This plant consisted of aerial, isotomously and anisotomously branching stems that reached 12 mm in diameter and 40 cm in length.

[4] The possibly procumbent aerial stems arose from a leaf-less rhizome which bore smaller-diameter, positively geotropic root-like branches.

[7] The xylem or conducting tissue at the center of the aerial stems is distinctly star-shaped in cross-section and has been considered an early actinostele or an "Asteroxylon-type" protostele.

[10] "Sporangia, consisting of two kidney-shaped valves, are interspersed among the nonvascularized leaflike appendages and attached to the axis with a short pedicel.

A 2021 reanalysis found that Asteroxylon was more closely related to crown lycophytes than the more basal zosterophylls and Nothia.