Alnus × spaethii Callier

A hybrid between A. japonica and A. subcordata which originated at the Späth nurseries of Berlin in 1894 and spread to the trade in 1908. It is a distinctive tree with a uniformly upright, ovate crown to 20 m or more, and newly emerging leaves which are violet-purple. As noted briefly in the reprint (REFERENCE) this hybrid was highly rated in trials held at Boskoop in Holland (Dendroflora, No. 9 (1972), pp. 7–9). It makes a fast-growing amenity and street tree capable of attaining a height of about 15 m in fifteen years. It is best grown in wetter conditions but can tolerate drought as well. The two examples at Kew by the lake were received from Späth in 1909. It is not uncommon in cultivation with the largest found at Borde Hill (26 m), Maurice Mason’s garden and Ryston Hall, Norfolk (Tree Register 2020).