Rhododendron ponticum in the US?

My intern recently mentioned that there appear to be a lot of observations of a non-native rhododendron on iNaturalist, and she was right! There are more than 1,100 observations of R. ponticum in the eastern US. I can’t find any mention of this species naturalizing in the US (not included in EDDMapS, Weakley, or BONAP). Does anyone know of instances where R. ponricum is truly naturalizing in the US, or is this more likely a massive case of mistaken identify, for the most part? The common name “common rhododendron” probably isn’t helping, and if the computer vision system thinks this species is in the US then it is probably contributing to the problem. I’m guessing pretty much all of these that aren’t cultivated actually show a native species (R. maximum being the most likely). Thoughts? Perhaps these are widely planted and often observed in gardens?


This is a very popular small-size species in gardening; often runs away from gardens because it can withstand frosts up to - 24 degrees Celsius; of course it may be misidentified, but if it is in the gardens it will also be in the area …

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A lot of them are probably correct identifications of cultivated plants. But it could also be an example of “runaway” misidentification where people chose the top auto-ID suggested species and others confirmed it using the auto-ID, which triggered the “seen nearby” aspect of the auto-ID and causing other nearby users to choose that species. This has been mitigated with recent changes to how computer vision suggestions are given, but it used to be a huge problem.


Before doing any Rhododendron id’s in the Eastern US, based on past experience I recommend taking a quick (or long, depending on season) pass through them in Identify and click “x” on the many obvious cultivated obs that will be in the mix. (You can always correct those cultivar id’s later, but it sorts them out for later.)


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