Taxonomy
The Solanum nigrum species is a highly variable taxon with many varieties and forms described. There are two recognized subspecies:
1. S. nigrum L. subsp. nigrum — glabrous to slightly hairy with appressed non-glandular hairs
2. S. nigrum L. subsp. schultesii (Opiz) Wessley — densely hairy with patent, glandular hairs
The Solanum nigrum complex — also known as Solanum L. section Solanum — is the group of black nightshade species; characterized by their lack of prickles and stellate hairs, their white flowers and their green or black fruits arranged in an umbelliform fashion. The Solanum species in this group can be taxonomically confused, more-so by intermediate forms and hybridization between the species. Some of the major species within the Solanum nigrum complex are: Solanum nigrum, S. americanum, S. douglasii, S. opacum, S. ptychanthum, S.retroflexum, S. sarrachoides, S. scabrum, and S. villosum.
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