CPC Plant Profile: Flagstaff False Pennyroyal
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Plant Profile

Flagstaff False Pennyroyal (Hedeoma diffusa)

Photo Credit: S Murray
Description
  • Global Rank: G3 - Vulnerable
  • Legal Status: N/A
  • Family: Lamiaceae
  • State: AZ
  • Nature Serve ID: 145864
  • Date Inducted in National Collection: 01/01/1985

Flagstaff pennyroyal is a small perennial herb which forms circular prostrate mats with numerous shoots. Its small leaves are arranged oppositely on delicate square stems. The small, irregular blue-lavender flowers can be found from late May to September, and are borne in clusters of 1-3 in leaf nodes. These flowers remain open for about 3 days, with fruit developing 2 to 3 weeks after pollination. Flowering occurs from late May through September. (Irving 1980)

Participating Institutions
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Updates
Sheila Murray
  • 10/11/2021
  • Seed Collection

CPC received a grant from the Institute for Museum and Library Services (IMLS) for a project entitled, “RNA integrity as a powerful metric of aging in preserved seed collections of wild rare plant species”, and as part of this grant The Arboretum at Flagstaff collected seeds for Hedeoma diffusa, or the Flagstaff Pennyroyal. We collected 500 seeds bulked together in October of 2021. These tiny fresh seeds will be compared to older seed we collected from the same population to find out how fast rare seeds are losing their viability in storage. The seed collecting conditions in 2021 were vastly superior to conditions in 2020, in which Northern Arizona experienced the worst drought in recorded history. Plants all across the ecosystem responded well to the shift back to a relatively normal amount of rainfall.

Center for Plant Conservation
  • 10/07/2021
  • Orthodox Seed Banking

In accordance with the CPC and USFS Rare Plant Seed Banking Agreement, in 2016, Sheila Murray from The Arboretum at Flagstaff made three separate collections of Hedeoma diffusa (Flagstaff false pennyroyal) from Coconino National Forest. Sheila made two large collections, consisting of over 50 maternal lines and 2000 seeds, and one smaller collect from just 5 maternal plants yielding 113 seeds. Seed collections with more than 300 seeds were divided and duplicated between The Arboretum at Flagstaff and the National Laboratory for Genetic Resources Preservation in Fort Collins, CO.

Center for Plant Conservation
  • 10/07/2021
  • Seed Collection

In a five-year collaboration between US Forest Service (USFS) and Center for Plant Conservation (CPC), rare plant populations located on Region 3 USFS land were identified, seed collectedand banked through CPC’s network of botanical gardens In 2016, Sheila Murray from The Arboretum at Flagstaff made three separate collections of Hedeoma diffusa (Flagstaff false pennyroyal) from Coconino National Forest. Sheila made two large collections, consisting of over 50 maternal lines and 2000 seeds, and one smaller collect from just 5 maternal plants yielding 113 seeds. Although Hedeoma diffusa has G3 S3 status, concerns regarding Flagstaff’s expanding development into its habitat has locally promoted this species in priority

Center for Plant Conservation
  • 08/18/2021
  • Orthodox Seed Banking

In 2021, CPC contracted the Arboretum at Flagstaff to recollect seed from a population currently held in long term orthodox seed storage as part of an IMLS-funded seed longevity experiment. The National Laboratory for Genetic Resources Preservation will evaluate how germination tested viability and RNA Integrity of seed lots decline over time in storage.

  • 09/15/2020
  • Demographic Research

Phillips et al. (1993) found that cool burns may lead to favorable increases in recruitment, however by 2001, sites with burns had significant invasion by the exotic plant, Dalmatian toadflax. (Phillips and Crisp 2000)

  • 09/15/2020
  • Living Collection

The species has been particularly difficult to keep alive in containers. It is extremely finicky about water needs. The best success so far at the Arboretum at Flagstaff was with overwintering with plants in their gardens.

  • 09/15/2020
  • Propagation Research

Further work on successful propagation and cultivation techniques is necessary. The species has been particularly difficult to keep alive in containers. It is extremely finicky about water needs. The best success so far at the Arboretum at Flagstaff was with overwintering with plants in their gardens.

Nature Serve Biotics
  • 05/02/2017

Recently has been reported from more than 100 sites in northern Arizona with a total of more than 10,000 individ- uals.

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

Threats include: exotic weeds grazing

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

60 locations in the vicinity of Flagstaff Arizona northern Arizona and locations along the rims overlooking Oak Creek Canyon.

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

Phillips et al. (1993) found that cool burns may lead to favorable increases in recruitment, however by 2001, sites with burns had significant invasion by the exotic plant, Dalmatian toadflax. (Phillips and Crisp 2000)

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

Populations overlooking Oak Creek Canyon are fairly inaccessible and are protected in the Red Rock-Secret Mountain Wilderness Area. Some of the populations near Flagstaff are threatened by development, but it is still considered to be a Forest Service Sensitive species, therefore activities on federal lands are likely to avoid major impacts on the populations.

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

More research is needed on the impact of burns and potential interactions with exotic Dalmatian toadflax. Protect limestone outcrops where the species is found Continue to survey for additional sites Investigate the basic biology and ecology of the species (incl. Substrate analysis, maximal canopy coverage, associates, and growth habitat trends).

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

Further work on successful propagation and cultivation techniques is necessary. The species has been particularly difficult to keep alive in containers. It is extremely finicky about water needs. The best success so far at the Arboretum at Flagstaff was with overwintering with plants in their gardens.

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Photos
Nomenclature
Taxon Hedeoma diffusa
Authority Greene
Family Lamiaceae
CPC Number 2153
ITIS 502889
USDA HEDI
Common Names Flagstaff pennyroyal
Associated Scientific Names Hedeoma diffusum | Hedeoma diffusa
Distribution In Arizona, this species is found on the San Francisco Plateau of the Colorado Plateau Province as well as near Flagstaff and southward in Coconino and Yavapai counties. (Arizona Game and Fish Depart
State Rank
State State Rank
Arizona S3
Habitat

Hedeoma diffusum grows on outcrops of dolomitic upper Kaibab limestone at elevations of 6640-7500 feet (2024-2287 m). The plant prefers open spots with weathered limestone solution pockets filled with 4-6 inches of soil, but also grows in vertical cracks and around the edges of boulders. (Arizona Fish and Game Department 1999)Over 40 species are found in association with Flagstaff pennyroyal. They include: ponderosa pine, gambel oak, Hedeotis pygmaea, Geranium caespitosum, and Festuca arizonica.

Ecological Relationships

As is true of all species in the genus Hedeoma, H. diffusum is sensitive to competition. Seed production is usually good, and seed life has been shown to be at least 5 years. Seed dispersal occurs primarily by wind and water.(Arizona Fish and Game Department 1999)

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

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