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Violets of the Ottawa District

John Gillett
Curator Emeritus/Research Associate, Canadian Museum of Nature

This article is reproduced from Trail & Landscape 31(2): 53-64, with permission.

Violets are synonymous with spring. The pansies of our gardens are violets. All of our regional violets are small herbs. However, the plant family Violaceae also contains a number of larger plants. For example, the Green Violet, Cubelium concolor (Forst.) Raf., a large herb that grows about 1 metre tall, occurs in southern Ontario in the Niagara region.

About 500 species of violets exist, most of them in the north temperate zone but some are found in the Andes. (I actually found one when botanizing in Colombia). The first garden varieties date from about 1820 when an Englishman named Thompson began crossing species and backcrossing the hybrids. The Johnny-jump-up is Viola tricolor L., but many of our cultivated pansies arose from hybrids with V. odorata L. (which is grown in southern France for essential oils used in the manufacture of perfumes and toiletries), and/or V. canina L., the Sweet and Dog Violet respectively. Many of our hybrids do not show any trace of V. odorata or V. canina characteristics and are derived from other species. Pansies can be grown as annuals, biennials or perennials. They need cool shade; heat quickly destroys them. Mine overwinter quite nicely by covering them with straw before the snow comes.

Many studies of the genus Viola have been made but few authors agree on the disposition of the numerous species that have been described. I have tried to simplify things as much as possible, drawing on two major studies, that of Ballard (1994) and an earlier one by McKinney (1992). None of the commonly consulted floras agree on the number or often the identity of species but that does not interfere with our right to enjoy these beautiful plants and to try to recognize them.

Reproduction of violets is, as in many other plants, either by division of the plants (asexual method) to produce clones of genetically similar plants or by sexual means, i.e., by pollination with transfer of genetic material between plants. There are two types of flowers, the showy flowers that we are all familiar with (called chasmogamous flowers) and inconspicuous flowers which never open (cleistomagous flowers) and which usually appear later in the season. The cleistogamous flowers pollinate themselves (called selfing) so there is no exchange of genetic material. Seeds are formed in this manner.

Selfing also occurs in the showy flowers but cross-pollination with other plants may occur, then there is an exchange of genetic material. However, most reproduction is either vegetative or by selfing. Cross-pollination largely depends on habitat conditions during the week-long flowering period.

Habitat preference, flowering time, and geographic distribution are important in keeping species distinct. Hybrids (especially in the stemless group) are common because flowers are compatible. A particular feature of compatibility is the chromosome number which is the same in most species (2n = 54). Even hybrids are often fertile. The relevence of this is to identification. It explains why it is difficult to write a key to these species and why, having a key, it is still sometimes difficult to identify them.

Leaves of violets are quite variable in shape; those of the stems (in the stemmed group), may be of a somewhat different shape from the basal ones. Leaves are alternate on the stems and presumably also on the rhizomes (underground stems) in the stemless species. Leaves have prominent stipules that may be toothed or fringed (see illustrations) and are useful to distinguish some species. (Stipules are the little leaf-like appendages at the base of each leaf.)

The showy flowers have five parts. The five sepals have eared bases (called auricles) and are persistent following flowering; the five petals are somewhat unequal, the two lateral ones often bearded (i.e., with a clump of hairs on the inner face). The lower petal is usually larger than the others and bears a spur or sac where nectar is produced. The stamens are fused together at the base around the pistil; the lowermost stamens bear appendages that extend into the spur of the lower petal. Nectary guides, which can be seen on the petals under ultra violet light, guide insects to the nectaries. To reach the nectar the visiting insect touches the stigma and also the appendages on the anthers. This causes pollen to drop on to the insect's back and is then carried to the stigma of another flower. The styles show considerable variation in shape, probably as an adaptation to pollination. Flowers are borne on stalks (peduncles) which have two small bracts near the middle.

Capsules contain small round seeds which vary in size and colour according to species. The seeds are very smooth and slippery and are later forcibly shot out of the capsule by the drying placenta which bears them.

Knowing this much, questions of all sorts then arise. If the showy flowers of the stemless species do not produce much seed, then how did they lose that ability? Is the cleistogamous flower an adaptation to ensure seed formation because of climatic conditions existing in spring? If so, what about the apparent abandoning of cross-pollination as a major means of reproduction? You could have a lot of fun exploring these problems.

The 15 violets of this region can be roughly classified into two groups: stemmed and stemless. The stemmed violets bear their flowers in the axils of stem leaves. In the stemless violets the flowers and the leaves arise from the tip of a thickened underground stem or rhizome; they also produce above ground stem branches called stolons which may appear during or after flowering. Often tufts of small leaves are borne at the stolon tips. Stemmed violets do not produce stolons. Let's look at the stemmed violets first because they are the easiest to recognize.

Stemmed violets

We have one yellow flowered, one multicoloured and three blue flowered. That's easy, isn't it? They are the Downy Yellow Violet (V. pubescens), the Canada Violet (V. canadensis), the American Dog Violet (V. labradorica ), the Hooked Violet (V. adunca), and the Long-spurred Violet (V. rostrata ).


Downy Yellow Violet | Violette pubescente
Viola pubescens Ait.

is from 10 to 40 cm tall and is soft hairy all over. There are 2-4 round leaves, 4 to 10 cm long, borne at the upper part of the plant; these are oval, short-pointed with flattened marginal teeth, and have a heart-shaped base. There may be a kidney-shaped basal leaf or none at all. Capsules are usually white-woolly but occasionally have only a few hairs. Yellow Violets are found chiefly in woods, occasionally in meadows (and in my garden where they come up all over the place; I guess they are happy there!). Flowering is from early May (or rarely the last week of April) through June. The Downy Yellow Violet is divisible into two varieties which may be distinguished as in the following key.

  1. Plants moderately to thickly hairy, bearing 1-2 flowering stems and 0-2 basal leaves
    Viola pubescens var. pubescens

    Plants hairless or almost so, bearing 3 or more flowering stems and 1-3 or more basal leaves
    V. pubescens var. scabriuscula Schwein ex T. & G.

The variety scabriuscula is often considered as a separate species by some authors; it is then given the common name Smooth Yellow Violet. (The scientific name is then V. eriocarpa Schw.).

Viola pubescens
Viola pubescens photo by Christine Hanrahan


Canada Violet | Violette du Canada
Viola canadensis L.

is one our most distinctive species. The plant is 20-40 cm tall and has numerous stems arising from a short rhizome. Upper leaves are 5 to 10 cm long, with lance-shaped stipules at the base and are more heart-shaped than the lower ones. Flowers have petals that are purple-tinged on the outside and white inside with a yellow eyespot and brownish purple veins near the base. This feature alone distinguishes it. Canada Violet is found in deciduous, usually maple woods having neutral or alkaline soils. Flowering is throughout May and June.

Note: Image courtesy of USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. Vol. 2: 560.



Canada Violet flowers are white, with pale mauve on the underside of the petals, and yellow in the centre of the flowers. Photo by Sandy Garland; inset by Christine Hanrahan


The remaining three stemmed violets are blue-flowered.

American Dog Violet | Violette decombante
Viola labradorica Schrank (synonym V. conspersa Reichenb.)

is common in fields and pastures. The plants may be only 2-4 cm tall in spring but become taller later in summer. Leaves are hairless. The basal leaves are round or kidney-shaped with rounded tips and fine rounded marginal teeth; the stem leaves are more heart-shaped and are 2-4 cm long with stipules that are spear-shaped and somewhat ragged or torn in the upper part. Flowers are up to 1 cm across, light blue with dark veins, the two lateral petals bearded (i.e. they bear a patch of hairs on the inside of the petal). The spur is short and blunt, perhaps 4-5 mm long. They flower in May and June.

[I am following Ballard (1994), who took up the earlier name V. labradorica Schrank for this violet.]


Flower of American Dog Violet. Photos by Christine Hanrahan

Back of flower showing blunt spur


Hooked Violet | Violette à éperon crochu
Viola adunca Sm.

Another very closely related species, the Hooked Violet, is not as common in our area as the American Dog Violet. The Hooked Violet has leaves that are densely short-hairy, ovate to nearly round with fine marginal teeth. The leaf base is straight across or very shallowly indented. The stipules are narrowly lance-shaped and vaguely spiny toothed. Petals may be light or dark blue. (In contrast, the American Dog Violet has leaves that are without hairs, more heart-shaped at the base; sepals are ciliate and petals are light blue.) Flowering of the Hooked Violet is in May and June. It is very common in Renfrew County and northwards and at Constance Bay and Gatineau Park.


Long-spurred Violet | Violette rostrée
Viola rostrata Pursh

is easily recognized by its long spur which may be 10-15 mm long (see illustration). They have quite long lance-shaped stipules which may be fringed above the middle. The leaves are very similar to those of the American Dog Violet but they have sharper tips. Flowers are light violet with darker veins forming a distinct eye. You may be able to find this species in woods near Bell's Corners, near Fallowfield and at Carleton Place. I have collected it near Westport; but it is common throughout all southern Ontario. Flowering is throughout May and possibly into early June.


Here is a key to the stemmed violets:

  1. Petals yellow or white and purple tinged; stipules entire
    Go to 2

    Petals blue or purple; stipules toothed like a comb
    Go to 3

  2. Petals yellow; stipules green
    Downy Yellow Violet, V. pubescens

    Petals white inside, usually purplish outside; stipules whitened
    Canada Violet, V. canadensis

  3. Lateral petals without hairs; spur 10 to 15 mm long; style tip straight
    Long-spurred Violet, V. rostrata

    Lateral petals bearing hairs; spur under 8 mm long; style tip bent
    Go to 4

  4. Leaves hairless with rounded marginal teeth. Leaf blades almost round, often pointed at the tips, the lower ones at least, heart-shaped at the base; stipules broadly spear-shaped, spiny toothed
    American Dog Violet, V. labradorica

    Leaves short-hairy, distinctly oval with blunt tips, the base vaguely heart-shaped, or merely straight across at the base; stipules linear, vaguely spiny toothed; northern species
    Hooked Violet, V. adunca

Stemless violets

The stemless violets are considered to be taxonomically quite difficult, but don't panic. They can be divided into blue ones and white ones.

WHITE STEMLESS: We have five, they are: the Sweet White Violet (V. blanda), the Large-leaved White Violet (V. incognita), the Lance-leaved Violet (V. lanceolata), the Kidney-leaved Violet (V. renifolia), and the Northern White Violet (V. macloskeyi ssp. pallens). Let's look at each one.


Sweet White Violet | Violette agréable
Viola blanda Willd.

has stolons present even on young plants which will distinguish it from the Kidney-leaved Violet (V. renifolia). The leaves always have some hairs which will separate it from the Northern White Violet (V. macloskeyi) which has glabrous leaves. The leaf and flower stalks are usually red-tinged. Leaves are broadly heart-shaped with a basal space that is so narrow that the lobes are almost overlapping. Petals are white, the 3 lower petals have brownish veins near the base. There is no beard of hairs on the inside of the lateral petals (unlike the Large-leaved White Violet). The Sweet White Violet is a species of wet cedar woods, swamps, wet deciduous woods, throughout the region. Flowering is throughout May and June.


Large-leaved White Violet | Violette méconnue
Viola incognita Brainerd

is rather sparse in this area. This violet produces thread-like stolons in summer. Leaves are hairless above but may have hairs along the petiole when they are young. The leaves are 2 to 4 cm wide at flowering and may enlarge to about 8 cm later in the season. Lateral petals are bearded. The cleistogamous or hidden flowers are borne on prostrate stalks and produce purplish capsules containing brown seeds. The Large-leaved White Violet is known from the Eardley Escarpment; Albert Dugal has it from his beloved Gloucester woods and it is known from near Ashton. That's about it. It apparently flowers in late May and fruiting specimens with cleistogamous flower stalks have been seen in July. The author of this species, Ezra Brainerd, was a great violet student who wrote several illustrated books and many papers on the topic. He also appropriately named his daughter, Viola!

Note: Image courtesy of USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. Vol. 2: 556.


Lance-leaved Violet | Violette lancéolée
Viola lanceolata L.

is immediately recognizable by its lance-shaped leaves (see illustration) and by the stolons which appear after flowering and become longer later in the season. Mature leaf blades are 2.5 to 12 cm long and up to 2.5 cm wide. The flowers are white with purple veins and extend as high as the leaves or beyond. The cleistogamous flowers are borne on long stalks or on short stalks arising from the stolen axils. Our records are from the shores of the Ottawa River from Ayhner, the mouth of the Gatineau River, Quyon, Calumet, Pontiac Bay, Bristol, Rapides-des-Chats, and Buckham's Bay. Early in the season when the river is in flood, it may be impossible to find this species. Flowering is from early June until July; fruiting up to October.


Viola lanceolata, photographed by Christine Hanrahan


Kidney-leaved Violet | Violette réniforme
Viola renifolia A. Gray

is rather sparse in our region. As I pointed out earlier the lack of stolons distinguishes this species from the Sweet White Violet (V. blandd). The leaves are widely spreading, kidney-shaped to round with heart-shaped bases. Flowers are white with purple stripes, the lateral petals without beards. Both the sepals and sepal ears (auricles) have ciliate hairs. This is a northern species and occurs sporadically in the region (Constance Bay, Britannia (at one time)). It grows in pine woods and white cedar woods. Flowering is in May and June.


Northern White Violet | Violette pâle
Viola macloskeyi F.E. Lloyd ssp. pallens (Banks ex DC.) M.S. Baker

can be confused with the Sweet White Violet (V. blanda) but differs from it by having completely hairless leaves and margins with rounded teeth or no teeth. Lateral petals have a small tuft of hairs on the inside. The cleistogamous capsules are green and have black seeds and are borne on erect or arching stalks. This is a common violet found in swampy woods, coniferous woods and water margins. It flowers throughout May into early June.

Note: Image courtesy of USDA-NRCS PLANTS Database / USDA NRCS. Wetland flora: Field office illustrated guide to plant species. USDA Natural Resources Conservation Service.


Here is a key to the above stemless white violets:

  1. Stolons (a stem branch creeping on the surface of the ground) mostly lacking; leaves kidney-shaped (reniform)
    Kidney-shaped Violet, V. renifolia

    Stolons present; leaves not kidney-shaped
    Go to 2

  2. Leaves twice as long as wide, not heart-shaped at the base (see illustration)
    Lance-leafed Violet, V. lanceolata

    Leaves as wide as or wider than long, heart-shaped at the base
    Go to 3

  3. Lateral petals without a beard (no hairy area on the inside of the lateral petals)
    Sweet White Violet, V. blanda

    Lateral petals bearded
    Go to 4

  4. Petioles and lower leaf-surfaces densely hairy; cleistogamous (hidden) flowers on prostrate stalks
    Large-leafed White Violet, V. incognita

    Petioles and lower leaf-surfaces hairless or nearly so; cleistogamous flowers on erect stalks
    Northern White Violet, V. macloskeyi ssp. pallens

STEMLESS BLUE VIOLETS: We used to have a lot of difficulty with this group of species, but recently they were revised by Landon E. McKinney (1992) who reduced the number of species. The Woolly Blue (V. sororia) now encompasses many "species" which were difficult to key out using such characteristics as whether or not the hairs on the petals were club-shaped or straight (see illustration), and so on. Now, ideally, all you have to do is accept McKinney's treatment and call all these "microspecies" V. sororia. However, life isn't that simple. More recently, Ballard (1994), in writing up the violets of Michigan considered one of the segregates of sororia, V. nephrophylla Greene, as a separate species more closely allied to V. cucullata than to V. sororia. I am including V. nephrophylla Greene as a separate species here.

We have five stemless blue violets in our region, the Marsh Blue Violet (V. cucullata), the Northern Bog Violet (V. nephrophylla), the Northern Downy Violet (V. sagittata), the Great Spurred Violet (V. selkirkii), and the Woolly Blue Violet (V. sororia). Let's look at them one by one.


Marsh Blue Violet | Violette cucullée
Viola cucullata Ait.

This is the floral emblem of New Brunswick. Its occurrence in predominently wet habitats - swamps, wet meadows, bogs and wet woods - almost distinguishes it. Its rhizome may be branched causing the plant to form colonies. Leaves are oval to kidney-shaped, with acute tips. The lateral petals are bearded with club-shaped hairs; the spurred petal is beardless and shorter than the laterals. The sepals are prominently eared (auricles) at the base. Both showy and hidden flowers are borne on erect or nearly erect stalks or peduncles. Flowering and fruiting is from April to July. Marsh Blue Violet occurs in the Maritimes, western Quebec and throughout southern Ontario as far north as the Thunder Bay region. It ranges as far south as northern Georgia and west to Iowa.


Northern Bog Violet | Violette néphrophylle
Viola nephrophylla Greene

Superficially this species is similar to the Marsh Blue Violet (V. cucullata) from which it differs in having the spurred petal bearded with threadlike hairs, and its sepals have very short auricles. It is often confused with the Woolly Blue (V. sororia) from which it differs by its green cleistogamous capsules which are borne on erect stalks (peduncles) and by its olive-black seeds. The foliage is hairless. The floral stalks are longer than the leaf stalks, so the flowers overtop the leaves. The habitat is also very critical. The Northern Bog Violet occurs in open alkaline habitats. It is common on the "Burnt Lands" near Almonte. This species also flowers in May.

Note: Image courtesy of USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. Vol. 2: 551.


Northern Downy Violet
Viola sagittata Ait. var. ovata (Nutt.) Torr. & Gray

(I don't know the French common name). You should not have any difficulty with this violet because it only occurs on the sandhills of Constance Bay in our region. In other parts of its range it occurs in dry habitats such as fields and slopes. Northern Downy Violet occurs scattered throughout southern Ontario, in southwestern Quebec and in southern Nova Scotia. In the U.S. it is found as far south as the Carolinas and west to Iowa. McKinney divided the species into two varieties, of which we only have var. ovata. This plant has oval leaves that are flat across the base and are densely short hairy. Petals are dark blue-violet; the lateral petals are bearded. Sepals are oval to lance-shaped with sharp tips. Its seeds are beige to bronze coloured. Flowering is April and May. (This species used to be called V. fimbriatula Sm. but an earlier name is now being used.)

Note: Image courtesy of USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. Vol. 2: 552.


Viola sagittata photographed at the Constance Bay sandhills by Christine Hanrahan. Below left: "beards" on side petals. Below right: sharply pointed sepals


Selkirk's Violet | Violette de Selkirk
Viola selkirkii Pursh

is rather sparse in this region. It was collected near Chelsea in 1906 and I collected it three times in Gatineau Park in 1967 and 1968. On the Ontario side of the river we have old collections from Ottawa, Carleton Place, Moose Creek, Carp, and recently Albert Dugal collected it from South Gloucester.

Selkirk's Violet has slender underground stems but no stolons. Leaves are hairless below and slightly hairy above. The leaf blades are 1.5-4.5 cm broad, broadly oval with a heart-shaped base; the basal lobes often obscure the gap between them. Flowers are pale violet, about 2 cm in diameter. The petals are beardless and the spur is 5-7 mm long, as long as the blade of the spurred petal. Cleistogamous flowers are borne on ascending stalks. The capsule is almost round and purple-dotted. This is a plant of cool, rich woods and ravines, often in calcareous regions. It flowers from mid-April (but not in 1996!) throughout May but is visible and recognizable throughout the summer. (This species is also known as the Great Spurred Violet, not to be confused with the Long-spurred Violet, Viola rostratd).

Note: Image courtesy of USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. Vol. 2: 555.


Woolly Blue Violet | Violette parente
Viola sororia Willd.

has oval leaves having a heart-shaped base and marginal teeth which are either round or sharp-toothed. The blue flowers are overtopped by the leaves. The spurred petal has no hairs within, or just a few. Sepals are blunt with weakly developed basal ears. Capsules are purple-flecked and are borne on prostrate stalks. Viola sororia occurs in open woods and waste ground throughout southern and eastern Ontario, southern Quebec and New Brunswick, and is very common. Flowering is through April, May and well into June, occasionally again in September, dependent upon the weather.


These five stemless blue species can be separated with the following key (adapted and simplified from Ballard)

  1. Leaves strongly heart-shaped with a narrow sinus, the basal lobes commonly overlapping; upper surface of leaf blades with erect white hairs; stipules less than 6 mm long, united to the leafstalks about half their length; petals beardless; spur 5-7 mm long
    Selkirk's Violet, V. selkirkii

    1. Leaves tapering or heart-shaped at the base, the basal lobes not overlapping; stipules over 7 mm long, never united to the leaf stalks
    Go to 2

  2. Most or all leaf blades distinctly longer than broad, sparsely to densely short hairy; sepals usually long-tapering to a sharply acute apex; lateral petals bearded; Constance Bay only
    Northern Downy Violet, V. sagittata

    Most or all leaf blades nearly as broad as long, or broader
    Go to 3

  3. Lateral petals bearded within by short, knob-shaped hairs; spurred petal hairless within; flowers commonly overtopping leaves; sepals long-tapering, sharply acute at apex, with well-developed, eared bases
    Marsh Blue Violet, V. cucullata

    Lateral (and often spurred) petals bearded within by long, thread-like hairs; sepals oblong, lance-shaped to oval, blunt to rounded at the tip, with inconspicuous eared bases
    Go to 4

  4. Flowers commonly overtopping leaves (especially in early flowering); foliage essentially hairless; largest leaf blades mostly blunt to rounded at the apex, straight across to nearly heart-shaped at the base, with flattened teeth along the margins; spurred petal densely bearded; plants of wet, alkaline, open habitats
    Northern Bog Violet, V. nephrophylla

    Leaves commonly overtopping flowers; foliage commonly moderately to densely long hairy; largest leaf blades acute to abruptly pointed at the tip, strongly heart-shaped at the base, sharply toothed along the margins; spurred petal scantily bearded; plants of moist to dry forest habitats
    Woolly Blue Violet, V. sororia

A parting word. Remember that hybrids between native species do occur. Be alert to possible hybrids between those species that are found in the same habitat.

I hope you have fun trying to identify violets as I do. I recall a man who rarely steps out of his office and who accompanied me on a walk through the woods. On finding a violet, he asked, "What's this purple thing?" Incredible!

References

  • Ballard, Harvey E., Jr. 1994. Violets of Michigan. Michigan Botanist 33 (4): 131-199.
  • Gillett, John M. and David J. White. 1978. Checklist of vascular plants of the Ottawa-Hull region, Canada/Liste des plantes vasculaires de la région d'Ottawa-Hull, Canada. 155 pp. + map.
  • McKinney, L.E. Unpublished, undated note: A brief synopsis of a forthcoming revision of the acaulescent blue violets of North America. 8 p.
  • McKinney, L. E. 1992. A taxonomic revision of the acaulescent blue violets (Viola) of North America. Kentucky State Nature Preserves Commission, 407 Broadway, Frankfort, KY 40601, USA. 60 p.

Illustrations are mostly by Marcel Jomphe, but the two habit sketches are by Sally Gadd, done some years ago.


This page was revised on 19 May 2009
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