Obtusifolius is from the Latin obtundo meaning blunt and folium meaning leaf and refers to rounded tips of the leaves
Broadleaf Dock refers to the broad leaves of this species. Dock is from the Old English docce meaning a coarse weedy herb.
Other names:
Broad dock.
Summary:
A erect plant with an annual rosette of large, broad leaves with indented bases and long flowering stems with compact seed heads and a perennial, carrot like rootstock. It flowers from September to January and has fruit with spined wings and 3 warts or tubercles.
Description:
Cotyledons:
Two. 10 to 15 mm long overall. Tip rounded to pointed. Sides parallel to convex. Base tapered. Surface hairless. Petiole shorter than blade and merging with it. The seedling has a very short hypocotyl and no epicotyl.
First Leaves:
The leaves develop singly, the first having a blade 12 to 18 mm long with a petiole 4 to 8 mm long which tends to elongate at the leaf ages. Later leaves become more elongated and the margin slightly wavy.
Leaves:
Forms a rosette at the base and has alternate leaves on the stem.
Stipules - Membranous sheath(ochrea), 25-55 mm long, reddish, translucent, obviously veined, ragged, at the base of the petiole.
Petiole - 150-250 mm long on basal leaves.
Blade - Of rosette leaves, bluish green, oblong to egg shaped, to 30-300 mm long by 15-140 mm wide, smooth, rounded tip, usually have a notched base, sometimes with round teeth on the edges and crimped to wavy on the edges. Hairless or with short hairs along the veins on the under surface.
Stem leaves - Alternate. Lower stem leaves are 200-250 mm long with a long petiole,30-50 mm long, with a rounded tip and base. Towards the top of the stem they are much reduced in size. Hairless or carry a few very short hairs on the under side of the veins. The stem leaves are shorter and much narrower than the rosette leaves with a base angle of approximately 45 degrees, and have a distinctly wavy margin.
Stems:
The stems are solid and pithy, stout, 600-1500 mm tall, carry a few very small hairs located principally below the node, and have dark striations, rough to touch or smooth. The stem cross section is irregularly polygonal with longitudinal ridges while small stems tend to be circular and fluted. The stems are branched from the base and along their length. Where branching occurs the main stem and its branch frequently form a shallow 'V' at the node. Several stems usually grow from an established rootstock.
Flower stem -
Flower head:
In ring-like, several-many flowered clusters that are close together on curved stalks so the fruit hide the stem on the upper part of the curved, diverging branches forming an open, erect panicle. No leaves near the top and may be a few small leaves under the clusters near the base of the panicle.
Flowers:
Male or female, 2-3 mm in diameter, with 3 green to reddish petal-like sepals.
Bracts - Ochreola, 2-4 mm long, brown, translucent.
Ovary - 3 styles with large, tufted stigmas.
Perianth - 6 segments, 3 inner ones enlarged and close over the fruit.
Stamens - 6.
Anthers -
Fruit:
Achene enclosed by 3 inner perianth segments or valves. Valves 4-6 mm long, egg shaped to triangular, acute to obtuse tip, with about 2-3 pointed teeth around the middle of each side. One of the three valves has a large wart(tubercle). Each achene on curved, slender stalk, 8-15 mm long that holds it away from the stem. Initially green-brown and becoming dark brown with age.
Seeds:
Triangular pyramid, brown nut, 2.5-3.2 mm long.
Roots:
Stout, carrot like rootstock comprised of a short, 30-50 mm long, underground stem and a stout, often branched taproot, to 300 mm long and feeder roots to 2000 mm deep.
Key Characters:
Perennials.
Leaves not hastate, base tapering or truncate, not lobed.
Fruiting perianth inconspicuous.
Perianth lobes 6, the inner 3 larger than the outer, scarious-reticulate and obtuse, at least 1 lobe with a conspicuous swollen tubercle in the lower half, margin toothed below.
Flowers bisexual, rarely polygamous.
Flower clusters, many flowered, approximate, without floral leaves except to the lowest ones.
Fruiting valves with 3-4 hooked or straight teeth along the margins, apex of valve broadly acuminate or acute.
Fruiting pedicels 8-12 mm long.
From J.M. Black, N.T. Burbidge and G. Perry.
Biology:
Life cycle:
Annual top and perennial rootstock. Seeds germinate mainly in autumn and spring and form a rosette and rootstock over winter. Around the 5 leaf stage the upper part of the root contracts pulling the crown deeper into the soil. Some may produce flowering stems in the summer. Top growth dies over summer leaving the perennial rootstock in the soil. Most spring germinating seedlings die. Shoots emerge from rootstocks in autumn and quickly form a large rosette that shades and crowds neighbouring plants. Flower stems emerge in late spring to early summer and form seed over summer. The stems and top growth dies off in summer or autumn though some rosette leaves may persist in summer moist areas.
Physiology:
There are three phases of growth of carbohydrate storage;
1) a rapid decrease in carbohydrate stores as the shoots emerge in autumn or after cutting,
2) Build up of stored carbohydrate in the roots after the shoots reach 300 mm tall and continuing until the end of flowering,
3) Constant level of stored carbohydrate as the seeds mature and flowering stem wither.
Reproduction:
By seed and perennial rootstock.
Flowering times:
November to January in SA.
September in Perth.
Seed Biology and Germination:
Exposure to light, alternating temperatures, stratification(chilling of moist seed) and nitrate increases germination.
Some seed is dormant.
Some seed may last for many years in the soil.
Vegetative Propagules:
Perennial rootstock.
Hybrids:
Forms hybrids with Curled Dock (Rumex crispus).
Allelopathy:
Population Dynamics and Dispersal:
The pithy wart on the fruit assist flotation for dispersal by water.
The teeth on the fruit entangles in wool, fur and fibrous material the assist spread by animals and man.
Seed consumed by animals is passed in a viable condition.
Rootstocks readily re shoot after being broken by and/or moved by cultivation.
It is also spread as a contaminant of grain and hay.
Autumn germinating seedling usually have a higher survival rate than spring germinating seedlings. Seedlings may produce rootstocks capable of withstanding summer drought in 30-50 days. Seedlings are very sensitive to competition and usually only survive in relatively bare areas. However, once established they are very competitive. They often rapidly colonise areas that have been denuded.
Produces up to 60,000 seeds per plant.
Origin and History:
Europe. Asia.
Distribution:
ACT, NSW, NT, QLD, SA, TAS, VIC, WA.
Found in all parts of Tasmania and is one of the two major dock species. Courtesy Australia's Virtual Herbarium
Habitats:
Damp situations.
Climate:
Temperate. Mediterranean. Cool to mildly warm temperate. Sub tropical areas.
Soil:
More abundant on fertile loams and clays.
Plant Associations:
Significance:
Hybrids between Broad-leaved and Curled Dock occur.
Beneficial:
Used in herbal medicine for rubbing on skin to neutralise stinging nettle and other skin irritations.
Detrimental:
Weed of lucerne, orchards, pastures, roadsides, drains, streams, swamps, grasslands, woodlands, hops, irrigated crops and disturbed areas.
In Tasmania, it occurs frequently in pasture during the establishment stages and also in pasture where poor drainage or water-logging present problems at some time during the year. It is very common on roadsides and in waste areas and can be a serious pest in ditches or drainage channels. In crops it is often strongly competitive.
Toxicity:
May contain potentially toxic amounts of oxalate that could lead to oxalate poisoning but it is rarely a problem in the field.
Legislation:
Noxious weed of TAS and WA.
Management and Control:
Seedlings less than 6 weeks old can usually be controlled by cultivation. Repeated cultivation over summer are required to control rootstocks.
Mowing and slashing are ineffective.
Some selective control in legume based pastures can be achieved by using glyphosate in a blanket wiper in late spring.
Thresholds:
5-10 plants/m2 can reduce herbage yields of pasture by 30%.
Eradication strategies:
Remove isolated plants by cutting their roots at least 200 mm below ground level.
Apply 800 mL/ha glyphosate(450g/L) plus 40 g/ha Logran plus 5 g/ha Ally plus 1 L of Pulse Penetrant per 400 L of spray mix, 2-3 weeks after the break. Cultivate 5 days later and plant wheat.
OR Apply 1000 mL/ha glyphosate(450g/L) plus 500 mL/ha Dicamba(200g/L) plus 1 L of Pulse Penetrant per 400 L of spray mix, 2-3 weeks after the break and cultivate 5 days later and plant oats or barley.
6-8 weeks after planting apply 5 g/ha of Ally in wheat and barley crops or 750 mL/ha of dicamba amine in oat crops.
In following break crops use triazine or urea herbicides to reduce the establishment of dock for dormant seed.
In following clover pastures, Spray Graze with 750 mL/ha of 2,4-D amine(500g/L) 6-8 weeks after the break of the season to prevent seedlings establishing. Repeat this annually for at least 5 years.
In bushland, individual plants may be wiped with a mixture of 1 L glyphosate(450g/L) in 2 L water. Small infestations may be sprayed with 0.5g chlorsulfuron(600g/kg) plus 100 mL Tordon 75-D in 10 L of water in winter. This mix controls existing plants and has residual activity to control seedlings about a year. Some seed will remain viable in the soil for 20 years.
Blanket wiping with 1 L glyphosate(450g/L) plus 20 g chlorsulfuron(750g/kg) plus 2 L water in spring is reasonably selective in pastures. This mix may be applied manually to individual plants.
2 L/ha glyphosate(450g/L) can be used selectively in some seasons when dock is green in autumn or summer and the annuals are not. Metsulfuron is also effective.
Grazing, mowing and cultivation usually lead to greater stands.
Plant tall growing perennial species to increase the levels of shade and help reduce re-invasion.
Herbicide resistance:
Biological Control:
A number of biocontrol agents are under investigation and some have been released in Australia.
Related plants:
Bladder Dock (Rumex vesicarius)
Clustered Dock (Rumex conglomeratus)
Curled Dock (Rumex crispus) is a tall plant up to 1.5 m tall with pointed oval leaves that are 4-24 cm long. The leafless inflorescence has densely clustered flowers and fruits. The fruit valves are reddish brown, swollen in the centre, with smooth margins and lacking teeth.
Fiddle Dock (Rumex pulcher) is a plant to 50 cm tall with rounded oblong leaves, the basal ones sometimes slightly constricted in the middle and appearing fiddle-shaped. The leaves are 4-15 cm long. The leafy inflorescence has distant whorls of flowers and fruits. The fruit valves are brown, swollen and warty in the centre and the margin has prominent stiff teeth.
Mud Dock (Rumex bidens)
Rambling Dock (Rumex sagittatus)
Shiny Dock (Rumex crystallinus)
Sorrel (Rumex acetosella)
Swamp Dock (Rumex brownii)
Wiry Dock (Rumex dumosus)
Plants of similar appearance:
Spiny Emex (Emex australis) looks similar especially when young.
References:
Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P209. Diagram of seed.
Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P281. Diagram of seed.
Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P153.
Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P202. Diagram of seed.
Hyde-Wyatt, B.H. and Morris, D.I. (1975). Tasmanian weed handbook. (Tasmanian Department of Agriculture, Hobart, Tasmania). P56-57. Diagrams.
Hyde-Wyatt, B.H. and Morris, D.I. (1980) The Noxious and Secondary Weeds of Tasmania. (Tasmanian Department of Agriculture, Hobart, Tasmania). P64-65. Diagrams.
Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).
Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P116.
Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). P547-552. Diagram. Photos.
Acknowledgments:
Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.
