This section is from the book "Wayside And Woodland Blossoms", by Edward Step. Also available from Amazon: Wayside And Woodland Blossoms: A Guide To British Wild-Flowers.
We have already given the general characters of the Violet family on page 4, where the reader was referred to this page for a notice of the British species other than V. odorata. The present species, V. tricolor, differs from all the others in the fact that the two upper petals are very erect instead of leaning forward, and in the stipules being developed into large leaf-like organs. In addition, this species produces none of the cleistogamous flowers. The leaves, too, assume forms very different from those of the typical species. The flowers vary from white, through yellow to purple, or there may be a mixture of two or more of these tints. They grow in pastures and the waste corners of various fields, flowering from May to September, and are generally distributed. The other species are:
I. Marsh Violet (V. palustris). Growing among Sphagnum in bogs. Flowers lilac or white, scentless, and with short blunt spur. April to July.
II. Hairy Violet (V. hirta). Similar to V. odorata, but more compact, more hairy, the leaves narrower and more deeply toothed; spur long, hooked. Odour slight or wholly wanting. A local species occurring in dry soils. April to June.
III. Dog Violet (V. canina). Rootstock produced into a distinct stem, bearing flowers. Sepals narrow, pointed. Leaves not enlarging after flowering, as do those of V. odorata, palustris, and hirta; on long foot-stalks. Plant more or less smooth. Flowers from April to August, on banks everywhere.
IV. Wood Violet (V. sylvatica). Plant smooth. Central rootstock short, with a rosette of leaves, from which branches are given off all round. From these branches only are flowers produced. Spur short and broad. Leaves broad. Copses and woods. March to July. Often closely resembling V. canina, of which it may be only a variety.
V. Sand Violet (V. arenaria). A very rare, compact, hairy plant. Leaves much rounder than the preceding. Petals broad, pale blue. Spur short. Recorded from Upper Teasdale and Westmoreland only ; flowering in May and June.