Isothecium myosuroides has a distinctly tree-like growth form, its main stems growing away from the substrate, unbranched in the lower part, and bushily branched above. It often occurs in pure, dense mats, so its tree-like form may not be immediately apparent. It often grows on inclined or vertical surfaces, with the stems and branches curving downwards. Shoots are typically 1 to 2 cm tall. Stem leaves, especially towards the base of the stem, are about 2 mm long, broadly egg-shaped to triangular with a heart-shaped base, rapidly contracting to a finely tapering tip. Branch leaves are 1 to 1.5 mm long, narrower, triangularly spearhead-shaped, and taper to a shorter but still slender, rather sharply toothed tip. The single nerve ceases above mid-leaf. Capsules are 2 to 2.5 mm long, frequent in some regions, elliptical, slightly asymmetrical and inclined. The lid has a long beak.

It grows on boulders and tree trunks in woodland and shaded places, but may occur in the open. It does not grow on strongly base-rich rocks such as limestone. It is abundant in rocky, upland woods on siliceous and non-calcareous substrates, and in western areas may dominate trunks of oak and other trees.

All year round.

Widespread and fairly frequent in Britain.

Fairly frequent in Leicestershire and Rutland.