CPC Plant Profile: Roundleaf Four-o'clock
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Plant Profile

Roundleaf Four-o'clock (Mirabilis rotundifolia)

Seedlings of Oxybaphus rotundifolius that were germinated in late January of 2002 Photo Credit: Michelle DePrenger-Levin
  • Global Rank: G2 - Imperiled
  • Legal Status: N/A
  • Family: Nyctaginaceae
  • State: CO
  • Nature Serve ID: 160996
  • Date Inducted in National Collection: 02/10/1987

The Arkansas River Valley of Colorado supports many unusual flora. Although some taxa are abundant several are narrowly restricted to the area of carbonate shales of the Niobrara Formation (Von Bargen 1997). Oxybaphus rotundifolius is one of the narrow endemics whose distribution is limited to this area. The brilliant purple, trumpet-like flowers appear in June, opening in the morning and usually closing by mid-day.

Participating Institutions
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  • 09/19/2020
  • Propagation Research

Denver Botanic Gardens has performed germination tests and currently grows the species in the Endangered species garden

  • 09/19/2020
  • Living Collection

Denver Botanic Gardens has performed germination tests and currently grows the species in the Endangered species garden

Nature Serve Biotics
  • 05/02/2017

Known only from southcentral Colorado, the species is restricted to a narrowly distributed geological substrate. Although there are 38 documented occurrences only 23 are of good viability, and the total known population size is small. Residential expansion and mining for cement production have destroyed some plants in the past and continue to threaten the species.

Thomas Grant
  • 01/01/2010

Residential expansion and Development Mining development (limestone for cement)

Thomas Grant
  • 01/01/2010

Few known populations.

Thomas Grant
  • 01/01/2010

Kelso's (1995) research on soil fractionation of different elements such as Ca, Mg, and K may explain the distribution of O. rotundifolius. Denver Botanic Gardens has performed germination tests and currently grows the species in the Endangered species garden. Additionally, Denver Botanic Gardens has monitored populations on lands owned by the Portland Cement Company since 1995.

Thomas Grant
  • 01/01/2010

Population monitoring by the Denver Botanic Gardens.

Thomas Grant
  • 01/01/2010

A management plan needs to be designed and implemented. Research needs include understanding soil processes that may affect O. rotundifolius population dynamics. Aspects of this species reproductive biology and ecology would also be useful for conservation efforts.

Thomas Grant
  • 01/01/2010

Seed collection and banking.


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Taxon Mirabilis rotundifolia
Authority (Greene) Standl.
Family Nyctaginaceae
CPC Number 2870
ITIS 19663
Common Names round-leaf four-o'clock | roundleaf four o'clock | roundleaf four-o'clock
Associated Scientific Names Mirabilis rotundifolia | Allionia rotundifolia | Oxybaphus rotundifolius
Distribution Colorado endemic. Fremont and Pueblo Cos., in the Arkansas River Valley between Pueblo and Canon City (Kelso et al. 1995).
State Rank
State State Rank
Colorado S2

Restricted to barren shale outcrops of the Smoky Hill Member of the Niobrara Formation in sparse shrublands or woodlands. Elev. 4800-5600 ft. (Spackman et al. 1997).

Ecological Relationships

Ecological relationships are largely unknown, but this species is associated with Frankenia jamesii (Von Bargen 1997).

Common Name Name in Text Association Type Source InteractionID
Bees Confirmed Pollinator Link
Flies Confirmed Pollinator Link
Lead Institution State Reintroduction Type Year of First Outplanting

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