Rumex obtusifolius is easily recognizable by its very large leaves, some of the lower leaves having red stems. The edges of the leaves are slightly "crisped" or wavy. The foliage of the plant can grow to about 18 inches in height. The stems have nodes covered by an ocrea, a thin, paper-like membrane - a characteristic of the Polygonaceae family.
Large clusters of racemes contain green flowers that change to red as they mature. They are held on a single stalk that grows above the leaves and blooms June through September. The seeds produced are reddish-brown.
Seedlings can be identified by the oval leaves with red stems and rolled leaves sprouting from the center of the plant.
Rumex crispus - curly dock - is very similar in appearance but with thinner and wavier leaves. In more detail, the calyx of curly dock has smooth margins while the calyx of broadleaf dock has horned margins.
The 'milk' of the dock leaf is known to contain tannins and oxalic acid, which is an astringent. A tincture of dock is helpful for problems of the menopause. According to folk remedies, dock root has a pronounced detoxing effect on the liver and it cleanses the skin.
Broadleaf dock is considered a weed and is slightly poisonous. It is designated an "injurious weed" under the UK Weeds Act 1959 Livestock have been known to get sick after feeding on it. But eradicating the plants is difficult. The perennial plant can have a deep taproot reaching 5 feet down. Also, the milk of the plant has been known to cause mild dermatitis.
Seeds have toothed wing structures, allowing them to be dispersed by wind or water, and also allow them to attach to animals or machinery to be spread great distances. They can lie dormant for years before germination, making vigilant pulling or tilling essential.
First year plants can seed, making early detection important for eradication.
The main weaknesses of Broadleaf are its poor competition, crowding causes flowering to be delayed for up to three years, and its susceptibility to disturbance. Frequent tilling will disrupt roots and kill seedlings and even older plants. The plant also thrives in moist environments and improved drainage can also help control its growth.