Eucalyptus lehmannii is a sometimes multi-trunked
mallee with smooth bark which is whitish grey to grey-brown and orange-brown and which sheds in strips. The stems of young plants are initially triangular in cross-section with leaves that are alternate, oblong to elliptical or lance-shaped, 5–8 cm long and 1–3 cm wide, glossy green on the upper surface and dull blue-green below. Older stems are smooth and round with alternate leaves. The adult leaves have a
petiole 0.1–1.5 cm long and a blade elliptical to oval-shaped, about 4.5–9.5 cm long and 0.7–2.8 cm wide and both surfaces glossy light to mid-green. The oil glands in the leaves common to all eucalypts, are obscure or scattered. The
inflorescences appear in the
axils of the leaves, have a flattened stalk 4–11 cm which curves downwards as the flowers open. There may be 11–19 or more buds in each inflorescence, with their bases joined. By the time the bud opens, it is about 3.3–6.5 cm long, including the cap (strictly the
operculum) and 0.5–1.0 cm wide at the base of the cap. The stamens are erect and greenish-yellow. ==Taxonomy and naming==