Viola odorata L. is native to
Europe but naturalized in North America. Viola ignobilis Rupr. from the Caucasus and Iran is similar to
V. odorata. I don't think that enough natural variation of these two species has been used in breeding,
and the botanist-geneticist could introduce some novel variations.
Unlike most of the sweet violets, the Parma
violets are not hardy above USDA Zone 8 and withstand more sun: these differences suggest a more southern origin.
R. D. Meikle in 1963 was probably the first to suggest that the Parma violets are V. alba Besser from
central and southern Europe, particularly Italy. Thus, 'Marie Louise,' 'Swanley White,' 'Lady Hume Campbell,' and
'Parma' are all derived from V. alba not V. odorata. The parma violets were the principal
violets raised near Rhinebeck (New York), which once boasted 400 greenhouses filled with violets. More breeding should
be done on this species and its natural variation including subsp. Alba, subsp. Scotophylla
(Jordan) Nyman, and subsp. dehnhardtii (Ten.) W. Becke.
The so-called yellow sweet violet, 'Sulfurea,'
is not scented and may not be V. odorata. This has sometimes been classified as V. Vilmoriniana,
a name without botanical standing.
The native Confederate violet of North America,
V. sororia Willd.(V. papilionacea Pursh), has often been pawned off as V. odorata,
but differs in its scentless flowers, lack of runners, and abundant cleistogamous (unopened, self-fertile) flowers that shed
enough seeds to classify this species as a weed. Breeding of V. sororia with V. odorata yielded
the scentless 'Governor Herrick' and the misnamed 'Frey's Fragrant'.
The sweet violet has also been bred with the Russian
violet, V. suavis Bieb., which is native from Russia to northwestern France. The Russian violet is a hardy violet
very similar to the North American Confederate violet but sweetly scented. The Russian violet was introduced into England c.1820;
an early, improved form was 'Russian superb.' 'The Czar' appeared as an improved form in 1863 in Middlesex, and about the same
time another form of V. suavis, 'Wilson,' was introduced from Algeria and Turkey into Provence, France.
Viola catalonica Becker from northeastern Spain, V. jagellonica Zapal. From Poland, and
V. adriatica from the northwestern section of the former Yugoslavia are probably natural hybrids of
V. suavis and V. alba and should be sought for cultivation. At least artificial hybridization
of V. suavis x V. alba should be possible.
The genus Viola includes about 450 species. Exactly how
many are scented is unknown, but some other species might also be listed here and should be sought for further horticultural
development. Viola cornuta, the horned violet, has highly scented flowers lacking the sweetness of
V. odorata. Other species indicated to be fragrant in the botanical literature include:
|V. ambigua Walds. And
Russia to Macedonia and Eastern Austria
|V. mirabilis L.
|V. willkommii R. de
||From Northeastern Spain
|V. jooi Janka
||From Central Romania
|V. pinnata L.
||From the Alps
|V. diversifolia (D.C.)
||From the Eastern and
|V. fragrans Sieber
||From Greece and Crete.