The leaves of Spaerth's alder are ovoid, pointed and up to 16 cm (6.3 in) long. The underside of the leaf is matt green and brighter than the top. The leaf margin is serrated.
The male flowers (catkins) are conspicuous, about 10 cm (3.9 in) long and often hang on to fourth in a clump. The female flowers are inconspicuous.
Small woody cones, first green then dark brown.
Young twigs are gray-green, the older brown-green with many lenticels.
single tree, planting in groups. Urban green, street tree