I want to add a photo of a native plant found on Mount Rainier and ID'd by a placard as 'Rosy Spirea'. Can't find that specific match in the database. It appears the latin name is Spiraea densiflora which is also not in the database. The closest I am finding is Rose Spirea, Spiraea douglasii var. douglasii, but no photos so I can't compare. Are these plants the same as one another?

Spiraea densiflora is a synonym of .

There aren't any pictures in the database, yet, but the USDA Plants site has some.

http://plants.usda.gov/core/pr...

Do they look like that?

Kent, yes, I think that is the correct plant. My local native field guide also ID's as alpine spirea which is listed as a common name for S. splendens var. splendens. I'll upload my photo to that entry and add whatever other info I can glean from my field guide.

On an unrelated note, what does the var. mean? I assume it stands for variety, but seems it is often just a repeat of the species name. Is this something that is used more for native plants, similar to a cultivar name?

Yep, var. is just the abbreviation for variety. It's a taxonomic subdivision below the species level. It's typically used when separate populations of a given species are not distinct enough to be classified as subspecies, but they are distinct enough to be recognized.

Spiraea splendens has two varieties for example, the "typical" variety, Spiraea splendens var. splendens and another variety called Spiraea splendens var. rosea. I assume there's something noticeably different in appearance between those two varieties, but I don't know enough about them to tell you what it might be. Spiraea splendens var. rosea has a very limited distribution in Idaho, so I'd imagine there's an isolated population on some mountain there that has different colored flowers, or growth habit, or something like that.