Blue-eyed grass (Sisyrinchium species) is a perennial often found in gardens and natural landscapes. Despite its common name, it is not a true grass but belongs to the Iris family (Iridaceae). Gardeners often wonder if this plant spreads aggressively or is considered invasive.
Defining Invasiveness
An invasive species is defined as a non-native organism whose introduction to an ecosystem causes or is likely to cause environmental or economic harm, or harm to human health. These species often spread rapidly and can outcompete native plants for resources, reducing biodiversity. It is important to distinguish between a plant that spreads readily in a garden setting and one that is ecologically invasive. A plant can be aggressive in a cultivated space without meeting the criteria of an invasive species in a natural ecosystem.
Is Blue-Eyed Grass Truly Invasive?
Most blue-eyed grass species are native to North America, including widespread regions across the United States and Canada. For example, Sisyrinchium angustifolium is native to eastern North America, from Florida to Canada. Since these species are indigenous to the continent, they do not fit the ecological definition of an invasive species. They are part of the natural flora and contribute to local ecosystems, often found in meadows, prairies, and open woodlands.
Understanding Blue-Eyed Grass Spread
While not ecologically invasive, many blue-eyed grass varieties can spread enthusiastically within a garden environment. This spread primarily occurs through two mechanisms: self-seeding and rhizomatous growth. Blue-eyed grass produces small seed capsules after flowering, which readily germinate and establish new plants. Additionally, clumps expand through underground rhizomes, allowing them to naturalize. This vigorous growth can lead gardeners to perceive it as aggressive or “weedy,” particularly in lawns where it might outcompete turfgrass.
Managing Blue-Eyed Grass in the Garden
To control the spread of blue-eyed grass, several strategies can be employed. Deadheading, or removing spent flowers before they set seed, is an effective way to prevent excessive self-seeding. Dividing clumps every two to three years helps maintain plant vigor and manage size, also offering an opportunity to propagate new plants. Choosing appropriate planting locations, where some naturalization is acceptable or the plant can be easily contained, also contributes to effective management.
Advantages of Blue-Eyed Grass
Despite its spreading tendencies, blue-eyed grass offers benefits, making it desirable for many garden settings. It is low-maintenance and, once established, can exhibit drought tolerance, though it prefers moist soil. Its star-shaped blue or violet flowers with yellow centers provide early spring to early summer color. It attracts pollinators like bees and butterflies, and its seeds feed birds, contributing to garden biodiversity.