Not to be semantically confused with :
Dog Rose (
Rosa canina) nor with Dog's Mercury (
Mercurianis perennis), nor with Dame's-Violet
(Hesperis matronalis), a Cabbage Family plant nor with Water Violet (Hottonia palustris) nor Dog's-Tooth-Violet (Erythronium dens-canis) a member of the Lily Family.
Easily mistaken for : other Violets and Dog-violets (see captions for differentiation)
Hybridizes with :
Your Author does not know if any of the above photos might be of any hybrids.
Teesdale Violet (Viola rupestris) to produce
Viola × burnatti which is found with the parents in Upper Teesdale, County Durham and is intermediate in most characteristics. It is sterile.
- Early Dog-violet (Viola reichenbachiana) to produce
Viola × bavarica which has sepal appendages (to be found at the rear of the sepal) which are intermediate in length. It occurs only rarely where both parents are found. Nearly all are sterile.
Heath Dog-violet (Viola canina) to produce
Viola × intersita is intermediate in leaf characteristics and habit. Found scattered on heaths and dunes where the parents cohabit. It is sterile.
Pale Dog-violet (Viola lactea) to produce
Viola × lambertii occurs frequently where Pale Dog-violet occurs and is intermediate in leaf and flower characteristics and in habit. Nearly all are sterile.
Some similarities to : several Pansies to which they are closely related but they are usually much taller and bushier except for Mountain Pansy (Viola lutea).
A feature of Common Dog-violet is that the basal rosette of leaves lacks a flower stalk, which is somewhere else nearby and has its own leaves on the flower-stalk. It is a native perennial growing in from sea level to 1075m high in the UK. It is common in woodland preferring a half-shady place, but is also found in hedgebanks, grassland, heathland, moorland and even on shingle amidst other plants and grasses, on rocks and cliff edges. Grows on all but the most acidic soils (such as peat-bogs). The notch in the very pale spur is also an identifying feature (but that may be present in the hybrids above also). It is only sparsely hairy if at all.
It can sometimes flower twice in a season, the second time, around July to October but usually lacking petals or failing to open, pollinating itself in the bud.
Cleistogamous flowers are flowers which are able to pollinate themselves by using flowers which do not open. This behaviour is well known in Peas and Beans (Fabaceae) but the largest genus of cleistogamic plants are Viola. Only a few specimens of Viola are actually cleistogamic. These flowers are usually much smaller than normal flowers and they do not open; this saves using up valuable resources in making a flower large enough to attract external pollinating insects. Cleistogamy is normally a retrograde step for flowers since, by self-pollination, they are not using the ability of normal cross-pollination to increase the gene pool for better resilience against changing conditions or new infectious agents. But it serves a useful purpose in being able to survive in harsh conditions. Changes to the genes, do, however, occur even during cleistogamic fertilisation, but certainly not as many as by normal pollination by other like plants. Some plants, such as Orange Balsam (Impatiens capensis), can become cleistogamic after being severely damaged, and this allows them to at least propagate themselves.
Some plant species are always cleistogamous and never seem to open their flowers, therefore cannot indulge in sexual reproduction - one such being a new species of orchid discovered in 2016 (namely Gastrodia kuroshimensis, which is in the tribe Epidendroideae) and was found on the tiny Japanese island of Kuroshima. This orchid also lacks chlorophyll; it's flowers are brown and its stem a pale fawn-brown and therefore cannot photosynthesize and are myco-heterotrophic (on underground fungi). [It is also true that most orchids, even ones which do possess chlorophyll (i.e. have green parts) and can photosynthesise are also dependant upon a symbiotic relationship with underground fungi for at least some of their nutrition - but they share other stuff with the fungi]