OK, not one to miss the chance to beat a dead horse, I just got my
copy of Jepson out of storage. Revised ed. 1993 by Hickman. It
shows that Sambucus glauca in now Sambucus mexicana. The
latter name having priority by publication date. This is the "Blue
Elderberry" found at lower elevations across the Western U.S.
White powdery covering on the berries is "glaucous" from which
the specific epithet "glauca" was derived. Sambucus melanocarpa
is much less common and grows in low clumps of three to six feet.
Sambucus racemosa is widespread and quite variable, with both
coastal and alpine varieties, and is likely the common species in
British Columbia. S. racemosa grows into large clumps but not as
large as S. mexicana, which can grow to over 15 feet in optimum
conditions. S. racemosa often produces fruit that is bright red.