Viola arvensis Murray
Synonym - Viola tricolor.
Arvensis is from the Latin arvum meaning cultivated field and refers to the plants association with cultivation.
Other names:Field Violet (USA)
Wild Pansy (USA)
Summary:A low lying, hairy annual or biennial with lobed leaves, large divided stipules and cream flowers with a yellow-orange blotch on one petal. The flowers are carried on long stalks.
Two, oval, 3-6 mm long x 3-4 mm wide. Tip rounded. Sides convex. Base tapered to squarish. Surface hairless. Petiole shorter than blade. The seedling has a very short hypocotyl and no epicotyl.
First leaves: Arise singly, the first being 4 to 6 mm long with a short petiole. The early leaves are hairless and have a terminal and one lateral lobe on each side. As the plant grows the leaves become larger and more lobed.
Leaves: Alternate and form a rosette.
Stipules - Half as long to longer than the leaves, up to 40 mm long, deeply divided into narrow lobes with the end node leaf like.
Petiole - 10-20 mm long.
Blade - 10-35 mm long x 5-15 mm wide. Broadly egg shaped to elliptical, with a terminal and 2 or 3(5) lateral lobes per side or with rounded teeth. Obtuse to acute tip. Squarish to tapered base.
Stem leaves - Two forms occur; In one the stem leaves are an elongated oval, lobed, and usually hairless. In the other the leaves are elongated with tooth-like lobes which tend to be forward directed, and are more or less hairy particularly towards the margin and on the veins on the underside. However both oval and elongated leaves may occur on the same plant. Surface hairless or hairy especially on the veins or under surface.
Stems: Drooping to erect, 200-300 mm tall, hollow, angular with fine longitudinal ridges, and may carry short hairs. May be branched. Usually 200-300 mm long.
Flower stems (scapes) 30-80 mm long.
Flower head:The flowers are axillary and carried on long stalks (pedicels) as long as the leaf and twice as long when in fruit. Bracteoles just below the flower.
Flowers: Cream, with yellow orange to purple markings. 10 mm in diameter and length.
Sepals - Narrowly egg shaped with a pointed tip and basal appendages. Lower sepals 6-10 mm long. Upper sepals slightly shorter. Persistent and enclose the seed capsule after flowering.
Petals - 5 petals; 5-10 mm long, the upper 4 petals are cream in colour and the bottom petal cream with a yellow to orange centre, sometimes tinged with violet and with a short spur. Shorter than or equal to the sepals.
Fruit:Triangular pyramid, 3 valved capsule, 5-9 mm long, slightly longer than the calyx. Usually ejects seeds explosively.
Seeds:Seeds have an appendage (aril).
Produces around 2500 seeds per plant.
Seeds may persist in the soil for some years.
1288 have shown dormancy cycles and conditional dormancy cycles for the seed.
Roots:Fibrous. Often smell like wintergreen when crushed.
Key Characters:Annual or biennial pubescent herb.
Stipules to 40 mm long and green.
Stipules pinnately divided into linear lobes.
Lower petal broad-cuneate.
Fruit a 3 valved capsule.
Annual or biennial. Seeds germinate mainly in spring with a minor germination in autumn.
Physiology:Chromosome number 2n=34.
Flowering times:Summer in NSW.
Seed Biology and Germination:Produces around 2500 seeds/plant.
Seed germinates at any time of the year in California.
Best germination from depths of 0.5 to 1 cm.
Often has a staggered germination and seedlings may establish after the crop is planted.
Population Dynamics and Dispersal:
Spread by seed.
Seed often dispersed by ants.
Origin and History:Native to Europe. Northern Africa. Western Asia.
Distribution:ACT, NSW, TAS, VIC.
Common in many parts of the north and south of Tasmania.
Courtesy Australia's Virtual Herbarium.
Habitats:Wet areas, pastures, disturbed moist sites.
Detrimental:Weed of cereals, corn, crops, pastures, soybeans, wetlands and disturbed areas.
Toxicity:Seed may be toxic (Filmer, 2008). Not recorded as toxic in the field.
Management and Control:Glyphosate provides good control.
Post emergence atrazine at 1kg a.i./ha provides suppression.
Imazethapyr provides suppression.
Bromoxynil provides about 70% control.
Dichlorprop + 2,4-D and some of the sulfonylureas appear to give the best post emergence selective control.
Relatively tolerant to normal rates of 2,4-D and dicamba.
Post emergence herbicides have often given variable control.
Tillage provides good control of emerged plants.
Prevent seed set.
Manually remove isolated plants.
Herbicide resistance:Biological Control:
Ivyleaf Violet (Viola hederacea)
Common Violet (Viola odorata)
Common Dog Violet (Viola riviniana).
Plants of similar appearance:The lobed leaf of the seedling is not unlike that of Speedwell, Stagger-weed, and Dead Nettle, but Field Pansy is easy to separate from the seedlings of these species because it has leaves that are not paired, and it grows initially as a rosette.
References:Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P258.
Harden, Gwen J. (1991). Flora of NSW. (Royal Botanic Gardens, Sydney). Volume . P437. Diagram.
Hyde-Wyatt, B.H. and Morris, D.I. (1975). Tasmanian weed handbook. (Tasmanian Department of Agriculture, Hobart, Tasmania). P84-85. Diagrams.
Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).
Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #1271.1.
Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.