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Philadelphus microphyllus var. argyrocalyx
(Silvercup philadelphus)

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

Family: Hydrangeaceae

Scientific Name: Philadelphus microphyllus var. argyrocalyx (Wooton) Henrickson

Synonyms: Philadelphus argyrocalyx Wooton; Philadelphus serpyllifolius var. argyrocalyx (Wooton) M.E. Jones; Philadelphus ellipticus Rydberg; Philadelphus microphyllus subsp. argyrocalyx (Wooton) C.L. Hitchcock; Philadelphus wootonii Hu

Vernacular Name: Silvercup philadelphus

R-E-D Code: 1-1-3

Description: Erect shrub 1-2 m tall; leaves opposite, ovate, ovate-lanceolate or narrowly elliptic, margins entire, 10-35 mm long, 4-17 mm wide, glabrous or glabrescent above, sparsely villous hairy below, petiole about 2 mm long; flowers usually solitary (rarely 2 or 3) at the end of a short shoot 2-4 cm long with 2-4 pairs of leaves; calyx tube forming a cup (hypanthium); pedicels, hypanthia and sepals covered in dense tomentum of short, woolly hairs and longer, straight hairs; sepals 4; petals 4, white, 1.2-2.2 cm long, 0.7-1.8 cm wide; corolla cruciform, 2.2-4.2 cm across; stamens about 55, filaments fused into bundles; style and hypanthium disk glabrous; each seed long-tailed. Flowers June to August.

Similar Species: The hypanthium and sepals of Philadelphus microphyllus var. microphyllus are glabrous or only sparsely hairy at the base.

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

Habitat: Mountain slopes of usually sedimentary rock in piƱon-juniper woodland and lower montane coniferous forest; 2,100-2,600 m (6,900-8,500 ft).

Remarks: Endemic to the mountains of south-central New Mexico, but relatively common within this limited range. It is a handsome shrub with potential for ornamental use.

Conservation Considerations: This plant is not significantly threatened by the land uses within its habitats. Its response to forest fire has not been studied.

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.

Henrickson, J. 2007. New combinations in Philadelphus (Philadelphaceae). Journal of the Botanical Research Institute of Texas 1(2):901.

Information Compiled By: Robert Sivinski, 1999; last updated 2008

Agency Status:
Taxon USFWS State of NM USFS BLM Navajo Nation Natural Heritage NM Global Rank
Philadelphus microphyllus var. argyrocalyxPhiladelphus microphyllus var. argyrocalyx...S3

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