Viola obliqua Hill.

Great American Violet

Variable rhizomatous species. Leaves ovate, deciduous; margin round-toothed. Flowers large, generally clear bright purple on stalks to 15 cm or so long, without fragrance; spring. [V. cucullata Aiton]

North America

Grows naturally in wet places.

Source: McLeod, J. (1997). Violaceae. In: Spencer, R.. Horticultural Flora of South-eastern Australia. Volume 2. Flowering plants. Dicotyledons. Part 1. The identification of garden and cultivated plants. University of New South Wales Press.

kingdom Plantae
phylum   Tracheophyta
class    Magnoliopsida
superorder     Rosanae
order      Malpighiales
family       Violaceae
genus        Viola L.