Orobanche multiflora

Plants simple or few-branched, 7–27 cm, relatively slender, base usually not enlarged. Roots usually inconspicuous, slender, unbranched or branched. Leaves numerous, appressed; blade lanceolate or broadly triangular, 3–10 mm, margins entire, sometimes ciliate, apex acute, surfaces glabrous. Inflorescences racemes, sometimes thyrsoid, pale yellow, white, or tan proximally, purple or pale lavender distally, sometimes branched, densely glandular-pubescent, appearing whitish or canescent, sometimes with axillary branches; flowers numerous; bracts erect to reflexed, ± lanceolate, 11–20 mm, apex acute or acuminate, densely glandular-pubescent. Pedicels 0–5 mm, much shorter than plant axis; bracteoles 2. Flowers: calyx pallid externally, purple internally, weakly bilaterally symmetric, 15–21 mm, deeply divided into 5 lobes, lobes lanceolate-attenuate, densely glandular-pubescent; corolla 22–36 mm, tube white to pallid or cream, sometimes pinkish or light purplish tinged, rarely light yellow distally, sometimes with purple veins, constricted above ovary, only slightly bent forward, densely pubescent; palatal folds prominent, yellow, densely pubescent; lips externally white to pallid or cream, sometimes pinkish or light purplish tinged, internally pink or purple, sometimes white with purple veins, rarely light yellow, abaxial lip spreading, 5–9 mm, lobes broadly lanceolate, apex obtuse or rounded, adaxial lip erect or reflexed, 6–12 mm, lobes oblong, apex rounded; filaments pilose with ring of hairs at insertion, anthers included, woolly. Capsules ovoid, 8–12 mm. Seeds 0.4–0.5 mm. 2n = 48.

Phenology: Flowering Aug–Sep.
Habitat: Arid grasslands, semideserts, open woodlands.
Elevation: 0–2500 m.

Colo., N.Mex., Tex.

Discussion

Orobanche multiflora is parasitic mainly on Gutierrezia and occasionally Heterotheca (Asteraceae). A population in southern Texas is parasitic on Varilla texana (Asteraceae).

There is considerable confusion about what constitutes Orobanche multiflora. It has been interpreted as both a variety and subspecies of O. ludoviciana. The much larger flowers (22–36 mm versus 14–20 mm) set it apart from O. ludoviciana. P. A. Munz (1930) described four varieties of O. multiflora: vars. arenosa, multiflora (as typica), pringlei, and xanthocroa. Variety xanthocroa was based on a specimen of Conopholis. Variety arenosa is treated in synonymy under O. ludoviciana. Variety pringlei was based on a few specimens from northeastern Mexico that appear to represent an undescribed species.

The distribution range is not well defined in the literature. The authors consider Orobanche multiflora to have a much more restricted range than previously indicated, occurring mostly in Colorado, New Mexico, and adjacent northwestern Texas, with disjunct populations in southern Texas that are apparently this species. Specimen data indicate that the species distribution is most likely east of the Continental Divide; plants from west of the continental divide with this binomial are probably misidentified.

Plants from five counties in extreme southern Texas, near the Mexican border, appear to be a disjunct variant of Orobanche multiflora that flowers in spring. The flowers are about the same length, but the corolla tube is much narrower. Margins of the petals are often undulate and are an unusual shade of blue-purple. The pubescence at the base of the filaments is also reduced. Host and habitat differences also raise questions about the classification of these plants.

Selected References

None.

Lower Taxa