Cosmos flowers, members of the genus Cosmos, are widely cultivated annual plants known for their delicate, daisy-like blooms and feathery foliage. Gardeners choose these flowers for their vibrant colors and long blooming season. Cosmos can be an excellent food source for pollinators, but their usefulness depends heavily on the specific variety chosen. Selecting the right type of cosmos ensures that bees and other beneficial insects can effectively access necessary resources.
The Pollinator Appeal of Cosmos
Cosmos flowers serve as a source of nutrition for a wide variety of foraging insects, including honey bees, bumblebees, and native bee species. These blooms produce quantities of both nectar and pollen, making them a dual-purpose resource. Nectar provides the carbohydrates needed for energy, while pollen supplies the proteins and lipids required for feeding larvae and maintaining colony health.
The structure and visual appeal of the flowers contribute to bee attraction. Cosmos blooms present a large, open landing platform, which makes access easy for many types of bees. Planting cosmos in dense groups, often called “drifts,” creates a mass-planting effect that is visible to foraging insects, signaling a concentrated food source. Because cosmos bloom from mid-summer until the first frost, they offer a consistent food supply late into the season when other sources may be dwindling.
Structure Matters: Single Versus Double Petals
The physical architecture of the cosmos flower determines its value to bees. Like all plants in the Asteraceae family, each “flower” is a composite flower head called a capitulum, composed of an outer ring of sterile ray florets (petals) surrounding a dense center of fertile disk florets.
Single-petaled cosmos varieties are beneficial because they leave the central disk florets exposed and accessible. These disk florets contain the plant’s reproductive parts, which are the source of pollen and nectar. Bees can easily land on the open flower and quickly forage for the nutritional rewards within the central disk.
In contrast, double-petaled or hybridized varieties, such as those with ruffled or layered blooms, are less useful to pollinators. In these ornamental cultivars, many fertile disk florets are replaced by extra, sterile ray florets, physically blocking the central area. This makes it difficult for bees to reach the remaining pollen and nectar.
Selecting the Best Varieties for Bees
To maximize the benefit to pollinators, gardeners should choose varieties known for their simple, single-petal form. Two species are well-regarded: Cosmos bipinnatus and Cosmos sulphureus.
Cosmos bipinnatus, often called Garden Cosmos, includes popular mixes like ‘Sensation Mix,’ which produces a range of pink, white, and crimson single flowers attractive to bees. Cosmos sulphureus, known as Sulfur Cosmos, is prized for its bright yellow, red, and orange single blooms. Varieties such as ‘Bright Lights’ or ‘Cosmic Yellow’ are excellent choices, offering open access to their centers.
When planting these varieties, avoid over-fertilizing, as rich soil can lead to excessive leafy growth and fewer flowers. Allowing the plants to stand late into the season, instead of rigorous deadheading, provides a continuous food source and allows the plants to self-seed. This ensures a return of bee forage the following year.