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Philadelphus wootonii (Not NMRPTC Rare)
(Wooton's philadelphus)

[taxon report][distribution map][all photos][line drawing]



Family: Hydrangeaceae

Scientific Name: Philadelphus wootonii Hu

Synonyms: The NMRPTC considers Philadelphus wootonii Hu to be a synonym of Philadelphus microphyllus var. argyrocalyx (Wooton) C.L. Hitchcock

Vernacular Name: Wooton's philadelphus

R-E-D Code: 3-2-3

Description: Erect shrub 1-2 m tall; leaves opposite, ovate, ovate-lanceolate or narrowly elliptic, margins entire, 10-18 mm long, 5-9 mm wide, sparsely hairy above, sparsely villous hairy below, petioles about 2 mm long; flowers usually solitary at the end of a short branchlet; calyx tube forming a cup (hypanthium); hypanthium and sepals covered with lanate hairs; sepals 4; petals 4, ovate, white, 8 mm long, 6-7 mm wide; corolla disk-shaped (disciform), 2 cm across; stamens numerous; style bases and hypanthium disk pubescent; each seed short-tailed. Flowers June to August.

Similar Species: Philadelphus microphyllus var. argyrocalyx has cross-shaped (cruciform) flowers with ovate-oblong petals, the hypanthium disks and bases of the styles are glabrous, seeds longer-tailed, and the upper leaf surfaces glabrous or glabrescent. The hypanthia and sepals of P. microphyllus var. microphyllus are glabrous or only sparsely hairy at the base.


Distribution: New Mexico, southern Lincoln and northern Otero counties, Sacramento and White mountains.

Habitat: Mountain slopes in pion-juniper woodland and lower montane coniferous forest; 2,100-2,500 m (6,900-8,200 ft).

Remarks: Philadelphus wootonii is known only from the 1905 type collection (Gavilan Canyon, White Mountains) and one other (fruiting) specimen from near Cloudcroft. It was named by Hu (1954) in a monograph of the genus. The characters used by Hu to distinguish P. wootonii have shown to preserve unrealibly in pressed specimens, to vary with stages of plant growh, and to vary between plants in a single population. Bob Sivinski and Richard Worthington have both searched for P. wootonii in the vicinity of the two known specimens, but found only P. microphyllus var. argyrocalyx. Chris Frazier (1999) in a study of New Mexico Philadelphus found that many of Hu's characters and character states are unreliable for classifying New Mexico plants. With this information, the NMRPTC concluded at its 2005 annual meeting that P. wootonii is an insignificant variant of Philadelphus microphyllus var. argyrocalyx.

Conservation Considerations: Philadelphus wootonii is now included within Philadelphus microphyllus var. argyrocalyx, which is a New Mexico rare plant, but is not significantly threatened by the land uses within its habitats.

Important Literature (*Illustration):

Hu, S. 1954. A monograph of the genus Philadelphus. Journal of the Arnold Arboretum 37:15-90.

Frazier, C.K. 1999. A taxonomic study of Philadelphus (Hydrangeaceae) as it occurs in New Mexico. The New Mexico Botanist 13:1-6.

Information Compiled By: Robert Sivinski, 1999, last updated 2006


Photo credits in header Peniocereus greggii var. greggii © T. Todsen,
Lepidospartum burgessii © M. Howard, Argemone pleiacantha ssp. pinnatisecta © R. Sivinski
©2005 New Mexico Rare Plant Technical Council