Ageratum conyzoides L. is an invasive alien species, annual herb belongs to Asteraceae family Morphological and anatomical features of A. conyzoides accessions collected from four different regions of Tamil nadu, India to understand the adoptive mechanism and invasiveness of the species in various geographical conditions. Adult plant specimens of A. conyzoides were collected from 1.Coromandel coast (plain and agricultural field); 2.Pachaimalai (moderate altitude); 3.JawaduHills (excessive rainfall), and 4.Gudalur (high altitude),) in Tamil nadu, India. The plant species generally it is erect branching some times prostrate and it grows to approximately 2-5 ft. in height in Pachaimalai and 1-3 ft from Coromandel coast. The flowers are small, pretty at the top of its hairy stems. The inflorescence is pale purple and white head, respectively for Jawadhu hills and Coromandel coast and flowers are less than 6 mm across and arrange in close terminal corymbs of 8-15 heads. Anatomical features of node and internode of the stem of A. conyzoides shows following arrangement of the tissue from periphery towards center. Outer most layer, single cell layered thick, compactly arranged, without any intercellular spaces, rectangular outline, thick walled; outer surface cuticularized.