[4] The foliage consists of slender, much-branched green to grey-green twigs 0.8–1 mm (0.032–0.039 in) diameter, bearing minute scale-leaves in whorls of 9–11.

The fruit is an oval woody structure, superficially resembling a conifer cone made up of numerous carpels each containing a single seed with a small wing 4–5 mm (0.16–0.2 in) long.

[5] Unlike Casuarina equisetifolia, Mountain Ru (C. junghuhniana) has a narrower canopy, small and neat branches.

[4][6] Like some other species of the genus Casuarina, C. junghuhniana is an actinorhizal plant able to fix atmospheric nitrogen.

In contrast to species of the plant family Fabaceae (e.g., beans, alfalfa, Acacia), Casuarina harbours a symbiosis with a Frankia actinomycete.