kingdom Plantae - plants »  divisio Magnoliophyta - flowering plants »  class Rosopsida - eudicots » order Malpighiales »  family Violaceae »  tribus Violeae > genus Viola > Viola sect. Viola  L. > Viola subsect. Rostratae Kupffer    

Viola riviniana Rchb. - Common Dog-violet

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Synon.: Viola sylvestris subsp. riviniana (Rchb.) Čelak.; Viola sylvatica var. macrantha Fries

Common names: common dog violet; dog violet; wood violet; skogsviol; Viola di Rivinus;  rivinus' Veilchen; violeta de monte; violette de Rivin

Description: Hemicryptophyte. Rhizomatous, caulescent perennial. Rhizome vertical, normally branching at (or occasionally below) the soil surface, covered with numerous brown stipules, with a terminal leaf rosette. Rosette leaves 3–5; stipules subulate, 8–12.5 mm, brown, with 5–8 coarse fimbriae which are shorter than the maximum width of the entire part of the stipule; petiole to 12 cm, glabrous or sometimes puberulent; blade ovate, broadly ovate or reniform, 25–45 × 22–38 mm, 1–1.4 times as long as wide, pure green, with rather numerous short hairs on the upper surface, glabrous or with few hairs along the veins on the lower surface; margin crenate with 15–20 obtuse teeth or near the base with forward-pointing teeth; base cordate to deeply cordate; apex acute or obtuse. Aerial stems developing before chasmogamous flowering, erect or ascending, to 30 cm, glabrous, papillose, slightly hairy at the nodes or sometimes puberulent throughout. Stem leaves 3–9; stipules subulate, 6–11 mm, green but turning brown with age, with fimbriae shorter than the maximum width of the entire part of the stipules; petiole to 6 cm, decreasing in length towards the top of the stem, glabrous or sometimes puberulent; blade of middle stem leaves ovate to broadly ovate, 30–50 × 30–42 mm, 1–1.3 times as long as wide, pure green, with rather numerous short hairs on the upper surface, glabrous or with few hairs along the veins on the lower surface; margin crenate with 15–20 obtuse teeth or near the base with a forward-pointing tooth; base cordate to deeply cordate; apex acute.

Chasmogamous flowers scentless, from the middle or upper part of the aerial stems. Pedicels glabrous or sometimes puberulent, to 10 cm, longer than the subtending leaves; bracteoles subulate, in the upper half of the pedicel. Sepals lanceolate, acute, upper ones 5–8 × 1.1–1.7 mm, lateral ones 5.5–8.5 × 1.7–2.5 mm (in both cases excluding the appendage); appendage suborbicular to truncate, on upper sepals 0.8–1.8 × 0.6–1.3 mm, on lateral ones 1.1–2.5 × 1.3–2 mm, all 0.15–0.35 times as long as the rest of the sepal. Corolla 17–25 × 17–25 mm, 0.9–1.1 times as high as wide, flat in front view. Petals violet, whitish at the base, clearly overlapping; upper petals recurved, broadly obovate, 13–18 × 6–9 mm, 1.8–2.4 times as long as wide; lateral petals narrowly obovate, 14–18 × 6–9 mm, 1.9–2.4 times as long as wide, with hyaline hairs at the throat; spurred petal slightly concave, 13–17 × 7.5–10 mm excluding the spur, 1.4–2 times as long as wide, with 2–5 distinct veins at the throat; spur white or rarely violet, thick, straight or upcurved, blunt, 5–7 × 3–4 mm, 1.5–2 times as long as wide, 3–7 times as long as the sepal appendages. Style papillose near the tip.

Cleistogamous flowers 3–4 mm, lower sepal appendages longer than the upper ones, 0.12–0.2 mm. Capsule ovoid, trigonous, obtuse, 8–12 mm, glabrous, explosive. Seeds ovoid, 1.8–2.1 × 1.1–1.3 mm, pale to light brown; elaiosome small. – Early spring to mid-spring, occasionally autumn (chasmogamous flowers), mid-spring to mid-summer (cleistogamous flowers).

2n=35–40 (F A), c. 40 (F EH), 40 (D Sjæ). – [2n=40]

Distributional Range: Native Africa NORTHERN AFRICA: Algeria, Morocco, Tunisia Asia-Temperate WESTERN ASIA: Lebanon Europe  NORTHERN EUROPE: Denmark, Faroe Islands, Finland, Iceland, Ireland, Norway, Svalbard and Jan Mayen, Sweden, United Kingdom MIDDLE EUROPE: Austria, Belgium, Czechoslovakia, Germany, Hungary, Luxembourg, Netherlands, Poland, Switzerland EASTERN EUROPE: Belarus, Estonia, Latvia, Lithuania, Russian Federation-European part, [European part] Ukraine SOUTHEASTERN EUROPE: Albania, Bulgaria, Former Yugoslavia, Greece, Italy (incl. Sardinia, Sicily), Romania SOUTHWESTERN EUROPE: Andorra, France (incl. Corsica), Portugal, Spain

Habitat:  Moist to moderately dry, modestly to very nutrient-rich soil in woodland; towards the north slightly basiphilous. – Glades in deciduous woodland and spruce forest, oak scrub, calcareous pine forest, in the mountains in south-facing scree; occasionally in dry grassland or in shady, mossy forest, in the latter case usually not flowering.

Taxonomy: Viola riviniana is a tetraploid based on x=10 (a number originated from ancient polyploidization of taxa with x=5). It appears to be an allopolyploid with V. reichenbachiana as one parent; the other one, an unknown taxon no longer occurring in Europe, was also involved in the origin of V. canina

Variation. Viola riviniana is fairly variable in leaf shape and size, outline of the corolla, petal colour and shape and size of the spur. The spur is typically white, but may be as dark as the rest of the corolla. Usually the plants have scattered hairs only on the upper surface of the leaves, but variants which are densely short-hairy also on the stems and peduncles occur; such plants can be reminiscent of V. rupestris which, however, has much shorter hairs. Besides, height and vigour vary according to the habitat conditions; specimens from exposed sites tend to be smaller and more compact than those growing in shady places.

A variant with purple leaves and hairy stems is sometimes cultivated (incorrectly referred to the NE American V. labradorica Schrank).

Hybridization: Hybridization. Hybrids of Viola riviniana are known with V. canina, V. elatior, V. mirabilis, V. pumila, V. reichenbachiana, V. rupestris ; both subspecies, V. stagnina  and V. uliginosa

References:

1. Aldén, B., S. Ryman, & M. Hjertson. 2012. Svensk Kulturväxtdatabas, SKUD (Swedish Cultivated and Utility Plants Database; online resource) URL: www.skud.info

2. Botanical Society of the British Isles. BSBI taxon database (on-line resource).

3. Castroviejo, S. et al., eds. 1989-. Flora iberica: plantas vasculares de la Peninsula Iberica e Islas Baleares.

4. Czerepanov, S. K. 1995. Vascular plants of Russia and adjacent states (the former USSR) Cambridge University Press.

5. Fennane, M. & M. I. Tattou. 1998. Catalogue des plantes vasculaires rares, menacées ou endémiques du Maroc. Bocconea 8:189.

6. Fernández Casado, A. 1984. Estudios sobre el género Viola L. en la península Ibérica I. Cariología. Fontqueria 5:25.

7. George, A. S., ed. 1980-. Flora of Australia.

8. Huxley, A., ed. 1992. The new Royal Horticultural Society dictionary of gardening

9. Jahandiez, E. & R. Maire. 1931-1941. Catalogue des plantes du Maroc. Note: = Viola sylvestris subsp. riviniana (Rchb.) Tour.

10. Komarov, V. L. et al., eds. 1934-1964. Flora SSSR.

11. Liberty Hyde Bailey Hortorium. 1976. Hortus third.

12. Mouterde, P. 1966-. Nouvelle flore du Liban et de la Syrie.

13. Pignatti, S. 1982. Flora d'Italia.

14. Pottier-Alapetite, G. 1979-1981. Flore de la Tunisie: Angiospermes-Dicotyledones. Note: = Viola sylvestris subsp. riviniana (Rchb.) Tour.

15. Quézel, P. & S. Santa. 1962-1963. Nouvelle flore de l'Algerie. Note: = Viola sylvestris subsp. riviniana (Rchb.) Tour.

16. Tutin, T. G. et al., eds. 1964-1980. Flora europaea.