This is common across northern states and adjacent Canada, but much less frequent in warmer regions. Gray (1864) listed just New England and Penn. for its range at that time. Like amplexicaule, purpureum was not definitely recorded in Ky. until 1914, when Gm noted that is was "less common than the preceding." Both species are weedy winter-annuals in fallow fields or other disturbed ground, but purpureum is less tolerant of dry soils and can also occur more in woodlands. As with other species of the genus, purpureum has had much ancient medicinal use; the chemistry of these species includes diverse iridoids, phenylpropanoids and steroids (Yalçin & Kaya 2006). An unusual trisaccharide, manninotriose, has been found to accumulate at high levels in roots and stems of purpureum durng early springs; this compound may be involved in cold resistance of the plants, but could also have nutritional and pharmaceutical applications for humans (Santos et al. 2013).