Rosemary is a popular, aromatic shrub cherished by gardeners for its culinary uses and evergreen foliage. Gardens are often planned with the dual purpose of growing this herb and attracting the delicate beauty of butterflies. Understanding how the strong scent and small flowers of Salvia rosmarinus interact with flying insects is helpful for designing a flourishing ecosystem in the backyard. This exploration will delve into the biological relationship between this Mediterranean herb and the butterflies seeking nectar and host plants.
Rosemary as a Nectar Source
Rosemary flowers, typically appearing as small blue or lavender blossoms, do contain nectar, making them a potential food source for pollinators. However, the plant’s structure and nectar quantity mean it is generally a secondary choice for many butterflies. The small, tubular shape of the flowers makes it difficult for larger butterfly species to access the nectar efficiently.
Butterflies tend to seek out flowers with wide, flat surfaces that provide a stable landing platform while they feed. Rosemary flowers offer a less convenient surface, which means they are more frequently visited by smaller, shorter-tongued insects like honeybees and mason bees. Although rosemary is listed among herbs that attract butterflies for nectar, its contribution is often minimal when compared to more robust, larger-flowered garden plants. The herb is not considered a host plant, meaning butterflies do not lay their eggs on its foliage.
The Aromatic Effect on Insects
The distinct, pungent aroma of rosemary is due to high concentrations of volatile organic compounds that act as the plant’s natural defense mechanism. These chemical compounds are mostly monoterpenes, including substances like camphor and 1,8-cineole. The strong smell and toxicity of these oils serve to deter many common garden pests.
These aromatic compounds can actively confuse or repel insects, including certain butterflies. For example, the scent of rosemary is known to mask the odor of host plants like brassicas, which are the preferred egg-laying sites for the Cabbage White butterfly. By disrupting the chemical signals butterflies use to locate food or host plants, the herb creates a protective barrier for nearby vegetation. This characteristic explains why butterflies may pass over rosemary even when it is in bloom.
Companion Planting for Butterfly Attraction
Since rosemary is not a preferred nectar source, gardeners can still achieve their goal of attracting butterflies by strategically pairing it with other plants. Butterflies are often drawn to bright colors and flowers that offer a clear visual target and a sturdy place to land. Planting nectar-rich alternatives near rosemary allows the herb’s pest-deterring properties to benefit the garden without sacrificing pollinator activity.
Excellent nectar sources include plants with broad, accessible flowers like Zinnia, which provides both bright color and a flat landing pad. Another option is Coneflower (Echinacea), whose dome-shaped center is packed with accessible nectar. For those aiming to attract Monarchs, incorporating host plants like Butterfly Weed (Asclepias tuberosa) is essential, as this provides the specific foliage required for caterpillars.