The Common Blue Violet (Viola sororia) is a low-growing, herbaceous perennial native to eastern and central North America. This plant features dark green, heart-shaped leaves and produces blue-violet flowers in early spring. Whether this wildflower is considered a desirable native plant or a persistent nuisance depends entirely on the location and the gardener’s perspective. The perception of Viola sororia as a “weed” typically emerges when its spreading nature conflicts with a manicured lawn aesthetic.
The Dual Identity of the Common Blue Violet
For many ecologists and naturalistic gardeners, the Common Blue Violet is a valuable component of the local ecosystem. As a native species, it provides one of the earliest sources of nectar and pollen for native bees and other pollinators emerging in the spring. The foliage is also a host plant for the caterpillars of several fritillary butterfly species. Furthermore, the leaves and flowers are edible, offering a source of vitamins A and C.
This positive classification shifts dramatically when the plant establishes itself in a turfgrass lawn or a cultivated garden bed. In a manicured setting, the violet’s aggressive spreading is viewed as a significant problem. Its dense, low-growing leaves successfully outcompete turfgrass for light and nutrients, leading to patchy lawns. The plant thrives in a wide range of soil conditions, from moist shade to full sun, making it a resilient invader that is difficult to suppress.
Identification and Aggressive Growth Habits
Identifying Viola sororia is straightforward due to its distinctive basal rosette structure, where all leaves and flower stalks emerge directly from the ground. The leaves are glossy, dark green, and deeply heart-shaped with finely scalloped edges. In the spring, showy, five-petaled blue-violet flowers, known as chasmogamous flowers, appear on leafless stems, relying on insects for cross-pollination.
The plant’s true persistence stems from two biological mechanisms that allow it to reproduce prolifically. The first is its network of short, fleshy underground stems, or rhizomes, which allow the plant to spread vegetatively and form dense colonies. These rhizomes store energy and make manual removal difficult, as any small piece left behind can regenerate a new plant.
The second mechanism involves the production of inconspicuous, non-opening flowers called cleistogamous flowers. These flowers are often hidden near the base of the plant and are self-pollinating, guaranteeing seed production even without insects. These closed flowers produce the bulk of the seeds, which are then dispersed through two methods.
The seed capsules of the cleistogamous flowers eventually split open and explosively eject the seeds a short distance. Additionally, each seed possesses a lipid-rich appendage called an elaiosome, which attracts ants. The ants carry the seeds back to their nests to feed on the elaiosome, effectively dispersing the intact seed and helping the violet colonize new areas. These combined reproductive strategies ensure the violet’s survival and aggressive spread.
Practical Management Strategies
Controlling the Common Blue Violet requires a multi-pronged approach because of its underground rhizomes and dual seed production methods. For small outbreaks, manual removal is a viable non-chemical option, but it must be thorough. Gardeners must use a trowel or small shovel to ensure the entire fleshy rhizome system is removed from the soil, as leaving fragments will result in regrowth.
Cultural control is the most effective long-term non-chemical strategy for lawns, focusing on creating a dense, healthy turf that outcompetes the violet. This involves mowing at the highest recommended height and overseeding thin areas to improve grass density. In landscape beds, applying a thick layer of organic mulch can suppress the germination of new violet seeds.
When chemical control is necessary, products containing standard broadleaf herbicides like 2,4-D are often ineffective against the violet. This is due to the plant’s thick, waxy leaf cuticle, which prevents the herbicide from being absorbed. Herbicides containing the active ingredient triclopyr are notably more effective, and products that include a combination of triclopyr and dicamba tend to perform best. Applying a liquid surfactant alongside the herbicide can help it penetrate the waxy leaf surface. The most effective time for application is in the fall, when the plant is actively transporting nutrients to its roots for winter storage, drawing the chemical down.