black root

noun

Definition of black root

  1. 1 :  any of several plants or their dark-colored roots: such as a :  a perennial plant (Pterocaulon undulatus) of the southern U.S. that has large black rootstocks b :  culver's root c :  colicroot 1 d :  a common comfrey (Symphytum officinale) with the upper part of the stem and inflorescence densely hispid

  2. 2 :  any of several plant diseases characterized by dark discoloration of roots: such as a :  cotton wilt 1 b :  a disease of radishes, beets, and sugar beets caused by fungi (genus Aphanomyces) and producing brown or black lesions on the roots, deformation of the roots, and a damping off of seedlings

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