A deciduous, rounded bush 8 ft or more high; young shoots slightly downy. Leaves oval or obovate, 2 to 4 in. long, 3⁄4 to 11⁄2 in. wide, tapering at the base, often rounded at the apex; upper surface glossy green and furnished with scattered hairs, lower surface pale, rather glaucous, downy (at least when young); stalk downy, 1⁄4 in. or less long. Flowers fragrant, white with a blotch of yellow on the upper side, 21⁄2 to 3 in. across, produced in terminal clusters of six to twelve after the leaves, during June and July. Calyx-lobes up to 3⁄16 in. long, ciliate. Corolla-tube 1 in. or more long, downy; stamens and style protruded, 2 to 21⁄2 in. long. Bot. Mag., t. 5005. (s. Azalea ss. Luteum)
Native of western N. America; introduced by Wm Lobb for Messrs Veitch about 1851. This beautiful azalea is the only species of its section found west of the Rocky Mountains. It has many points of resemblance to, and appears to be the Western representative of, R. arborescens, but has larger yellow-blotched flowers and its foliage is quite hairy beneath; the calyx also is shorter. It does not blossom until the great azalea season is over, or until it is itself in almost full leaf. It is one of the best summer-flowering shrubs, although it has taken horticulturists a long time to find that out. In 1857, Lindley, then the high priest of gardening, pronounced it to be 'of little value'. Anthony Waterer of Knap Hill and Koster of Boskoop, by crossing it with the bright-coloured azaleas that flower earlier, laid the foundation of a beautiful race of late-flowering varieties. See further in the section on hybrids, p. 914.