Pansies (Viola x wittrockiana) are one of the most common cool-weather flowers, celebrated by gardeners for their vibrant colors and hardiness. These cultivated plants are hybrids derived from various Viola species, making them popular for garden beds and containers. Many people plant them assuming their bright, cheerful appearance will automatically draw in butterflies and other pollinators. The question of whether pansies are effective for attracting butterflies requires a closer look at the different resources these insects need throughout their life cycle.
Nectar Source Versus Host Plant
Understanding a butterfly’s life cycle is the first step in determining a flower’s true value in the garden. Adult butterflies require “nectar sources,” which are flowers that provide the sugary liquid fuel they need for flight and reproduction. These flowers generally have flat, easily accessible blooms or tubular structures that a butterfly can probe with its long proboscis.
Modern pansies, being highly cultivated hybrids, often fall short as quality nectar sources. The hybridization that created their large, showy blooms often resulted in flower structures where the nectar is too deep or scarce for a butterfly to efficiently access. While a butterfly may occasionally land on a pansy, it generally does not offer the rich, accessible energy source that better-suited flowers provide.
Pansies and the Fritillary Butterfly Family
While modern pansies are not a preferred fuel stop for adult butterflies, they serve an important purpose for one specific group. The Viola genus, which includes pansies, violets, and Johnny-jump-ups, is the exclusive host plant for the larvae of the Fritillary butterfly family. This relationship is so specific that the caterpillars of the Variegated Fritillary (Euptoieta claudia) are commonly nicknamed “pansyworms.”
A “host plant” is the specific vegetation a female butterfly must lay her eggs on, as it is the only food source the resulting caterpillars can eat. Once the eggs hatch, the larvae of the Fritillary butterflies feed on the leaves, flowers, and stems of the pansy or violet plant. Planting pansies, or their native relatives, provides the necessary environment for the next generation of butterflies to complete their metamorphosis.
For butterfly conservation, native violets are often better host plants than cultivated pansy hybrids. Native violets have not been bred for ornamental qualities, retaining the chemical compounds and leaf structure that Fritillary caterpillars recognize and prefer. Gardeners should prioritize creating a patch of violets where the caterpillars can safely feed and develop without disturbance.
High-Impact Nectar Alternatives
If the goal is to reliably attract and feed adult butterflies, gardeners should focus on flowers offering high-quality, easily accessible nectar. These plants have large flower clusters or open, flat surfaces that provide a stable landing platform. A consistent supply of nectar is necessary to sustain the adult butterflies’ energy needs throughout the season.
Flowers like Zinnias are excellent choices because their large, flat bloom heads provide a perfect resting area and produce abundant nectar. Coneflowers (Echinacea purpurea) and Asters are also highly effective. Asters, in particular, bloom in late summer and autumn, providing a food source for butterflies preparing for migration or overwintering.
Milkweed (Asclepias) serves a dual role, functioning both as a host plant for Monarch butterfly caterpillars and as a rich nectar source for a wide variety of adult butterflies. Planting a diverse selection of these flowers ensures a steady, season-long supply of nourishment. Prioritizing species known for their nectar content creates a more effective butterfly habitat than relying solely on cultivated pansies.