BC Conservation Data Centre: Conservation Status Report
Rhododendron macrophyllum
Pacific rhododendron
| Scientific Name: | Rhododendron macrophyllum |
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| English Name: | Pacific rhododendron |
| Provincial Status Summary | |
| Status: | S4 |
| Date Status Assigned: | April 30, 2019 |
| Date Last Reviewed: | April 30, 2019 |
| Reasons: | This species is fairly abundant in a limited range in BC. Threats are not considered significant. |
| Range | |
| Range Extent: | E = 5,000-20,000 square km |
| Range Extent Comments: | Rhododendron macrophyllum occurs in a few specific areas in southern British Columbia (Rhododendron Lake and Shawnigan Lake on Vancouver Island, Mount Elphinstone on the Sunshine coast, and Hope-Princeton Highway and Skagit valley). The range is ca. 13,000 km sq. |
| Area of Occupancy (km2): | EF = 26-500 |
| Area of Occupancy Comments: | [D] At least 16 2 km x 2km grid cells are occupied in the Skagit Valley, but many others are likely occupied. |
| Occurrences & Population | |
| Number of Occurrences: | BC = 6 - 80 |
| Comments: | There are substantial numbers of localized populations (Desrosiers and Douglas 1996; COSEWIC 2014). |
| Number of Occurrences with Good Viability / Ecological Integrity: | C = 4 - 12 |
| Comments: | The majority of (60%) of populations in the Skagit Valley showed good to very good vigour (Desrosiers and Douglas 1996). |
| Number of Occurrences Appropriately Protected & Managed: | C = 4 - 12 |
| Comments: | Many of the occurrences are in protected areas (Desrosiers and Douglas 1996; COSEWIC 2014). |
| Population Size: | EF = 2,500 - 100,000 individuals |
| Comments: | This species is abundant in the Skagit Valley. It reproduces asexually via layering producing canes and less often by sexual reproduction. A very conservative estimate of the # of canes in Desrosiers and Douglas (1996) is between 9550-29,600 in the Skagit Valley alone. Many subpopulations were not counted and one of the subpopulations was over 20 hectares and completely covered in Rhododendron macrophyllum. The average "population" counted was 57 canes, and the average # of inflorescences was 62 or at least ca. 1 inflorescence per cane. Thus, reproducing individuals could be interpretted as being up to 30,000+, however, most of the reproduction is occuring via layering. In addition, 400 plants were reported from Rhododendron Lake on Vancouver Island. |
| Threats (to population, occurrences, or area affected) | |
| Degree of Threat: | Slightly threatened |
| Comments: | [D] Climate change is a potential threat for Rhododendron macrophyllum. A dry and warming climate may not heavily impact the populations, although increased growing degree days and progressive succession may lead to the expansion of forests, resulting in out-shading. The restricted range of this plant may limit its capacity for adaptation through migration (BC Parks unpublished). Recreational pressure may also be a threat, but neither this nor climate change are considered significant threats. |
| Trend (in population, range, area occupied, and/or condition of occurrences) | |
| Short-Term Trend: | U = Unknown |
| Long-Term Trend: | U = Unknown |
| Other Factors | |
| Intrinsic Vulnerability: | Rank Factor not assessed |
| Environmental Specificity: | D=Broad. Generalist or community with all key requirements common. |
| Comments: | Rhododendron macrophyllum requires a habitat that is regularly disturbed and is characterized by well-drained soils. |
| Other Rank Considerations: | |
| Information Gaps | |
| Research Needs: | |
| Inventory Needs: | |
| Stewardship | |
| Protection: | |
| Management: | |
| Version | |
| Author: | Penny, J.L. |
| Date: | February 27, 2014 |
| References | |
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BC Parks. 2014. Skagit River Rhododendrons ER #106. Report prepared for Ministry of Environment BC Parks, Victoria, BC.
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Desrosiers, J. and G.W. Douglas. 1996. Status Report on Pacific Rhododendron, Rhododendron macrophyllum, in Canada. Unpubl. Rep. submitted to the Comm. on the Status of Endangered Wildl. in Canada. Ottawa. 24 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. 2014. Conservation Status Report: Rhododendron macrophyllum. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Dec 23, 2025).