Broad Leaved Dock Descriptive Essay
Botanical name: Rumex obtusifolius
Family name: Polygonaceae
There are a number of different dock species that grow within New Zealand, but broad-leaved dock would be the most common of these. So when people say they have problems with docks, they are usually referring to broad-leaved dock. It is a perennial weed which has a large tap-root system. It can vary in size quite considerably, sometimes surviving in regularly mown lawns by producing small, prostrate leaves, but usually growing quite large in pastures and waste areas, out-competing surrounding plants by covering them with its broad leaves. It generally has a growing point at ground level from which is produces its large leaves, but every spring it forms an upright stem on which it forms fruits which start out green, turn red and eventually become dark brown as they dry out. The seeds produced by docks each year are long-lived, so huge banks of dock seeds can build up within the soil. When dock-infested paddocks get cultivated, the soil is soon reinfested by docks, both from seedlings and also because the tap-roots are seldom killed by cultivation and so regrow, as shown in recent research we conducted. The foliage of docks contains tannins which makes them somewhat unpalatable to some livestock, especially cattle and horses. Sheep will generally eat docks, but cows aren’t keen on them, so docks can become quite a problem on dairy farms. Docks are more tolerant of poorly drained soil than many other plant species, so are often found growing prolifically in low-lying parts of paddocks.
The leaf shape of some of the more common Rumex weeds are shown on the right. The docks are closely related to sheep's sorrel, which is also grouped in the Rumex genus. Another common dock found in pastures and waste areas is clustered dock, which tends to have a narrower leaf than broad-leafed dock. The broad-leaved dock leaf is usually wider near the base than near the tip, whereas clustered dock has less of a change in width from one end of the leaf to the other. Fiddle dock gets its name from being shaped like a fiddle or violin, so is easier to differentiate from broad-leaved dock. As with many weeds, the leaves that grow from the base of the plant are better for telling the docks apart than those up the flower stems, which aren’t always the typical shape. The fruits of docks, once they have matured, are about 2-3 mm across and are often also used to tell dock species apart. In the photo below, you can see that broad-leaved dock fruits tend to each have three "wings" with jagged edges, unlike clustered dock fruits. There are three equal-sized inflated "bladders" on the fruits of clustered dock, whereas broad-leaved dock has one large bladder and two smaller ones for each fruit.
Docks as a group are quite difficult to kill. They have a moderate tolerance of most herbicides, and glyphosate needs to be applied at a fairly high rate when controlling docks in waste areas or when spraying out pastures during seed-bed preparation. A common recommendation now when spraying out pastures is to add thifensulfuron (eg Harmony) to the glyphosate to give better control of the docks without needing to apply such high rates of glyphosate. Glyphosate is recommended not to be applied while the plant has a seed-head. For selective control of docks in pastures, the hormone herbicides such as 2,4-D and MCPA are ineffective at controlling established plants. For many years, the standard recommendation in pastures has been to apply asulam (Asulox or Dockstar). Recently, another treatment has become available, namely thifensulfuron (eg Harmony), which tends to be cheaper than asulam. Both herbicides should be applied in spring while docks are actively growing but before seed-head formation has begun. Both of them will cause temporary suppression of pasture growth after application due to a severe check of clover growth, and both may require a follow-up application for well-established dock plants. Another possibility is to spot-spray in pastures with aminopyralid (T-Max). If pastures have bad dock problems, it might be best to spray them out with a glyphosate/thifensulfuron mix, resow the pasture then treat new seedlings of docks with a MCPB/bentazone mix (eg Pulsar, PastureGuard Elite, Quasar) or 2,4-DB. In turf, a triclopyr/picloram mix (eg Victory Gold) will give good control. In orchards, either use asulam to spot-spray docks, or add fluroxypyr (eg Solstar) or saflufenacil (Sharpen) to glyphosate to improve the control by the glyphosate.
Description: This herbaceous perennial plant is 2-3½' tall. Initially, it consists of a rosette of basal leaves, from which one or more flowering stalks develop. The basal leaves are up to 1' long and 4" across. Their petioles are long and slender, while their blades are oblong-ovate or oblong-cordate, crisped and slightly undulate along the margins, and glabrous. The central vein of each basal leaf is often tinted red, and a reticulated network of fine secondary veins is observable across the upper surface. The leaf base is slightly cordate or well-rounded, rather than tapering or wedge-shaped. The cauline leaves alternate along the flowering stalks. They are similar in appearance to the basal leaves, although somewhat shorter in length and more narrow; their petioles are also shorter. The stalks are round, slightly ribbed, and glabrous; they often have prominent longitudinal veins that are tinted red. Each stalk terminates in a panicle of whorled racemes up to 1' in length. The whorls of greenish red flowers are somewhat interrupted along the length of the racemes. The flowers droop downward from pedicels about ½" in length when they are fully developed. Each flower is about ¼" long, consisting of 6 sepals (3 inner and 3 outer sepals) and no petals. Like other Rumex spp. (Docks), Bitter Dock is monoecious and has staminate (male) and pistillate (female) flowers on the same plant. Both types of flowers are intermingled together on the racemes. The male flowers have 6 stamens and inner sepals that are dull yellow, while the female flowers have a pistil and inner sepals that are often red. As the female flowers develop, their inner sepals become enlarged and surround a single tubercle (hard-coated seed). Each face of this tripartite fruit is oval-cordate or oval-deltoid in shape; its margins are membranous and there are 2-4 spiny teeth along each margin, particularly in the upper half. In bright sunlight, these fruits often turn bright red and are rather colorful. The blooming period usually occurs during the late spring and lasts about 2 weeks, after which the fruits mature slowly during the first half of the summer. The flowers are wind-pollinated and there is no floral scent. The hard-coated seeds are ovoid-oblongoid and rather large in size. Surrounded by the membranous inner sepals, they can float on water or blow about in the wind. The root system consists of a stout taproot. This plant spreads by reseeding itself.
Cultivation: The preference is full or partial sun, moist to mesic conditions, and a loamy fertile soil. This robust plant will grow readily in less favorable situations, but it will be smaller in size. It can tolerate temporary flooding and is more often in partially shaded situations than many other Rumex spp. (Docks). The seeds of Docks can persist in the ground for several decades and remain viable.
Range & Habitat: The non-native Bitter Dock is a fairly common plant that occurs in the majority of counties in Illinois; it is least common in the NW and north central areas of the state (see Distribution Map). Habitats include moist woodland edges, seeps, semi-shaded areas along streams, gardens and edges of yards, areas along buildings, vacant lots, roadside ditches, and waste areas. Bitter Dock is native to Eurasia and prefers disturbed areas.
Faunal Associations: Because the flowers are wind-pollinated, they attract few pollinating insects. Sometimes beetles and other insects lurk in the dense whorls of flowers and fruits. The foliage of Docks is eaten by the caterpillars of Copper butterflies, including Lycaena hyllus (Bronze Copper) and Lycaena helloides (Purplish Copper). The caterpillars of some moths also eat the foliage of Docks, including Phragmatobia fuliginosa (Ruby Tiger Moth), Sunira bicolorago (Bicolored Sallow), and Phlogophora iris (Olive Angle Shades). The caterpillars of the moth Luperina passer (Rustic Dock) feed on the roots. Various birds eat the seeds of Docks, including the Greater Prairie Chicken, Bobwhite, Redwing Blackbird, Bobolink, Swamp Sparrow, and Song Sparrow. The seeds of Docks are also eaten by some sparrows during the winter, including the Vesper Sparrow, Fox Sparrow, and White-Crowned Sparrow. Ducks occasionally eat the seeds of plants occurring in wetland areas. Mammalian herbivores usually shun the foliage of mature plants because it is bitter and slightly toxic (containing oxalates and nitrates). When livestock are fed the flowering stalks of dock, the seeds can pass through their digestive tracts and remain viable. Thus, these animals can help to spread the seeds into new areas.
Photographic Location: The plants in the photographs occurred in a vacant lot and along a roadside in Urbana, Illinois.
Comments: Bitter Dock is one of the more ornamental species of Docks. It is fairly easy to distinguish from other Docks by its shiny leaves, which are rather broad, well-rounded or cordate at the base, and crisped along their margins. Another distinctive characteristic is the appearance of the calyx, which has spiny teeth along its margins. Another common name for this species is Broad-Leaved Dock.