Forms patches of 1 mm wide, yellowish green thalli that end in narrow gemma bearing branches which protrude from the substrate. The gemmae of this species are restricted to the very tip of these branches. Long dry specimens are unique in turning blue, hence its specific name. Sporophytes are rare.

Twigs and branches of deciduous trees, especially willow (Salix), but also old elders (Sambucus nigra) and young elms (Ulmus).

All year.

Common.

Uncommon.