[4] B. americana is a trioecious shrub, 2–5 m tall with light brown fissured bark.

The young branches are sub quadrangular, and tomentose, bearing leaves which vary greatly in size, shape and indumentum.

The flowers are borne in cymules, the short (< 2.5 mm) corollas yellow inside and white outside.

Unlike many American species of Buddleja, which are often diploid, B. americana is tetraploid (2n = 76).

[3] The species is not cold hardy, and quickly killed by temperatures only marginally below freezing.