Zinnias, members of the genus Zinnia and part of the Aster family, are celebrated garden annuals known for their vibrant, long-lasting color. While often promoted for attracting butterflies, their value to bees and other pollinators is more complex. Whether zinnias are beneficial depends almost entirely on the specific variety planted. Understanding the physical structure of the bloom is the first step in selecting zinnias that serve as a reliable food source for local bee populations.
The Critical Role of Zinnia Flower Structure
A zinnia bloom is a composite head made up of numerous tiny flowers called florets. The large, colorful, petal-like structures are the ray florets, while the reproductive parts packed tightly in the center are the disk florets. The disk florets produce the pollen and nectar that bees rely on for nutrition and energy.
Single-flowered zinnia varieties are the most beneficial because their central disk florets are fully exposed and easily accessible. Bees can land directly on the open center to quickly gather the resources they need. Examples include the popular ‘Profusion’ and ‘Zahara’ series, as well as many heirloom or wilder-type single varieties.
Many modern zinnias are bred to be double-flowered, resulting in a pom-pom or dahlia-like appearance. The ray florets multiply in these types, covering or replacing the central disk florets. This physical barrier prevents bees from reaching the pollen and nectar, rendering the flower useless to a foraging insect. Choosing varieties that clearly display a visible, open center is the most important factor for supporting pollinators.
Nutritional Contributions: Pollen and Nectar Quality
When bees can access the resources, zinnias provide a reliable source of both energy and protein. The nectar secreted by the disk florets is primarily a source of carbohydrates, which provide the flight fuel necessary for foraging bees. This energy is quickly converted into honey for the colony’s long-term needs.
The pollen collected from the florets is the primary source of protein, lipids, and micronutrients essential for raising young bees, or brood. Pollen quality varies significantly across plant species; optimal bee nutrition requires a protein content of around 20%. While the specific protein content of zinnia pollen can vary, it contributes to a healthy, diverse diet when combined with other floral sources.
Zinnias are particularly valuable because they are highly heat- and drought-tolerant, maintaining bloom throughout the hottest parts of summer when many other flowers have faded. This continuous, late-season availability ensures a consistent food supply for bee colonies during a period when resources might otherwise become scarce. Mass plantings of open-centered zinnias provide a significant quantity of accessible pollen and nectar, supporting local bee populations.
Safe Gardening Practices for Zinnia Pollinators
Cultivating zinnias requires specific practices to ensure the flowers are available and safe for foraging bees. Gardeners must strictly avoid the use of systemic insecticides, particularly neonicotinoids. These chemicals are absorbed by the plant’s vascular system and are distributed throughout its tissues, including the pollen and nectar.
When a bee consumes contaminated resources, it can suffer from impaired navigation, reduced immune function, and reproductive issues, even at sublethal doses. To ensure a pesticide-free start, ask nurseries if plants have been treated or grow zinnias from seed. If pest control is necessary, opt for the least toxic options and avoid applying sprays while pollinators are active.
Planting zinnias in large groups, known as mass planting, makes them more visible and efficient for bees to forage. Maintaining a continuous bloom by removing spent flowers, a process called deadheading, encourages the plant to produce new blossoms throughout the season. These simple maintenance techniques maximize the overall resource availability, turning the zinnia patch into a highly productive feeding ground for diverse bee species.