An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified. The modifications can involve the length and the nature of the Internodes and the phyllotaxis, as well as variations in the proportions, compressions, swellings, adnations, connations and reduction of main and secondary axes. Inflorescence can also be defined as the reproductive portion of a plant that bears a cluster of flowers in a specific pattern.
The stem holding the whole inflorescence is called a peduncle and the main stem holding the flowers or more branches within the inflorescence is called the rachis. The stalk of each single flower is called a pedicel.
Verbena bonariensis (Purpletop vervain, Tall verbena, Clustertop vervain, or Pretty verbena) is a member of the verbenafamily cultivated as a flowering annual or herbaceousperennial plant. In USA horticulture, it is also known by the ambiguous names "purpletop" (also used for the grassTridens flavus) and "South American vervain" (which can mean any of the numerous species in the genusVerbena occurring in that continent). For the misapplication "Brazilian verbena" see below.
It is native to tropical South America where it grows throughout most of the warm regions, from Colombia and Brazil to Argentina and Chile.