The pith occupies a large portion of the stem diameter and hence the distinguishing color is easy to see at all times of the year. However, the pith of the current year’s growth cannot be relied upon; it may be light brown or “off-white” in both species. The corollas are rotate, i.e., flat with a very short tube, as in Viburnum.
1. Pith white (sometimes a little brown at the edges); mature fruit purple-black; inflorescence distinctly broader than long and ± flat-topped, blooming in early to mid-summer and fruiting in late summer to fall; lowest node of inflorescence with 4–5 (–7) rays.
1. Pith tan or orange-brown on branches 1 year or more old; mature fruit red; inflorescence about as long as broad or up to 1.5 times as long, ± pyramidal or elongate, blooming in early spring and fruiting in early to late summer (depending on latitude); lowest node of inflorescence with 3 rays (main axis and 2 branches).
All species found in Sambucus
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. June 21, 2018. https://www.michiganflora.net/genus.aspx?id=Sambucus.