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A deciduous small tree with slender young shoots of a pale yellowish grey at first, becoming shining pale grey with age, thickly covered with small warts, not downy. Leaves trifoliolate, the leaflets of lanceolate shape, faintly round-toothed, stalkless, slenderly pointed or bluntish, the side ones oblique at the base, 13⁄4 to 31⁄2 in. long, 3⁄8 to 7⁄8 in. wide; shining green above, dull beneath, quite glabrous on both surfaces; main-stalk 1 to 2 in. long. Fruits elm-like, but occasionally two-or even three-winged, 3⁄4 to 1 in. wide, wrinkled, notched at the top, glandular in the centre; seed flattish, oval.
Native of the Grand Canyon, Arizona. There was a small tree at Kew about 10 ft high which was raised from seed received from the Arnold Arboretum in 1914 as “P. angustifolia”, which I believe to be P. lutescens. Dr Rehder collected this species on the Bright Angel Trail of the Grand Canyon in 1914 and it is probably from the seed he gathered then that this tree was raised. Another site for the species in the Grand Canyon is the Red Canyon Trail, where it was collected by Lester F. Ward in 1901 and distributed as “P. angustifolia”. P. lutescens has the same odour as the well-known P. trifoliata and the leaves are thickly sprinkled with oil glands that show transparently when the leaf is held up to the light and examined through a lens. It is very distinct from the older species in its narrow lanceolate leaves.