Violet Family (Violaceae)
Violet Family (Violaceae)
Species native to North America
The violet family (Violaceae) includes about 900 species of plants. Species in this family occur in all parts of the world, but are mostly in the temperate zones, and at high altitude in the tropics. The largest group in the family is the genus containing violets and pansies (Viola spp.), with about 500 species.
Most species in this family are annual or perennial herbs. The leaves are simple, commonly heart-shaped, and are alternately arranged on the stem, or arise from a basal rhizome. In most species the flowers are irregular, that is, they are composed of two complimentary halfs. The flowers of most species have both female (pistillate) and male (staminate) organs. Most species flower in the spring and early summer and have relatively large and showy flowers, sometimes grouped into an inflorescence. They typically produce fragrance and nectar to attract insect pollinators. Later in the growing season, some species also develop selffertilized flowers that do not fully open, an unusual trait known as cleistogamy. The fruit is a many-seeded berry or capsule.
The major commercial value of species in the violet family is horticultural. One species is important in perfumery, and a few are used as medicinals.
Species native to North America
Most species of violets native to North America are wildflowers of the spring and early summer. Blue-colored violets are relatively common, with some of the more widespread species including the wooly blue violet (Viola sororia), northern blue violet (V. septentrionalis), New England blue violet (V. novae-angliae), western blue violet (V. retusa), prairie or larkspur violet (V. pedatifida), and marsh violet (V. palustris).
Some of the more common white-colored violets include the large-leaved white violet (Viola incognita), kidney-leaved violet (V. renifolia), sweet white violet (V. blanda), and northern white violet (V. pallens). Yellow-colored violets include the hairy yellow violet (Viola pubescens), smoothish yellow violet (V. eriocarpa), and round-leaved yellow violet (V. rotundifolia).
The green violet (Hybanthus concolor) is a species found in moist forests of eastern North America.
Ornamental violets
Many species of violets and pansies and their diverse hybrids are grown in gardens as ornamentals, particularly as bedding plants. Most commonly cultivated are the so-called garden pansies (Viola x wittrockiana), a hybrid complex that is largely based on the European pansy (V. tricolor). Ornamental pansies are now available in diverse floral colors, including solid and mixed hues of blue, purple, red, yellow, and white. Some pansy varieties develop quite large flowers.
The English or sweet violet (Viola odorata) is also commonly cultivated as an ornamental plant, and it sometimes escapes from cultivation to become a minor weed of North American lawns. Less commonly cultivated species include the horned violet (V. cornuta) and the alpine violet (V. labradorica).
Other uses of violets
The sweet violet has been cultivated in large quantities in southern France for the production of a fragrant oil from its flowers, known as oil-of-violets. This oil is used in the mixing of perfumes and other scents.
KEY TERMS
Cleistogamy —This refers to flowers that do not open, but are self-fertilizing and set viable seed. Various species of Viola are cleistogamous.
Emetic —A substance that induces vomiting.
Inflorescence —A grouping or arrangement of florets or flowers into a composite structure.
Weed —Any plant that is growing abundantly in a place where humans do not want it to be.
The yield of one tonne of fresh flowers is only 0.98-1.51 oz (28-43 g) of oil-of-violets. Interestingly, this light-green oil only has a faint scent when in its concentrated, distilled state, but when diluted to about 1:5000 its odor becomes very strong. The scent of violets can now been synthesized by chemists, so natural oil-of-violets is now rare.
Sometimes the flowers of pansies are served as an attractive, edible garnish to well-presented, epicurean foods. Pansies are also sometimes candied as an exotic confectionary.
Some minor organic medicines are prepared from several species in the Violaceae, mostly for use as emetics. These medicinal plants include Anchietea salutaris, Corynostylis hybanthus, and Hybanthus ipecacuanha.
Resources
BOOKS
Hartmann, H.T., A.M. Kofranek, V.E. Rubatzky, and W.J. Flocker. Plant Science. Growth, Development, and Utilization of Cultivated Plants. 4th ed. Englewood Cliffs, NJ: Prentice-Hall, 2006.
Judd, Walter S., Christopher Campbell, Elizabeth A. Kellogg, Michael J. Donoghue, and Peter Stevens. Plant Systematics: A Phylogenetic Approach. 2nd ed. with CD-ROM. Suderland, MD: Sinauer, 2002.
Bill Freedman