CPC Plant Profile: Arizona Rabbitbrush
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Plant Profile

Arizona Rabbitbrush (Chrysothamnus molestus)

A view of this shrub in flower in its rocky habitat. Photo Credit: Joyce Maschinski
Description
  • Global Rank: G3 - Vulnerable
  • Legal Status: N/A
  • Family: Asteraceae
  • State: AZ
  • Nature Serve ID: 129740
  • Date Inducted in National Collection: 04/04/1991

C. molestus is a perennial prostrate shrub or sub-shrub that is found only on the Coconino Plateau in northern Arizona. It produces profuse yellow rayless flowers in the fall and can be distinguished from common rabbitbrush by its hairy leaves which are less than 2mm wide. (Cobb et al. 1996) Cobb and colleagues (1996) have done extensive research on the impact of fire on this species and determined that the season of the burn determines how it impacts the plants. While adult plants benefit from fall burns, seedling establishment is heavily reduced. In the spring, the trend is reversed, with seedling establishment improving and adults plants suffering.

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Updates
  • 09/07/2020
  • Propagation Research

In 1991, The Arboretum at Flagstaff conducted germination trials. Germination was maximized after 4 months of cold stratification (56%), but seeds could germinate over a broad range of treatments including varying day/night temperatures (26%), 2 and 3 month cold stratification (48%). We would expect that wild populations could have two bouts of germination, one in the fall and one in the spring. Cobb et al. (1996) examined the effects of fall and spring prescribed burning on C. molestus. They found fall burns enhanced growth of mature plants, but reduced seedling establishment 12-fold. Conversely, spring burns caused 25% mortality of adult plants and 3-fold reduction in volume. They recommend fall burns, but not in a year when seedlings are beginning to establish.

Nature Serve Biotics
  • 05/02/2017

Chrysothamnus molestus is extant at 21 locations within Coconino County, Arizona, zero to few of which are protected.(Fed. Register 95-06-30)

Joyce Maschinski, Ph.D.
  • 01/01/2010

Cobb et al. 1996 listed threats to this species as: grazing by wild and domestic ungulates low recruitment in natural populations

Joyce Maschinski, Ph.D.
  • 01/01/2010

Chrysothamnus molestus is extant at 21 locations within Coconino County, Arizona, only a few may be protected. (NatureServe Explorer 2001)

Joyce Maschinski, Ph.D.
  • 01/01/2010

In 1991, The Arboretum at Flagstaff conducted germination trials. Germination was maximized after 4 months of cold stratification (56%), but seeds could germinate over a broad range of treatments including varying day/night temperatures (26%), 2 and 3 month cold stratification (48%). We would expect that wild populations could have two bouts of germination, one in the fall and one in the spring. Cobb et al. (1996) examined the effects of fall and spring prescribed burning on C. molestus. They found fall burns enhanced growth of mature plants, but reduced seedling establishment 12-fold. Conversely, spring burns caused 25% mortality of adult plants and 3-fold reduction in volume. They recommend fall burns, but not in a year when seedlings are beginning to establish.

Joyce Maschinski, Ph.D.
  • 01/01/2010

None known.

Joyce Maschinski, Ph.D.
  • 01/01/2010

Continue research to understand why recruitment is low in natural populations, understand the role of disturbance in seedling establishment. Also, undertake research to understand the significance of asexual reproduction as a potential inhibitor of range expansion. Implement research findings to manage the habitat in the most beneficial way.

Joyce Maschinski, Ph.D.
  • 01/01/2010

Continued germination trials.

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Photos
Nomenclature
Taxon Chrysothamnus molestus
Authority (S.F. Blake) L.C. Anderson
Family Asteraceae
CPC Number 939
ITIS 501519
USDA CHMO2
Common Names Arizona rabbit-brush | Tusayan rabbit-brush | stickyfruit low rabbitbrush
Associated Scientific Names Chrysothamnus molestus | Ericameria molesta | Chrysothamnus viscidiflorus var. molestus
Distribution Patchily distributed on limestone-derived soils in Coconino County Arizona (Cobb et al. 1996).
State Rank
State State Rank
Arizona S3
Habitat

This species is typically found in open pinyon-juniper grasslands where periodic natural fires naturally occur at an interval of every 15 to 30 years (Cobb et al. 1996).

Ecological Relationships

This species is not fire-dependent, but is tolerant of prescribed burns after the growing season. (Cobb et al. 1996)

Pollinators
Common Name Name in Text Association Type Source InteractionID
Reintroduction
Lead Institution State Reintroduction Type Year of First Outplanting

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