Docks

Images above: Upper Left: Curly dock seedling (Scott Morris, Cornell University). Upper Right: Curly dock rosette (Antonio DiTommaso, Cornell University). Bottom: Curly dock fruit (Scott Morris, Cornell University).

Image above: Curly dock plant (left) and broadleaf dock plant (right) (Scott Morris, Cornell University).

Images above: Left: Broadleaf dock seedling (Antonio DiTommaso, Cornell University) Right: Broadleaf dock rosette (Antonio DiTommaso, Cornell University)

Identification

Other common names:

• Broadleaf dock:  bitter dock, blunt-leaved dock, red-veined dock, broad-leaved dock, celery seed
• Curly dock:  yellow dock, sour dock, narrow-leaved dock, curled dock

Family:  buckwheat family, Polygonaceae

Habit:  Erect, taprooted, perennial herbs with basal rosettes of large leaves.

Description:  Young leaves of seedlings develop basal rosettes.  Leaf edges unfurl outwards from underneath the leaf. 

• Broadleaf dock:  Cotyledons are egg shaped 0.4-0.7” (1-1.8 cm) long by 0.14-0.25” (0.26-0.64 cm) wide and gritty on both sides.  First true leaves are ovate to oblong shaped.  All subsequent young leaves are oblong and wavy-edged; they have heart-shaped bases, white hairs beneath their stalks and midveins, and possible red flecking on the veins and blade.
• Curly dock:  Thumb shaped cotyledons are hairless, gritty to the touch, and 0.3-0.6” (0.76-1.5 cm) long by 0.1-0.2” (0.25-0.51 cm) wide with fleshy, possibly red-flecked, dull green upper sides and pale green undersides.  Cotyledon leaf stalks are ridged.  Stems are green with a red base.  The young true leaves are egg shaped, smooth and flat along edges, hairless, possibly red-flecked. 

Mature plants form vigorous basal rosettes.  All leaves have a transparent, thin membrane (ocrea) covering the leaf-stem juncture.  Flower stalks are chestnut to red-brown with smaller and more tapered leaves than those in the rosette. Underground part of both species consists of a large, fleshy, yellow taproot which is surmounted by about 2” (5 cm) of underground stem containing many buds.  The root and underground stem are difficult to distinguish but behave differently when fragmented by tillage (see Response to disturbance) 

• Broadleaf dock:  Leaves are 12” (30 cm) long by 6” (15 cm) wide, hairless, tapered, and heart shaped at the base; they are flatter, less wavy, broader, and less crinkled than curly dock.  Lower leaf stalks may have red veins.   The taproot is usually highly branched.
• Curly dock:  Rosette leaves are curly, wavy, crinkly-edged, elongated, and tapered at the base.  Rosette leaves are 6-12” (15-30 cm) long and up to 2.5” (6 cm) wide.  Stem leaves are up to 6” (15 cm) long and 1” (2.5 cm) wide.  Leaves are alternate, hairless, shiny, green, increasingly ruddy as the season progresses.  The taproot is often unbranched or only minimally branched.

Flowers are green-red, inconspicuous, small, without petals, and arranged into spiral clusters at the ends of closely spaced, stalk branches.  Individual flowers hang from the cluster on small stalks.  The inflorescence turns red-brown as the seeds mature.

• Broadleaf dock:  Stalks are hairless, 3-4 ft (0.9-1.2 m) tall, and occasionally present in small groups.  Flowers are 0.07-0.1” (0.18-0.25 cm) wide.   Clusters make up two thirds of the stem length.
• Curly dock:  Stalks are jointed, reddish-brown, hairless, and up to 5 ft (1.5 m) tall. Flowers are 0.25” (0.6) wide.  Clusters are 6-24” long. 

Fruit and Seeds:  Both species have heart-like, winged brown fruits surrounding three-sided, tear-drop shaped, glossy, reddish brown seeds.

• Broadleaf dock:  Wings on fruits are reddish brown, 0.13-0.25” (0.33-0.63 cm) long, toothed, and spiny.  Seeds are 0.08” (0.20 cm) long when removed from fruit.
• Curly dock:  Wings on fruits are corky or papery, dark brown, 0.13-0.25” (0.33-0.63 cm) long, and entire.  Seeds are 0.07” (0.18 cm) long when removed from fruit.

Similar species:  Common burdock (Arctium minus Bernh.) and great burdock (Arctium lappa L.) have young seedlings similar to the docks.  Seedlings of burdocks have smooth, shiny cotyledons with downy undersides.  Young true leaves have leaf stalks that encase the stem, whereas dock stems extend around the leaf stalk.  Docks have ocreas, whereas burdocks do not.

Management

Both species proliferate in poorly managed pastures.  They establish well in bare, trampled areas where livestock congregate (Pye et al. 2011).  With intensive rotational grazing, small dock plants are eaten and trampled back before they get well established, and the rapid regrowth of the grass will tend to out-compete the dock.  Broadleaf dock had fewer plants and smaller taproots when ryegrass-white clover swards were cut four times per season (simulating grazing) than when cut twice per season (for silage) (Humphreys et al. 1999).  Other experiments have shown similar decreases in vigor of dock as cutting frequency increases (Stilmant et al. 2010, van Evert et al. 2020).  Although most livestock will not eat dock unless it is very young, deer and some breeds of sheep will eat even large plants.  High seeding rates reduce dock infestations in newly established crops of both grasses and alfalfa.  Similarly, undersowing to increase the density of thinning grass stands can help suppress dock (Zaller 2004).  

In both forage crops and annual crops, dock problems increase with over fertilization (Niggli et al. 1993, Zaller 2004).  Moderate fertility rates are the key: you want enough nitrogen for the crop to grow vigorously and compete with the dock for light, but excess N will favor the dock relative to the crop.

Tillage is effective for managing dock (Zaller 2004).  The worst problems in annual crops come when the field is rotated from a perennial forage to an annual crop.  If the dock becomes old and dense in the forage phase of the rotation, special measures are needed to get it under control.  One approach is to plow the field in mid-summer and work the dock roots to the surface where they can dry out using a spring tooth harrow.  Turn the soil and roots periodically with the harrow to ensure a good kill.  Another successful approach is to rototill the field to a depth of about 4” (10 cm).   This will chew up the underground vertical stem from which most new shoots arise.   The rotary tillage should be slow to pulverize the underground stems to the maximum degree.  Simply severing the neck from the root can actually increase regeneration (Pye et al. 2011).    Follow the initial rotary tillage with faster passes using other implements to kill new sprouts.  This approach can be used to spot treat heavily infested areas of a pasture or forage field.  Successive tillage operations should occur when the leaves are 2” (5 cm) long (Foster 1989).  Moldboard plowing will reduce dock populations, but some plants will recover even from burial at the bottom of the plow layer (Pye et al. 2011).  A mechanical dock puller that can remove 600 plant/hr has been developed in Germany (Pötsch 2003).

Since both dock species have very long growing seasons, winter cover crops help to suppress dock populations through competition.  Prevention of new infestations (see Dispersal) and early eradication of isolated plants can prevent much grief, particularly on farms with perennial forage and pasture.

Ecology

Origin and distribution:  Both species are native to Europe.  Both species have been introduced widely in Asia, Africa, Australia and North and South America.  Broadleaf dock occurs as far north as Greenland, and curly dock occurs in Iceland and the interior of Alaska (Cavers and Harper 1964).  In North America, broadleaf dock is most common east of the Mississippi River and in the Pacific Northwest, with populations more scattered in the Great Plain and Inter-Mountain states.  Curly dock, however, occurs throughout the U.S.A. and the agricultural zones of Canada (USDA Plants).

Seed weight:  Broadleaf dock: 0.7-2.8 mg (EFBI), 1.3 mg (Milberg et al. 2000), 1.6-2.2 mg (Cavers and Harper 1966).  Curly dock: 1.0-3.0 mg (Cavers and Harper 1964, 1966), 1.3-1.6 mg (Hejcman et al. 2012), 1.4 mg (Stevens 1932, Milberg et al. 2000).

Dormancy and germination:  For both species, seed dormancy characteristics apparently depend on growth conditions and vary greatly between individuals and position of the seed on the seed stalk (Cavers and Harper 1964, 1966).  Broadleaf dock seeds are dormant when shed, but gradually lose dormancy during succeeding months (Benvenuti et al. 2001).  Germination occurs at 50-95 °F (10-35 °C) with maximum germination at 68-77 °F (20-25 °C) (Benvenuti et al. 2001).  Temperature alternation and light increase germination (Cavers and Harper 1966), whereas exposure to light filtered through leaves decreases germination (Benvenuti et al. 2001, Roberts and Totterdell 1981).  Exposure to high nitrate levels reduces germination at optimal light levels (Milberg 1997).  Seeds from early bolting plants are more dormant than those from late bolting plants (Honěk and Martinková 2002). 

Curly dock seeds are dormant when the dry fruit hull surrounding the seed restricts germination (Hemmat et al. 1985), but may be non-dormant when shed at maturity in summer (Baskin and Baskin 1985).  Exposure of moist seeds to low temperatures of 32-59 °F (0-15 °C) for one or more weeks breaks dormancy (Cavers and Harper 1964, Roberts and Totterdell 1981).  Exposure to temperature alternations and light promote germination (Baskin and Baskin 1985, Cavers and Harper 1966).  Seeds germinate in response to a wide range of alternating day/night temperatures ranging from 68/50 °F (20/10 °C) to 95/68 °F (35/20 °C) (Baskin and Baskin 1985, Roberts and Totterdell 1981).  High N along with a deficiency of P and K fertilization of the mother plant reduces seed germination (Hejcman et al. 2012).  Secondary dormancy can be induced by several days of warm temperatures up to 86 °F (30 °C) or dry conditions (Duke 1978, Roberts and Totterdell 1981, Samimy and Khan 1983).  Although most research has been conducted on each of these species separately, an extensive review suggests both species have similar dormancy and germination behavior (Roberts and Totterdell 1981).

Seed longevity:  Seeds of broadleaf dock can survive at least 40 years under favorable conditions and seeds of curly dock can remain viable in the soil for as long as 80 years (Burnside et al. 1996, Cavers and Harper 1964, Kivilaan and Bandurski 1981, Toole and Brown 1946).  In pastures, seed densities of several thousand per square foot are common (Zaller 2004).  Nevertheless, seed mortality can be high.  In one experiment in Ontario, less than 15% of curly dock seeds and 1% of broadleaf dock seeds survived more than one year (Weaver & Cavers 1979).  In a series of five-year experiments in which the top 3” (7.5 cm) of soil was stirred three times per year, seeds of curly dock declined by an average of 37-47% per year and seeds of broadleaf dock declined by 49-56% per year (Roberts and Neilson 1980).

Season of emergence:  Seedlings emerge throughout the growing season, but notable flushes of emergence occur during the spring and fall (Cavers and Harper 1964) when soil temperature is above 59 °F (15 °C) and daily fluctuations are greatest (Roberts and Totterdell 1981).  Overwintering rosettes resume growth in early spring (Cavers and Harper 1964, Doll 2002).

Emergence depth:  Emergence of dock seedlings is best at or near the soil surface, but a few seedlings can emerge from as deep as 2-3” (5-8 cm) (Benvenuti et al. 2001, Boyd & Van Acker 2003, Weaver and Cavers 1979).  Emergence from fragments of below ground stems can occur from 8” (20 cm) depth if soil is not waterlogged, but emergence is best from 0 to 3” (7.5 cm) (Pino et al. 1995, Pye et al. 2011, Zaller 2004).

Photosynthetic pathway:  C3

Sensitivity to frost:  Established plants of both species are very frost tolerant, and commonly overwinter as a rosette of small reddish leaves (Cavers and Harper 1964), though curly dock sometimes dies completely back to the ground.  Seedlings of broadleaf dock are frost sensitive.

Drought tolerance:  Mature plants of broadleaf dock are drought tolerant (Gilgen and Feller 2013, Pino et al. 1995), but seedlings can die from prolonged drought conditions (Cavers and Harper 1964).  Curly dock is very drought tolerant (Cavers and Harper 1964). 

Mycorrhiza:  Most reports describe the absence of mycorrhiza from both species (Harley and Harley 1987, Pendleton and Smith 1983, Vatovec et al. 2005).  However, one study reported the presence of mycorrhiza (Harley and Harley 1987).

Response to fertility:  Both species respond strongly to N (Niggli et al. 1993), and their high abundance is an indicator of excessive N fertility (Zaller 2004).  Curly dock responds most to N and P together, and seed production is enhanced most by balanced N, P, and K (Hejcman et al. 2012).  Curly dock responds more to P than to K (Hoveland et al. 1976).  Curly dock foliage contains high concentrations of Zn, but whether it also requires high Zn levels in the soil is unclear.

Soil physical requirements:  These species are present on almost all soil types, but less so on peat or very acidic soils (Cavers and Harper 1964. Zaller 2004).  Curly dock is an indicator of compaction.  It tolerates waterlogged soils and several weeks of complete immersion in flood water (Lenssen & De Kroon 2004).

Response to shade:  Neither species establishes well in closed communities, such as a well-managed, vigorous pasture (Cavers and Harper 1964, Hongo 1989a,b).  However, regrowth after a period of intense competition and shading was surprisingly high (Niggli et al. 1993).

Sensitivity to disturbance:  Mowing has little effect on above-ground growth of both species but reduces below-ground growth (Hujerová et al. 2013, Zaller 2004).  Leaves are quickly regenerated and mowing induces production of new flowering stalks (Cavers and Harper 1964).  Broadleaf dock was better adapted to frequently cut grasslands than curly dock because of greater investment in root biomass (Hongo 1989a).  However, weekly cutting of broadleaf dock for over three months eventually reduced leaf regrowth to almost nil while depleting root reserves; this reduced plant competitive capacity in the cutting year, but had no effect on plant regeneration in the subsequent spring (van Evert et al. 2020).

Docks tolerate extreme trampling, and often become dominant in areas where cattle congregate (Cavers and Harper 1964).  New plants establish readily from fragments of the short, vertical underground stem that sit on top of the roots (Pino et al. 1995, Pye et al. 2011).  New plants will also form from fragments of the true root, but apparently only in the spring (Cavers and Harper 1964).

Time from emergence to reproduction:  Broadleaf dock rarely flowers during the first season (Cavers and Harper 1964, Zaller 2004).  Curly dock can flower during either the first or second seasons, depending on conditions (Cavers and Harper 1964, Hejcman et al. 2012).  In subsequent years, both species make new flower stalks repeatedly from spring until hard frost in late autumn.  Curly dock that begins regrowth in early February to March will begin flowering in April to early May (Cavers and Harper 1964).  Seeds mature 6-18 days after flowers open (Zaller 2004).  The majority of plants become capable of regeneration from rootstock at 38 to 51 days after planting (Monaco and Cumbo 1972).

Pollination:  Both species are wind and bee pollinated but both have a high degree of self-fertility (Cavers and Harper 1964).

Reproduction:  Seed production is proportional to the size of the plant and varies from 100 to over 60,000 seeds per plant (Cavers and Harper 1964, Hejcman et al. (2012).  About half of curly dock plants die after flowering and a typical plant lives about 3 years (Cavers and Harper 1964).  Both species are relatively short-lived perennials with less than 2% of broadleaf dock and 4-24% of curly dock surviving for more than 4 years (Hongo 1989b).  Vegetative reproduction is limited to expansion of the diameter of old clumps unless the plant is broken by tillage.  Flowering plants allocate substantially less biomass to roots than non-flowering plants (Hujerová et al. 2013).  Even after tillage, most new individuals arise from seeds rather than fragments of roots or underground stalks.

Dispersal:  The seeds blow short distances in the wind.  They also disperse by floating on water (Kelley and Bruns 1975, Wilson 1980).  The wings of the fruit tend to cling to clothing and the fur of animals.  Long distance dispersal probably occurs, however, by passage through livestock, with the seeds being deposited in new locations when the animals are moved or the manure is spread (Mt. Pleasant and Schlather 1994).  The seeds in manure often come from infested pastures.  Seeds may also be present in small grain, forage and cover crop seed.  Birds also disperse the seeds.  (Cavers and Harper 1964, Zaller 2004)

Common natural enemies:  Deer apparently prefer dock over other forage (Cavers and Harper 1964).  Host specific natural enemies normally cause little damage to these species (Zaller 2004).  In an experiment, simultaneous application of the rust Uromyces rumicis and the beetle Gastrophysa viridula greatly reduced leaf area and subsequent regrowth of broadleaf dock (Keary and Hatcher 2004).  Curly dock was more susceptible than broadleaf dock to U. rumicis infection (Schubiger et al. 1986).

Palatability:  Leaves of broadleaf dock were formerly cooked and eaten like spinach, or fed to pigs.  Cattle, sheep, horses, rabbits and chickens all reject the foliage and may be poisoned if forced to eat it due to lack of other forage (Cavers and Harper 1964).  Curly dock has low digestibility and palatability and was completely rejected by grazing lambs (Bosworth et al. 1985, Marten et al. 1987).

Notes:  Extracts and residue of broadleaf dock inhibit growth of a wide range of crops, including white clover, sunflower, wheat, barley, corn and soybean (Zaller 2004). 

References:

• Baskin, J. M., and C. C. Baskin.  1985.  Does seed dormancy play a role in the germination ecology of Rumex crispus?  Weed Science 33:340-343.
• Benvenuti, S., M. Macchia, and S. Miele.  2001.  Light, temperature and burial depth effects on Rumex obtusifolius seed germination and emergence.  Weed Research 41:177-186.
• Bosworth, S. C., C. S. Hoveland, and G. A. Buchanan.  1985.  Forage quality of selected cool-season weed species.  Weed Science 34:150-154.
• Boyd, N. S. and R. C. Van Acker.  2003.  The effects of depth and fluctuating soil moisture on the emergence of eight annual and six perennial plant species.  Weed Science 51:725-730.
• Burnside, O. C., R. G. Wilson, S. Weisberg, and K. G. Hubbard.  1996.  Seed longevity of 41 weed species buried 17 years in eastern and western Nebraska.  Weed Science 44:74-86.
• Cavers, P. B. and J. L. Harper.  1964.  Rumex obtusifolius L. and R. crispus L.  Journal of Ecology 51:737-766.
• Cavers, P. B., and J. L. Harper.  1966.  Polymorphism in Rumex crispus and Rumex obtusifolius. Journal of Ecology 54:367-382.
• Doll, J.  2002.  Knowing when to look for what: Weed emergence and flowering sequences in Wisconsin.  http://128.104.239.6/uw_weeds/extension/articles/weedemerge.htm.
• Duke, S. O.  1978.  Interactions of seed water content with phytochrome-initiated germination of Rumex crispus (L.) seeds.  Plant and Cell Physiology 19:1043-1049.
• EFBI.  Ecological Flora of the British Isles, accessed 11/28/2016.  http://www.ecoflora.co.uk/
• Foster, L.  1989.  The biology and non-chemical control of dock species Rumex obtusifolius and R. crispus.  Biological Agriculture and Horticulture 6:11-25.
• Gilgen, A.K., and U. Feller.  2013.  Drought stress alters solute allocation in broadleaf dock (Rumex obtusifolius).  Weed Science 61:104-108.
• Harley, J. L., and E. L. Harley.  1987.  A check-list of mycorrhiza in the British flora.  New Phytologist 105:1-102.
• Hejcman, M., V. Křištálová, K. Červená, J. Hrdličková, and V. Pavlů.  2012.  Effect of nitrogen, phosphorus, and potassium availability on mother plant size, seed production and germination ability of Rumex crispus.  Weed Research 52:260-268.
• Hemmat, M., G.-W. Zeng, A. A. Khan.  1985.  Responses of intact and scarified curly dock (Rumex crispus) seeds to physical and chemical stimuli.  Weed Science 33:658-664.
• Honěk, A., and Z. Martinková.  2002.  Effects of individual plant phenology on dormancy of Rumex obtusifolius seeds.  Weed Research 42:148-155.
• Hongo, A.  1989a.  Survival and growth of seedlings of Rumex obtusifolius L. and Rumex crispus L. in newly sown grasslands.  Weed Research 29:7-12.
• Hongo, A.  1989b.  Transplant survival of Rumex obtusifolius L. and Rumex crispus L. in three old reseeded grasslands.  Weed Research 29:13-19.
• Hoveland, C. S., G. A. Buchanan, and M. C. Harris.  1976.  Response of weeds to soil phosphorus and potassium.  Weed Science 24:194-201.
• Hujerová, R., V. Pavlů, M. Hejcman, L. Pavlů, and J. Gaisler.  2013.  Effect of cutting frequency on above- and belowground biomass production of Rumex alpinus, R. crispus, R. obtusifolius, and the Rumex hybrid (R. patienta x R. tianschanicus) in the seeding year.  Weed Research 53:378-386.
• Humphreys, J., T. Jansen, N. Culleton, E. S. Macnae, and T. Storey.  1999.  Soil potassium supply and Rumex obtussifolius and Rumex crispus abundance in silage and grazed grassland swards.  Weed Research 39:1-13.
• Keary, I. P., and P. E. Hatcher.  2004.  Combining competition from Lolium perenne and an insect-fungus combination to control Rumex obtusifolius seedlings.  Weed Research 44:33-41.
• Kelley, A. D., and V. F. Bruns.  1975.  Dissemination of weed seeds by irrigation water.  Weed Science 23:486-493.
• Kivilaan, A., and R. S. Bandurski.  1981.  The one hundred-year period for Dr. Beal's seed viability experiment.  American Journal of Botany 68:1290-1292.
• Lenssen, P. M. and H. De Kroon.  2004.  Abiotic constraints at the upper boundaries of two Rumex species on a freshwater flooding gradient.   Journal of Ecology 93:138-147.
• Marten, G. C., C. C. Sheaffer, and D. L. Wyse.  1987.  Forage nutritive value and palatability of perennial weeds.  Agronomy Journal 79:980-986.
• Milberg, P.  1997.  Weed seed germination after short-term light exposure: germination rate, photon fluence response and interaction with nitrate.  Weed Research 37:157-164.
• Milberg, P., L. Andersson, and K. Thompson.  2000.  Large-seeded species are less dependent on light for germination than small-seeded ones.  Seed Science Research 10:99-104.
• Monaco, T. J., and E. L. Cumbo.  1972.  Growth and development of curly dock and broadleaf dock.  Weed Science 20:64-67.
• Mt. Pleasant, J., and K. J. Schlather.  1994.  Incidence of weed seed in cow (Bos sp.) manure and its importance as a weed source for cropland.  Weed Technology 8:304-310.
• Niggli, U., J. Nösberger, and J. Lehmann.  1993.  Effects of nitrogen fertilization and cutting frequency on the competitive ability and the regrowth capacity of Rumex obtusifolius L. in several grass swards.  Weed Research 33:131-137.
• Pendleton, R. L., and B. N. Smith.  1983.  Vesicular-arbuscular mycorrhizae of weedy and colonizer plant species at disturbed sites in Utah.  Oecologia 59:296-301.
• Pino, J., R. J. Haggar, F. X. Sans, R. M. Masalles, and R. N. Sackville Hamilton.  1995.  Clonal growth and fragment regeneration of Rumex obtusifolius L.  Weed Research 35:141-148.
• Pötsch, E. M.  2003.  Möglichkeiten dermechanisch/biologischen Ampferbekämpfung.  Landbauforschung Völkenrode 255:63-68.
• Pye, A., L. Anderson, and H. Fogelfors.  2011.  Intense fragmentation and deep burial reduce emergence of Rumex crispus L.  Acta Agriculturae Scandinavica, Section B—Soil and Plant Science 61:5, 431-437.
• Roberts, E. H., and S. Totterdell.  1981.  Seed dormancy in Rumex species in response to environmental factors.  Plant Cell and Environment 4:97-106.
• Roberts, H. A. and J. E. Neilson.  1980.  Seed survival and periodicity of seedling emergence in some species of Atriplex, Chenopodium, Plygonum and Rumex.  Annals of Applied Biology 94:111-120.
• Samimy, C., and A. A. Khan.  1983.  Secondary dormancy, growth-regulator effects, and embryo growth potential in curly dock (Rumex crispus) seeds.  Weed Science 31:153-158.
• Schubiger, F. X., G. Défago, H. Kern, and L. Sedlar.  1986.  Damage to Rumex crispus L. and Rumex obtusifolius L. caused by the rust fungus Uromyces rumicis (Schum.) Wint.  Weed Research 26:347-350.
• Stevens, O. A.  1932.  The number and weight of seeds produced by weeds.  American Journal of Botany 19:784-794.
• Stilmant, D., B. Bodson, C. Vrancken and C. Losseau.  2010.  Impact of cutting frequency on the vigour of Rumex obtusifolius.  Grass and Forage Science 65:147-153.
• Toole, E., and E. Brown.  1946.  Final results of the Duvel buried seed experiment.  Journal of Agricultural Research 72:201-210.
• USDA Plants.  USDA, Natural Resources Conservation Service.  http://plants.usda.gov
• van Evert, F. K., M. Cockburn, J. E. Beniers, and R. Latsch.  2020.  Weekly defoliation controls but does not kill broad-leaved dock (Rumex obtusifolius L.).  Weed Research 60:161–170.
• Vatovec, C., N. Jordan, and S. Huerd.  2005.  Responsiveness of certain agronomic species to arbuscular mycorrhizal fungi.  Renewable Agriculture and Food Systems 20:181-189.
• Weaver, S. J., and P. B. Cavers.  1979.  Dynamics of seed populations of Rumex crispus and R. obtusifolius (Polygonaceae) in disturbed and undisturbed soil.   Journal of Applied Ecology 16: 909-917.
• Wilson, Jr., R. G.  1980.  Dissemination of weed seeds by surface irrigation water in western Nebraska.  Weed Science 28:87-92.
• Zaller, J. G.  2004.  Ecology and non-chemical control of Rumex crispus and R. obtusifolius (Polygonaceae): a review.  Weed Research 44:414-432