Mearns’s mock orange Mearns’s mock orange

Philadelphus hitchcockianus S. Y. Hu; P. mearnsii subsp. bifidus C. L. Hitchcock

Shrubs, 5–15(–40) dm. Stems tan-brown, weathering gray, striate, stiffly divaricately branched, strigose-sericeous; internodes 0.1–3.5 cm; short shoots often present; axillary buds exposed. Leaves: petiole 0.5–4 mm; blade green or gray-green abaxially and adaxially, oblong-lanceolate, linear-lanceolate, or elliptic to ovate, 0.5–1.7(–3) × 0.1–0.6(–1.1) cm, coriaceous, margins entire, ± revolute, surfaces ± equally moderately strigose, hairs appressed, coarse, 0.2–0.6(–0.9) mm, without understory of coiled-crisped hairs; veins inconspicuous. Inflorescences: flowers solitary, produced from previous year's long shoots, often appearing axillary. Pedicels 0.5–2 mm. Flowers: hypanthium sparsely to moderately strigose-sericeous or glabrous; sepals ovate-lanceolate, 2–3.5(–4.2) × 1.3–2.3 mm, apex acute to acuminate-caudate, abaxial surface sparsely to moderately strigose-sericeous or glabrous, adaxial surface glabrous except villous along distal margins; petals white, oblong-lanceolate to broadly oblong-ovate, (5–)7–8.5(–10) × 2.5–4.5(–5.8) mm; stamens 13–18(–24); filaments distinct, 1.3–4 mm; style 1, clavate, 2–3.2 mm, narrow base 0.5–1.5 mm; stigmatic portion 1.3–2 mm, distally lobed to 0.5 mm. Capsules ovoid-turbinate, 3–5.5 × 3.2–5.5 mm, sepals ± persistent at distal 1/3 or more distally, capsule distal surface impressed in 4(–8) radial lines. Seeds not caudate, 1–1.2 mm.

Flowering Apr–Jun; fruiting May–Nov. Limestone mountains, oak-pinyon zones; 1300–1800(–2200) m; N.Mex., Tex.; Mexico (Coahuila).

Philadelphus hitchcockianus, with its hypanthium and abaxial sepal surfaces glabrous, is here synonymized with P. mearnsii, which has its hypanthium and abaxial sepal surfaces moderately sericeous-strigose; substantial variation in this character is found in several populations. Hu S. Y. (1954–1956) alleged that P. hitchcockianus and P. mearnsii also differ in fruit size; however, that character is variable and overlapping.