc florets. These central florets are the source of nectar and pollen that insects seek.
Modern hybridization has led to the development of “double-flowered” varieties, which are the tightly packed, round mounds commonly sold in garden centers. In these cultivated forms, genetic mutations have caused the flower’s pollen-producing stamens to transform into additional ray florets. This “doubling” dramatically increases the visual appeal for people but significantly reduces the amount of pollen and nectar available.
The proliferation of extra petals physically covers the central disc florets where the food resources are located. Pollinators, particularly bees and many butterflies, are unable to access the nectar or pollen buried deep within the dense bloom structure. If an insect cannot physically reach the reproductive parts of the flower, the plant offers no resources. Studies have shown that this explosion of petals can reduce the attractiveness of the flower to pollinators, either by blocking access or by lowering the plant’s overall nectar production.
The Importance of Late-Season Blooms for Pollinators
For the varieties that do offer accessible nectar and pollen, their late-season timing provides a valuable ecological service. Mums typically bloom in late summer and fall, a period when the flowers of many other plants have faded and died back. This makes them one of the last available food sources before winter.
Pollinators like late-season bees, including new queen bumblebees, and migrating butterflies, such as Monarchs, rely on these flowers. The nectar and pollen they collect are used to build up fat reserves, which are necessary for the bees to survive hibernation or for the butterflies to fuel their long migratory journeys south.
Providing a consistent food supply during this seasonal gap is important for the survival of these insect populations. Without these late-season resources, the food storage of insect pollinators would be depleted, making it harder for them to successfully overwinter or complete their migration. When a chrysanthemum variety is accessible to insects, its presence in the fall garden helps sustain the health and vitality of local bee and butterfly populations.
Practical Steps for Planting Pollinator-Friendly Varieties
Gardeners wanting to support pollinators should focus on selecting varieties that offer an open structure. Look for single-flowered or semi-double varieties, which resemble a traditional daisy with a visible yellow or green center. These “old-fashioned” types, sometimes referred to as cushion mums, have an open face that gives insects access to the nectar and pollen-rich disc florets.
When purchasing plants, avoid the highly decorative, globe-shaped, or tightly incurved varieties, as these are typically the double-flowered types with concealed resources. Seek out local nurseries, as many commercially grown fall mums may have been treated with systemic pesticides. These chemicals permeate the entire plant, including the pollen and nectar, posing a significant risk to visiting insects.
For successful growth, plant mums in a location that receives full sunlight. Even non-native varieties can attract a diverse array of insects, including bees and butterflies, when their flower structure is appropriate. By choosing single-petal varieties and sourcing them responsibly, you can ensure your fall display provides both beauty and sustenance for migrating and overwintering pollinators.