BC Conservation Data Centre: Conservation Status Report
Phlox speciosa
showy phlox
| Scientific Name: | Phlox speciosa |
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| Scientific Name Synonyms: |
Phlox speciosa ssp. occidentalis
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| English Name: | showy phlox |
| Provincial Status Summary | |
| Status: | S2 |
| Date Status Assigned: | September 30, 2008 |
| Date Last Reviewed: | May 06, 2022 |
| Reasons: | Phlox speciosa is only known from a very small area in BC, from fewer than 10 locations. The species occurs within a region that is subject to ongoing habitat loss and degradation due to private property development, agricultural practices, and the spread of invasive plants. |
| Range | |
| Range Extent: | A = <100 square km |
| Range Extent Comments: | Based on recent field surveys, the known extent of occurrence of Phlox speciosa in B.C. is 57 square kilometres. Phlox speciosa occurs in the southern Okanagan Valley, northeast of Keremeos, in a small area around Yellow Lake, Twin Lakes, and White Lake (COSEWIC 2004m). |
| Area of Occupancy (km2): | AD = 1-25 |
| Area of Occupancy Comments: | Based on crude field estimates, the area of occupancy for Phlox speciosa in B.C. was estimated at 0.9-1.4 square kilometres (COSEWIC 2004m). The discovery of a new subpopulation near Horn Lake in 2007 (T. McIntosh, pers. comm.) may have increased this area slightly. The species is more densely distributed in the centre of its range than towards the edges of its range. Using a 2 km x 2 km grid, the species occupies 19 grid squares. |
| Occurrences & Population | |
| Number of Occurrences: | A = 1 - 5 |
| Comments: | There are five element occurrences of Phlox speciosa in BC, several of which consist of multiple subpopulations. Nine populations were formerly recognized (COSEWIC 2004m), but these populations are now lumped together as occurrences (for practical purposes) which, under the NatureServe (2004) "Habitat-based Plant Element Occurrence Delimitation Guidance" criteria, have separation distances of 1-3 km and are separated by apparently suitable habitat and/or dynamic landscape mosaics. Information about P. speciosa's dispersal capabilities would be helpful in defining element occurrences further, but little is currently known about the species' dispersal in B.C. or elsewhere. |
| Number of Occurrences with Good Viability / Ecological Integrity: | B = 1 - 3 |
| Comments: | Two (40%) of the element occurrences of Phlox speciosa in B.C. are assumed to have good viability. These include COSEWIC's White Lake, Twin Lakes, Park Rill and Yellow Lake West, South and East populations. Population viability assumptions are based on population size, condition and landscape context (COSEWIC 2004m). Estimates for other variables that influence population viability are not available. |
| Number of Occurrences Appropriately Protected & Managed: | B = 1 - 3 |
| Comments: | Most of the area of occupancy occurs on private land that is not being managed to protect rare plant species. The populations that occur on provincial Crown land do not occur in protected areas and do not have any formal protection or management. A portion of the White Lake population occurs on federal National Research Council Land within the White Lake Biodiversity Ranch. The ranch is managed by the Nature Trust in conjunction with the South Okanagan Similkameen Conservation Program. The portion of the population that occurs on the ranch is likely appropriately protected and managed. |
| Population Size: | FG = 10,000 - 1,000,000 individuals |
| Comments: | The population size of Phlox speciosa in B.C. was estimated at 25,000- 220,000 individuals, based on very crude population size estimates completed during field sampling in 2003 for the COSEWIC status report (COSEWIC 2004m). Based on the discovery of an additional large subpopulation in 2008, estimated to consist of 10,000 to 100,000 plants (T. McIntosh, pers. comm. 2008) this estimate can be raised to 35,000 - 320,000 individuals. |
| Threats (to population, occurrences, or area affected) | |
| Degree of Threat: | Moderate and imminent threat |
| Comments: | The scope, severity, and immediacy ranks are based on the primary threat to Phlox speciosa in British Columbia, which is the threat of habitat loss and degradation due to recreational property development. The scope of this threat is inferred to be moderate based on the proportion of the area of occupancy that occurs on private land (ca. 34%; O. Dyer, pers. comm. 2008). The severity of the threat is suspected to be high because development activities such as the building of driveways, recreational homes, and outbuildings are likely to destroy the species' habitat with the effects being essentially irreversible or requiring long-term recovery (> 100 years). This threat has resulted in habitat loss in the past, based on observations of the species growing within metres of houses and driveways on properties that presumably occupy former P. speciosa habitat. This rating is somewhat moderated by the likelihood that severe impacts will apply to only a small proportion of the current area of occupancy, and losses are expected to be small in area, and cumulative. The immediacy of the threat is suspected to be moderate since properties within the extent of occurrence have recently been for sale and will likely be developed. Similarly, properties that coincide with portions of the current area of occupancy are likely to be sold and developed in the near future. Populations and habitats are also at risk due to a number of real and potential secondary threats: habitat degradation due to livestock grazing and proliferation of invasive species, habitat loss and degradation due to fire suppression, habitat and population loss due to direct and indirect effects of global climate change, and population loss due to weed control activities (COSEWIC 2004m; T. McIntosh, pers. comm. 2007; Penny 2007). |
| Trend (in population, range, area occupied, and/or condition of occurrences) | |
| Short-Term Trend: | U = Unknown |
| Comments: | The short-term trend in population size, extent of occurrence, area of occupancy, number of occurrences, and viability/ecological integrity of occurrences is unknown due to a lack of baseline data and monitoring. Habitat losses are occurring within the extent of occurrence, however, due to increasing levels of property development for recreational and agricultural uses (COSEWIC 2004m). |
| Long-Term Trend: | DE = Decline of 30-70% |
| Comments: | The long-term trend in population size, range, area of occupancy, or number or condition of occurrences is unknown due to a lack of baseline data and monitoring. Two or three historical populations have likely been extirpated (COSEWIC 2004m). Lea's (2008) habitat mapping showed losses since European settlement of 50% for gently-sloping Ponderosa pine - bluebunch wheatgrass communities, 33% for Douglas-fir - pinegrass communities, and 61% for overall gentle slope grassland and shrub-steppe communities in the Okanagan and Similkameen drainages. |
| Other Factors | |
| Intrinsic Vulnerability: | U=Unknown |
| Comments: | The species' frequency of reproduction, as measured by the proportion of flowering plants, can be high (6-73 percent [K. Barton, unpubl. data]). The species' age of maturity, fecundity, and dispersal capability are unknown. |
| Environmental Specificity: | C=Moderate. Generalist or community with some key requirements scarce. |
| Comments: | Within its small range in B.C., Phlox speciosa grows in a wide variety of habitats, but its distribution is limited by its apparent requirement for a specific elevational range (680-1120 m), open habitat (< 25 percent canopy closure), on level sites or slopes with cool aspects and sites that have a lower slope macroslope position (COSEWIC 2004m). |
| Other Rank Considerations: | N/A |
| Information Gaps | |
| Research Needs: | Research is needed to determine the dispersal capabilities of Phlox speciosa and the degree to which gene flow occurs between B.C. and U.S. populations. |
| Inventory Needs: | All extant populations of Phlox speciosa should be identified by ground surveying areas of potential habitat (mapped using biogeoclimatic mapping, digital elevation modelling, topographic mapping, and broad ecosystem inventory). Additionally, reliable population size estimates of all extant populations need to be established, and demographic information for extant populations should be collected. |
| Stewardship | |
| Protection: | All element occurrences of Phlox speciosa in B.C. should be protected. |
| Management: | Management needs for Phlox speciosa include avoiding the development of facilities, buildings, roads and trails (including hiking, cycling, and horseback riding trails) and prohibiting recreational off-road vehicle use in areas of suitable habitat. Measures should be taken to ensure that road maintenance practices do not damage or kill plants or cause the spread of invasive species. Herbicides should be used with caution when necessary to control the spread of invasive species. Tree harvesting should be avoided except where treatments are aimed at maintaining or improving stand characteristics for Phlox. Seeding with non-native species should be avoided, and harvesting or seed collection of native plant species should be prohibited. Also, current range condition should be maintained, range use plans must be adhered to by licensees, and erosion control measures should be avoided. |
| Version | |
| Author: | Barton, K., J. Penny and S. Hartwell |
| Date: | July 10, 2008 |
| References | |
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COSEWIC. 2004m. COSEWIC assessment and status report on the Showy Phlox Phlox speciosa in Canada. Comm. on the Status of Endangered Wildl. in Can. Ottawa. vi + 24pp.
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Environment and Climate Change Canada. 2017b. Recovery Strategy for the Showy Phlox (Phlox speciosa ssp. occidentalis) in Canada. Species at Risk Act Recovery Strategy Series. Environment and Climate Change Canada, Ottawa. 2 parts, 16 pp. + 18 pp.
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Lea, T. 2008. Historical (pre-settlement) ecosystems of the Okanagan Valley and Lower Similkameen Valley of British Columbia - pre-European contact to the present. Davidsonia 19(1): 3-36.
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McIntosh, T. 2007. Report on 2006 NRC White Lake species at risk surveys. Report prepared for the Herzberg Institute of Astrophysics, Dominion Radio Astrophysical Observatory, National Research Council of Canada, 24 pp.
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NatureServe. 2004b. Habitat-based plant element occurrence delimitation guidance, 1 October 2004. Available: http://www.natureserve.org/explorer/decision_tree.htm (accessed Mar. 17, 2005).
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Penny, J. L. 2007. Best management practices for rare/at-risk plants in rangelands. Conserv. Data Centre, Ecosys. Branch, B.C. Minist. Env. Victoria, BC. 12 pp.
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Please visit the website Conservation Status Ranks for information on how the CDC determines conservation status ranks. For global conservation status reports and ranks, please visit the NatureServe website http://www.natureserve.org/.
Suggested Citation:
B.C. Conservation Data Centre. 2008. Conservation Status Report: Phlox speciosa. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 7, 2026).