As temperatures begin to warm in April, carpets of violets begin to bloom in midwestern states. These native wildflowers have a dense fibrous root system that are found in shady, fertile sites and prefer moist soils.
The common violet (Viola sororia) is a short-stemmed, herbaceous perennial native to eastern North America. It is characterized by its heart-shaped leaves and blue-purple flowers with white throats that bloom in early spring, although it may flower sporadically into late summer and flowers can vary in color to light lavender or mostly white. This native wildflower propagates through rhizomes and seeds and can spread vigorously, often making it a nuisance plant in gardens and lawns. However, the vigorous nature of violets can make it an excellent choice for a native groundcover to replace exotic or invasive species.
Often considered a weed by gardeners, as violets spread aggressively through lawn and garden beds, these native plants can be embraced as a low maintenance ground cover that thrives in moist and well drained soil and in partially to fully shady spaces.
The common violet is a host plant for some 14 species of greater fritillary, most commonly the Great Spangled Fritillary (Speyeria cybele) and the Meadow Fritillary (Boloria selene), as well as 16 lesser common varieties. Like monarchs whose larvae eat milkweed exclusively, the fritillary larvae only feed upon violets, so the presence of violets is essential for their survival. Adult Fritillaries feed upon nectar of many native flowers, including mints, common milkweed and Joe Pyeweed. The fritillary is yet another butterfly mistaken by novice butterfly watchers for its distantly related cousin, the monarch. Female fritillaries emit phenomes to attract males, and mate during the summer. Following mating, female fritillaries enter into a rest period called diapause for a few weeks, emerging in late summer to lay eggs near violets. Fritillaries may have scent detection so keen they can detect even faded violets by the scent of their roots to ensure spring food for its larvae, but each fritillary lays thousands of eggs to account for any error in laying eggs where larvae cannot feed. Fritillary caterpillars hatch in the fall and enter into diapause for the cold weather, finding shelter in nearby leaf litter and emerging the when the violets begin to grow.
Common violets are also a host for the mining bee( Andrena violae)a specialist pollinator, solitary in nature and common to the Eastern U.S. that exclusively feeds on violets. The violet miner is a gentle bee, vital in early spring ecosystems, that digs its own underground nest. Adults emerge for only a few weeks during the spring, a lifespan synchronized with the violet blooms.
A home gardener with a proliferation of violets can fight them or embrace these spring emerging wildflowers, essential to some of the butterflies many gardeners want to draw. A serious butterfly gardener will not use pesticides to attempt to control these aggressively spreading wildflowers. The most effective way to control or move these plants is to dig up them up, including their dense root system.