Family: Smartweed Family (Polygonaceae)
Origin and Distribution: Broadleaf dock is a native of Europe that is found on all continents as a weed of pastures, small grains, and reduced tillage cropland. It is also a weed in orchards, lawns, and home gardens as well as along roadsides and waste areas. Broadleaf dock is found throughout Ohio, especially in the unglaciated southeastern counties. It is usually found on floodplains, along borders of woods, around buildings, in poorly drained and nutrient rich soils, but is also common in some upland sites and on acid soils.
Plant Description: Broadleaf dock is a rosette-forming perennial with a deep taproot that can reach depths of up to 5 feet. It reproduces primarily by seeds, but there is limited regeneration from root tissues. The plants grow as a basal rosette with relatively large leaves. The hairless reproductive stem may reach heights up to 5 feet and will have smaller versions of the basal leaves arranged alternate. The smartweed family is characterized by a papery sheath (called the ocrea) that cover each node. Terminal clusters of small inconspicuous flowers with greenish petals (which turn red at maturity) are formed on the reproductive stems from June through September. Flowers do not contain any nectar and are wind-pollinated. Seedlings are capable of flowering in the first season. A cork-like 3-winged triangular fruit surrounds each seed; this fruit is buoyant and can be dispersed by water. One plant of curly dock can produce up to 60,000 seeds per year. In a long-term weed seed burial study, approximately 83% of the seeds of curly dock were still viable after 20 years. In a similar study started in 1879, about 2% of curly dock seeds were found to be viable after 80 years. Seeds are destroyed in passing through chickens and are relatively short-lived in silage. However, they can pass through other birds and cattle without loss of viability.
- Root system - The root system is a stout, somewhat branched, yellow taproot that may extend as deep as 4 feet.
- Stems - Stems are erect, tall (1 to 4 feet), and sparsely branched, arising solitary or in small groups from the root crown. A tall membranous sheath (ochrea) surrounds the stem above each node. Stems are smooth, sometimes ridged, and become red-brown with age. The erect rust-colored stems often persist into winter.
- Leaves - Cotyledons are three times as long as wide; first true leaves are round. Subsequent leaves are broad, twice as long as wide, with heart-shaped basal lobes and somewhat wavy (but not curly) margins. Newly emerging leaves are distinctly laterally rolled. The petioles and veins on the under side are covered with short, white hairs. Rosette leaves are oblong, often with red veins and/or red spots on the upper surface. Upper leaves are smaller, lance-shaped, with pointed tips, and are arranged alternately on the stem (one per node).
- Flowers - Flowers are not showy, but are made up of small, green sepals (no petals) that turn brown at maturity. They appear in loose whorls along the upper part of the elongating and branched stem. The flowers lack nectar and pollen is spread by wind.
- Fruits & Seeds - The fruits of broadleaf dock are generally triangular, with jagged spreading teeth along the margins of the membranous 'wings' (sepals). Fruits contain a single glossy red-brown triangular seed enclosed in only one of the 3 sepals. A single plant may produce up to 60,000 seeds.
Similar Species: Curly dock (Rumex crispus) is a more widely distributed weed that is less tolerant of acid soil conditions. It is distinguished by relatively narrow curly-margined leaves, and membranous wings (sepals on fruits) that are not prominently toothed. At the seedling stage, the cotyledons of curly dock are longer and narrower than those of broadleaf dock. Common burdock (Arctium minus) also has broad leaves, but they are much larger, with hollow petioles, and a furry grey-green lower surface.
Biology: Seeds produced from a given plant vary greatly in their requirements for germination, which results in intermittent emergence in both spring and fall. Soil disturbance stimulates germination by exposing previously buried seeds to light and fluctuating temperatures, which are requirements for germination. Flower stalks are produced after about 35 days and regrowth from rootstocks is possible after about 50 days. Shoot regeneration occurs from shoot buds on the upper 3 inches of the taproot. Plants emerging in fall form a rosette that overwinters, whereas plants emerging in spring can flower within 9 weeks and set seeds the first year. Broadleaf dock does not tolerate competition well, and if crowded will delay flowering until the second or third year. In Ohio, flowers generally appear during June and July. The plant's longevity is variable: some die after flowering and others live 3 to 5 years. The seeds are adapted for dispersal by wind, water, and animals. Winged sepals, made of cork-like tissue, are thought to aid in dispersal by allowing the fruit to move long distances by wind and to float along streams. The toothed wings allow the seeds to adhere to animals and machinery. In a buried seed study, 94% of seeds germinated after 3 years and 83% after 21 years. Seeds survive passage through digestive tracts of cattle and many birds (but not chickens). This weed is very commonly associated with moist situations; improved drainage has been suggested as an aid to management. It does not tolerate tillage, especially if it occurs within the first month and a half of growth or if the upper part of the taproot is destroyed.
Toxicity: Leaves may cause mild dermatitis in some individuals. These plants have been used as a laxative, astringent, and in cooking. The plants are generally not considered poisonous, however curly dock seeds are reported as being toxic to chickens. Cattle and horses can become ill if large quantities of leaves are consumed.
Facts and Folklore:
- The young leaves have been eaten as greens, but they become bitter early in the growing season. They may also have a laxative effect.
- Broadleaf dock leaves have been used to soothe burns, blisters, and nettle stings. A tea prepared from the root was thought to cure boils.
- An old name for broadleaf dock is 'butter dock' which derives from the use of the leaves to wrap butter for market.