Curly dock weed seed

Weed of the Month: Curly Dock

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 England 1 . 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 world 2 .

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 years 3 , 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).

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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.

Curly dock

General description: Basal rosette of elongated leaves (up to 12 in long) with wavy margins. Leaves are a dull green. Flowering stem has a few leaves and reaches heights of 3 ft. Flowers have green sepals; mature into brown, 3-sided winged structure surrounding the achene.

Key ID traits: Rosette of wavy, elongated leaves. Leaves of rosette have large, ‘slimy’ ochrea usually positioned below the soil line. Flower stalk with clusters of winged achenes. Achenes turn dark brown when mature.

Similar species: There are several closely related Rumex species similar in appearance to curly dock. The wavy leaf margin is the key vegetative trait to identify curly dock. Pale dock (Rumex altissimus) has similar shaped leaves, but leaves are glossy and don’t have the wavy margin. Broadleaf dock (Rumex obtusifolius) leaves are approximately half was wide as they are long, whereas curly and pale dock leaves are much narrower.

Miscellaneous: A native of Europe, curly dock was first observed in North America in the 1700s.

Curly dock produces a rosette of elongated leaves with wavy leaf margins in the spring.

As the stem elongates large ochreas are visible surrounding the leaf petioles.

Curly dock produces dense panicles, seed have small wings and turn dark brown when mature.

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Pale/sour dock has a similar growth habit as curly dock, but the leaf margins are smooth rather than wavy.

Curly Dock: A Plant for Year-Round Sustenance

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Curly dock plants displaying their voluminous seedheads.

Curly dock (Rumex crispus, also called yellow dock) is one of those plants that is easily overlooked. It doesn’t have a showy flower and the leaves can look kind of generic. Furthermore, it’s not typically as prolific of a weed as dandelion— at least not in urban areas. It’s unfortunate that people aren’t more familiar with it, as the leaves, stem, seed, and root are all edible or medicinal. And with its wide distribution, it’s easy to start eating!

Habitat and Distribution

Curly dock isn’t too discerning about its habitat, growing in full sun and part shade, fields, roadsides, trailsides, and other open areas. Native to Europe, it has been introduced to all fifty states in the US and all Canadian provinces except Nunavut.

Identification

The leaves of curly dock are hairless, long and narrow, and often have wavy or curly edges—which is where it gets its common name. The plant has both basal leaves and leaves on the stem, which are alternate. Basal leaves can be as long as 12 inches and around 2 ½ inches wide; the leaves become smaller as they ascend the stem. A thin whitish sheath grows around the node (where the petiole and stalk meet.) This sheath become brown and papery with time, and eventually disintegrates. The main stem is ribbed, stout, and mostly unbranched. The plant can reach heights of one to five feet at maturity.

Flowers grow in branching clusters at the top of the plant, in groups of 10 to 25. Despite this large quantity, they are rather inconspicuous because they are small and greenish (though they can also be yellowish or pinkish.) They appear in whorls, meaning that they grow all the way around a single point on the stem.

Seeds appear in late summer and fall. They are three-sided, oval to egg-shaped, with a sharp point on one end. The seeds are encased in a leaf-like capsule that turns brown and papery with age. These seeds are the best way to identify curly dock in winter, as they often remain on the dead stalk until spring. (See below for close-up pictures of the seeds.) If you are unfamiliar with curly dock, I don’t recommend immediately picking a dead winter stalk for the seeds. Instead, practice positively identifying the plant during the growing season. Then observe the plant as it ages through the fall and winter, and then start picking the dead winter stalks. I believe that this is best way to learn to identify plants in winter.

Similar Species

Broad-leaved dock (Rumex obtusifolius)

Many species of dock (Rumex spp.) grow in the United States and Canada. Besides curly dock, broad-leaved dock (Rumex obtusifolius) is the main species that’s eaten. This dock has large, broad heart-shaped leaves, unlike the long, narrow leaves of curly dock. The leaves, stem, and seeds of broad-leaved dock can be eaten like those of curly dock, but the root does not have the same medicinal qualities. Broad-leaved dock can be found in all 50 US states except Nevada, Wyoming, and North Dakota. In Canada, it grows in Quebec, Ontario, and British Columbia.

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Western dock (R. occidentalis), dooryard dock (R. longifolius), field dock (R. stenphyllus), wild rhubarb (R. hymenosepalus) and patience dock (R. patientia) are all edible as well. As far as I know, there are no poisonous species of dock, though some are considered inedible due to unpalatability.

Harvest and Preparation

The creases along this dock leaf is a sign that it unfurled recently and is therefore likely tender and delicious.

Leaves and Stem

Start looking for dock leaves in early spring. Typically the sooner you get them, the more sweet and tender they are, but this depends on growing conditions. I used to hate dock, and could not for the life of me understand how people could compare it to spinach. Then I found a beautiful stand of it growing in an open pine forest. The leaves were large, light green, and supple; and they tasted just like spinach! No, better, even—the sour, lemony aspect was much more pronounced. I didn’t like all the previous dock leaves I had eaten because they were stressed out and stunted from growing in poor, gravelly soils. This is why with foraging it’s important to try species from varying locations!

Regardless, dock leaves can be eaten raw or cooked. When the plant sends up a stem, the basal leaves generally become too tough and bitter to eat, but those on the stem may be palatable. However, the best portion is the stem itself! Harvest dock stems in late spring and early summer, before it reaches full height and any flowers appear. It should feel supple and bendy; if not, it’s probably too tough to eat. The outer layer may be stringy, but this can be peeled before eating. If it’s tender enough, eat it raw; otherwise it’s delicious steamed or sautéed. You could even pickle it! The flavor is similar to the leaves, except more “green” tasting—something like green beans.

Dock leaves and stems contain oxalic acid, which is what gives them their yummy sour flavor. However, this does require a note of caution, as oxalic acid prevents the assimilation of minerals such as calcium and iron. But this compound is also found in many cultivated plants, including rhubarb, spinach, and Swiss chard. While one often reads warnings about oxalic acid in wild food literature, one rarely hears warnings about eating those domesticated foods. I believe that this is due to an unfair bias against wild foods. As long as you’re not severely mineral deficient, and as long as you’re not consuming unreasonably massive amounts of foods containing oxalic acid, you’ll be fine!