Sweet Violet ( Viola odorata )
Sweet and Hairy Violets form a pair of species that are distinct from the Dog Violets in having very blunt ended sepals.
The various species of Dog Violets have pointed sepals. The length of the sepal appendage can be important in separation of Dog Violets.
Violets can be tricky to identify as species are prone to considerable variation and hybridisation but the sepal shape is consistent and reliable to determine Sweet/Hairy Violets from Dog Violets.
This post looks at the variation in Sweet Violets based on the BSBI Handbook.
Usually regarded as native, however the Sweet Violet has a long history of been grown in gardens and in horticulture. Violets were grown on a massive scale in France and in Britain they were harvested for chemicals (used as an indicator and later as a scent extract) and also as cut flowers. There is a book that covers this subject , Violets The History and Cultivation of Scented Violets by Roy E. Coombs and its covers the many of the cultivars that resulted in all this horticultural activity.
Types covered are:-
Viola odorata var. odorata ( Standard type, violet flowers)
Viola odiorata var. imberbis ( White variation found in southern half of Britain)
Viola odorata var. dumetorum ( White variation occurs widely, especially common at edge of range)
Viola odorata f. lilacina ( often found where violet and white forms occur together)
I guess that at least three native forms of Sweet Violets were present before man started to breed different versions. First is the classic violet coloured Viola odorata var. odorata and the second is the white version Viola odorata var. imberbis. Fortunately both grow in the field behind my house plus a mixture of the two which might fit Viola f. lilacina.
Viola odorata var. odorata. 1st April 2018 Rampton, Cambridgeshire.
The standard type with violet petals has inner hairs on side petals, some hairs on flower stem, violet spur.
Viola odorata var. odorata 2nd April 2018. Rampton, Close up to show hairs on side petals and a bold pattern of purple veins splitting into thinner veins but still clearly defined.
Viola odorata Var. imberbis
Voila odorata var. imberbis 2nd April 2018, Rampton, Cambridgeshire.
A lot of flowers can have white variants but the flower colour is not the only change here, so more is going on. It might suggest variants or sub-species of Sweet Violet are evolving into separate species but have not quite reached that point. Several differences seen on this white form are the lack of hairs at the entrance to the inside of the spur on the side petals and the lack of hairs also on the flower stem or leaf stems. No purple veins present. Typical of this variant is the pinkish spur. This adds up to quite a few differences apart from the white petal colour.
Viola odorata f. lilacina (a form, possibly a mix of the above variants?)
A form rather than a variant. This particular flower was selected as it is at the palest end of the range present and grows about 20m from the normal violet and white types present in Rampton. Other plants have a more purple flushed appearance. This intermediate form may not be related to the presence of purple and white types nearby, all I can say is that they have been present for at least six years and were not planted while I have lived in the house ( 25 years).
Viola odorata f. lilacina , a pale example showing inner white hairs to side petals and hairs on flowering stem. Almost white with a few purple streaks. Spur is purple. 1st April 2018, Rampton.
Same flower but side view showing slightly distorted spur ( odd shaped spurs are often a feature of Hairy Violet (Viola hirta ) but this may be in this case due to this form being a mixture of two variations ?. ) , purple spur colour, quite hairy stem and of course the blunt round ended sepals.
Different flower showing more purple streaking to show a more typical example. Note the inner hairs are prominent on the side petals.
Viola odorata var. dumetorum
Not in Rampton but photographed on the Devils Ditch near Stetchworth, Newmarket. 25th March 2018. Similar to ver. imberbis with pure white petals but different as this var. has inner side petal hairs. Spur colour is purple and flower stem with some hairs.
Side view of same flower.
Conclusion.
Sweet Violet has several variants which have consistent characteristics and these are covered in the BSBI Handbook. The examples covered here are more likely to be native, with other colour types probably likely to be either introductions or escapes from horticulture. Sweet Violet also hybridises with Hairy Violet ( Viola hirta ). Hairy Violets 'always' have some new leaf stems with longer and often more patent hairs however it is not always easy to separate them. The hybrids have intermediate hairs and are often vigorous but the real problem is that the hybrid can backcross and form types that range from Sweet to Hairy in their characteristics.
Quite how two variants came to be in the field behind my house in Rampton is not known, but the intermediate form was one of the first plants I attempted to identify when I started getting into botany and this lead onto my attempts to understand Violets. I thought this would be an easy group but was totally wrong as the Dog Violets are a very complex group. See previous blogs for more on Dog Violets.
Peter Leonard
2nd April 2018
Reference.
Michael Porter and Michael Foley. Violas of Britain and Ireland BSBI Handbook No 17
