A shrub 10 to 12 ft high, or occasionally a small tree; young shoots four-sided and four-winged, slightly warted, not downy. Leaves 2 to 5 in. long; leaflets commonly five, but varying from three to nine, obovate or oval, tapered at the base, rounded or hardly pointed at the apex, 1⁄2 to 11⁄4 in. long, toothed except at the lowest third (sometimes quite entire), glabrous on both surfaces; main leaf-stalk grooved above; the terminal leaflet rather long-stalked, the uppermost pair stalkless, those below more or less stalked. Flowers produced from the joints of the previous year’s wood in panicles 2 to 4 in. long. Petals two, broad-elliptic to roundish, about 1⁄4 in. long. Fruits about 1 in. long, 1⁄4 in. wide, with a notched tip.
Native mainly of California, where it was discovered by David Douglas, but found occasionally farther inland and extending southward into the Mexican State of Baja California. It was not introduced until 1879, when Prof. Sargent sent it to Kew. The small tree there did not flower and was sometimes injured at the tips by frost. This plant no longer exists, and a replacement has proved to be wrongly named.
F. dipetala appears to be one of the most ornamental of the ashes in flower, but would perhaps thrive better in eastern England than at Kew. Although it bears flowers with petals, it is not a member of the section Ornus, from which it is clearly distinguished by its inflorescences, which are produced from leafless axillary buds as in section Fraxinus (Fraxinaster), to which it belongs as the only member of the subsection Dipetalae.