Weed of the Month: Curly Dock

(Rumex crispus)

Published: April 13, 2015

Curly dock (Rumex crispus), also known as sour dock, yellow dock, narrowleaf dock, or curled dock, is a perennial weed native to Europe, Asia, and parts of Africa. Curly dock was introduced into the U.S., possibly arriving as a seed contaminant in the early 1600’s when the British brought crops and cattle to New England¹. The weed has spread to every U.S. state and Canadian province, and is now considered one of the most widely distributed weeds in the world².

Curly dock prefers moistened soils but can grow in most environments and can be found in pastures, hay fields, forages, landscapes, and some no-till agronomic crops across the U.S. (Figure 1). However, it is rarely a problem in tilled soils.

Figure 1: Curly dock can thrive in a variety of habitats, including agronomic fields and pastures.

Curly dock seed, which can remain dormant in the soil for 80 years³, germinates at various times throughout the year and are stimulated in response to light and temperature fluctuations. The seedling’s cotyledons are round at the apex, narrow at the base, and glabrous (lack hairs) (Figure 2). The hypocotyl region (or the stem between the cotyledons and the soil) may have a maroon tint. Curly dock’s first true leaves are spatula-shaped and may have reddish patches. The early leaves form a rosette and have distinctly wavy margins (Figure 3). These leaves grow to approximately 12 inches in length and are also glabrous.

Figure  2: Curly dock cotyledons are round at the apex and narrow at the base. The young leaves are spatula shaped and may have red patches.

Figure 3: The initial leaves on Curly dock emerge to form a rosette.

As the plant matures, the thick and unbranched stem bolts, reaching up to 5 feet in height and usually having a reddish tint (Figure 4). Leaves along the stem are arranged alternately, are glabrous, and have a membranous sheath that encircles the stem (an ochrea). The stem leaves become progressively smaller up the flowering stalk.

Curly dock is capable of flowering twice a year; the flowers are approximately 1/8th of an inch in length and form clusters on the upper portion of the stem (Figure 4). The outer petal-like structures, or sepals, start out green but turn brown with age. Each plant can produce 100’s to 1000’s of seed, and the seed can easily be moved by wind or water due to the wings on the fruit. Curly dock can also reproduce vegetatively through sprouts that regenerate from buds that form on the taproot.

Figure 4: Curly dock flowers start out green but will brown as the plant matures.

Grazing and mowing can help reduce populations of curly dock. However, the weed has been shown to be toxic when consumed in large amounts. Curly dock seedlings can be controlled effectively with spring herbicide applications. However once the weed becomes established, fall applications may prove more effective.

For selective control of curly dock in grass pastures and hayfields, metsulfuron products (Cimarron, Cimarron Max, Chaparral, etc.), 2,4-D and dicamba combinations (Weedmaster, etc.), or combinations of GrazonNext or Grazon P+D with triplopyr (Remedy, PastureGard, etc.) are effective foliar sprays (Table I).

In established legumes such as alfalfa, curly dock is one of the most common and problematic weed species. Few chemical treatment options exist for control of curly dock in non-Roundup Ready alfalfa stands. Researchers at Penn State have found that Gramoxone Inteon can be applied at 2 to 3 pt/A to established, dormant alfalfa stands in the spring PRIOR TO 2 INCHES OF REGROWTH. Raptor can be applied at a rate of 4 to 6 fl oz/A on seedlings or established alfalfa stands if application is made prior to significant alfalfa growth or regrowth to 3 inches. Pursuit is labeled at a rate of 1.08 to 2.16 oz/A for use in established alfalfa and alfalfa-grass mixtures and can be effective when applied on curly dock seedlings. Glyphosate is an effective foliar spot-spray option; however, it is non-selective and will injure any portion of the crop that it contacts.

Curly dock can also become a problem weed of no-till corn or soybean systems and must be dealt with prior to planting in the spring. While it is difficult to achieve complete control of the rootstocks with any treatment, there are a number of herbicide combinations that will provide adequate desiccation of the above-ground foliage such that this weed will not be a problem in the subsequent corn or soybean crop. Higher rates of glyphosate in combination with 2,4-D or dicamba will provide good control of curly dock, but keep in mind the plant back restrictions that are required after application of 2,4-D and dicamba. Paraquat (Gramoxone) plus 2,4-D or dicamba can also provide acceptable control of curly dock prior to planting, but as mentioned previously plants will likely re-emerge from the stout taproots in the following year.

Table 1: Curly dock response to herbicides for grass pastures****

*See herbicide labels for grazing and foraging restrictions
**A variety of trade names exist.
***Key:
E = Excellent, >90% control
G = Good, 80 to 90% control
F = Fair, 60 to 80% control
P = Poor, <60% control
****Data taken from the 2015 University of Missouri Extension Publication IPM1031 “Weed and Brush Control For Forages, Pastures, and Non-cropland”

To see more images of curly dock, visit weedid.missouri.edu.

To learn more about weed and brush control in pasture and non-crop settings, purchase a copy of extension publication IPM1031 at: http://extension.missouri.edu/p/ipm1031

¹Mack RN and M Erneberg (2002) The United States Naturalized Flora: Largely the Product of Deliberate Introductions. Annals of the Missouri Botanical Garden 89(2): 176-189.

²Hujerova R, Pavlu V, Hejcman M, Pavlu L, and J Gaisler (2013) Effect of cutting frequency on above- and below-grownd biomass production of Rumex alpinus, R. cripsus, R. obtusifolius, and the Rumex hybrid (R. patient x R. tianschanicus) in the seeding year. Weed Research 53:378-386.

³Kivilaan A and RS Bandurski (1973) The Ninety-Year Period for Dr. Beal’s Seed Viability Experiment. American Journal of Botany 60(2): 140-145.