University of Maryland Extension

Weed of the Week - Broadleaf Dock

Chuck Schuster

Warm weather has certainly settled upon us this week. I observed a landscape management crew out working in the beds preparing them for the war on weeds and was pleased to see that the mulch had been pulled back and that the pre-emergent herbicide was being applied below the mulch. This will provide a great deterrent to weed growth. Coupled with an appropriate mulch (it was ready to go down after the application of herbicide) season long weed free landscape beds will be appreciated by all.

Broadleaf Dock, Rumex obtusifolius, is showing itself currently in many landscape and turf settings. Also known as Broad-leaved Dock, Bitter Dock, Bluntleaf Dock, Dock Leaf or ButterDock.I came across a very showy patch during a recent outing in Howard County. This perennial weed, very similar to Curly Dock, will have a yellow to orange colored taproot, for a large basal rosette, and produce a single upright stem that can reach a height of more than forty inches. Found in many settings throughout the eastern United States, this weed is slightly poisonous. The milky sap can also cause dermatitis or blistering of the skin. The leaves have a slightly wavy edge, the lower leaves will appear with a petiole, and will have a red vein. Leaves will become smaller progressively as they are produced up the flowering stalk or stem. The flower stem will be a reddish brown color, and it will be ribbed. The flowers will occur in clusters of racemes on the upper one third of the flower stalk and will have green sepals that, as they mature, turn to a reddish brown. The seeds will be a reddish brown in color also. The seeds will have a serrated edge and will blow in the wind or be caught on clothing or animal hair and transported. The seeds can remain viable for many years.

This perennial weed is difficult to control. When working in landscape settings, Snapshot (trifluralin and Isoxaben) and Gallery (Isoxaben) have been shown to provide good control. Post emergent landscape will require products that include Burnout (Vinegar) glyphosate, clopyalid (Lontrel ), and fatty acid soaps. In turf the use of 2, 4D or Dicamba have worked very well. Always remember that glyphosate use near roots, or plant stem/trunks can lead to desired plant damage. 2,4D and Dicamba can volatilize and damage many species of trees and shrubs. Use proper care when using these products.

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