Nuttallia rhizomata
Author: Reveal

Roan Cliffs blazing star

Loasaceae (Blazingstar Family)

Close up of Nuttallia rhizomata by Susan Spackman Panjabi
Click image to enlarge.

Taxonomic Comments

Reveal (2002) determined that the plants formerly thought to be Mentzelia argillosa in Colorado are distinct from the plants in Utah, and named the Colorado plants M. rhizomata (Utah plants are M. argillosa). In the PLANTS database the plants from both states are still listed as M. argillosa (NRCS 2013). Weber and Wittmann (2012) call this taxon Nuttallia rhizomata. Ackerfileld (2012) lists as Mentzelia rhizomata.

Ranks and Status

Global rank: G2
State rank: S2
Federal protection status: BLM Sensitive
State protection status: None

[+] Description and Phenology

Nuttallia rhizomata by Kathy Cranmer. Please also see 1997 profile.
Click image to enlarge.

General description: Plants are low, sprawling, rhizomatous, long-lived herbaceous perennials forming discrete clumps 1-2.5 × 1-3.5 dm with numerous, twisted and often tangled, exceedingly fragile and easily detached caudex branches (0.5-)0.8-3 dm long arising at irregular points along a horizontally spreading, elongate, infrequently branched, woody, deeply seated underground, entirely smooth rhizome up to 1 m or more in length.  Stems are widely spreading and becoming curved-ascending, flexuous, but often erect in early anthesis, slender, flexuous, freely branched, the epidermis white and papery, scabrous-puberulent with a mixture of pointed scabrid hairs and pagodiform, glochidiate hairs, the larger and longer hairs tapering to a slightly expanded base, the shaft of the scabrid hairs smooth or minutely rugose with the glochidiate ones finely retrorse, the pubescence becoming more dense and the hairs somewhat longer on the upper branches.  Leaves are all cauline and well distributed along the stems, alternate, sessile, light green, narrowly lanceolate, lanceolate, narrowly elliptic or obovate, entire or shallowly undulate-dentate with 2-4 rounded to obtuse lobes on each side, 1.5-4(-4.5) × (0.2-)0.3-1.2(-1.5) cm, scabrous-puberulent on both surfaces with longer and more dense hairs near the base, acute to obtuse apically, tapering basally, the margins often minutely ciliated with glochidiate hairs; inflorescences with 1-few flowers atop each side branch.  Flowers are perfect, golden-yellow to yellow, the pedicel 1-3 mm long, subtended by two opposite, linear to narrowly lanceolate, foliaceous bracts, (8-)10-17(-20) × (0.8-)1-2.5 mm, these gradually deciduous in fruit; sepals 5, lanceolate, persistent, erect in bud, becoming strongly reflexed at anthesis but spreading in fruit, (4-)5-8(-11) mm long, scabrous abaxially with upwardly curved hairs, finely so with numerous, long, slender, appressed hairs adaxially; petals 5, glabrous, (9-)10-15 × 6-10 mm, broadly spatulate to broadly obovate and slightly clawed, obtuse to rounded apically; filaments yellow, numerous, glabrous, the two whorls of five petaloid filaments each typically cuspidate and frequently bearing an anther, slightly shorter and narrower than the petals, those of the first whorl rhombic and distinctly clawed, 7-9 × 5-6 mm, those of the second whorl oblanceolate to narrowly oblanceolate, 6-8 × (1.5-)3-4 mm, the remaining whorls of 35-60 or more filaments linear, (1.8-)2-4(-4.5) mm long; anthers anthers pale yellow, (1-)1.2-1.7(-2) mm long, oblong; style early deciduous, erect, slender, 5.5-7 mm long, the stigma minutely 3-lobed.  Fruit is a dried capsule, (5-)8-10(-13) × (5-)6-8(-10) mm, urceolate, scabrous-puberulent, rounded basally, opening as an ever-widening apical pore where the stigma was positioned; seeds 15-20 per capsule, oblong, flat, 2-3 × 1.6-2.2 mm, brownish-green, smooth and somewhat shiny, slightly winged, the surface cells with 8 to several papillae (Reveal 2002).

Look Alikes: Mentzelia rhizomata is a long-lived perennial (rather than a biennial) and is unique among all members of the genus in having a rhizome (Reveal 2002).

Phenology: The plants flower in June and August and set fruit from mid August until late September. Flowers are fully open only in the afternoon. Seeds are rapidly dispersed soon after reaching maturity (Reveal 2002). Plants have also been observed to flower in September during an unusually wet year (Colorado Natural Heritage Program 2013).

[+] Habitat

Habitat of Nuttallia rhizomata by Susan Spackman Panjabi
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Known only from steep, shaley talus slopes derived from the Parachute Creek Member of the Green River Formation (Holmgren and Holmgren 2002, Reveal 2002).  The plants are commonly associated with Gambel oak, western chokecherry, mountain mahogany and Utah juniper (Reveal 2002).

Elevation Range: 5,243 - 9,186 feet (1,598 - 2,800 meters)

[+] Distribution

Distribution of Nuttallia rhizomata in Colorado.
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Colorado endemic: Yes
Global range: Endemic to Colorado; known from the Roan Plateau in Garfield County. Estimated range is 1,365 square kilometers (527 square miles), calculated in GIS by drawing a minimum convex polygon around the known occurrences (estimated by the Colorado Natural Heritage Program in 2008).

[+] Threats and Management Issues

Summary results of an analysis of the status of Nuttallia rhizomata based on several ranking factors. This species was concluded to be “weakly conserved”. From Rondeau et al. 2011.
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Oil and gas development and mining oil shale are possible threats for most of the known occurrences. Many of the occurrences are on private land owned by oil companies, and the remaining are on BLM lands which are also leased for mining activities.

[+] References

    • Elliott, B. A., S. Spackman Panjabi, B. Kurzel, B. Neely, R. Rondeau, M. Ewing. 2009. Recommended Best Management Practices for Plants of Concern. Practices developed to reduce the impacts of oil and gas development activities to plants of concern. Unpublished report prepared by the Rare Plant Conservation Initiative for the National Fish and Wildlife Foundation.
    • Holmgren., N. H. and P. K. Holmgren. 2002. New Mentzelias (Loasaceae) from the Intermountain region of western United States. Systematic Botany 27(4): 747-762.
    • Neely, B., S. Panjabi, E. Lane, P. Lewis, C. Dawson, A. Kratz, B. Kurzel, T. Hogan, J. Handwerk, S. Krishnan, J. Neale, and N. Ripley. 2009. Colorado Rare Plant Conservation Strategy, Developed by the Colorado Rare Plant conservation Initiative. The Nature Conservancy, Boulder, Colorado, 117 pp.
    • O'Kane, S. L. 1988. Colorado's Rare Flora. Great Basin Naturalist. 48(4):434-484.
    • Reveal, J.L. 2002. Mentzelia rhizomata (Loasaceae: Mentzelioideae), a new species from western Colorado. Systematic Botany 27(4):763-767.
    • Rondeau, R., K. Decker, J. Handwerk, J. Siemers, L. Grunau, and C. Pague. 2011. The state of Colorado's biodiversity 2011. Prepared for The Nature Conservancy. Colorado Natural Heritage Program, Colorado State University, Fort Collins, Colorado.
    • Weber, W.A., and R.C. Wittmann. 2012b. Colorado Flora, Western Slope, a field guide to the vascular plants, fourth edition. Boulder, Colorado. 532 pp.
    • Welsh, S.L. 1979. Status report for Mentzelia argillosa. Unpublished report prepared for the Colorado Natural Areas Program, Denver, CO.
    • Welsh, S.L., N.D. Atwood, S. Goodrich, and L.C. Higgins (eds.) 1993. A Utah flora. 2nd edition. Brigham Young Univ., Provo, Utah. 986 pp.

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