An undated herbarium specimen from Haarlem showing a hybrid cultivar labelled "U. × hollandica 'Superba' Rehd., received as U. praestans from Späth, Berlin" (see 'External links') matches Henry's description of Späth's tree planted in 1900 at Kew.
A specimen from Haarlem's herbarium, undated but featuring a hybrid cultivar identified as "U. × hollandica 'Superba' Rehd., was received from Berlin by Späth and is consistent with Henry's account of the tree planted in 1900 at Kew.