It looks like a yucca. Here is a link that might be useful: yucca

Thank you for your help. You really are fast. Carol

I see you're new here, welcome. Pls. do some reading around here on mixes. While it's good that you're already using Cactus & Succulent mix (C&S for short), you will quickly see that many if not most of us here have learned to amend our C&S mixes (w/perlite or pumice, at least 30% or 50% to be safest), 'cause these days, commercial mixes have too much peat in them (kills out plants) &/or include wetting agents to retain water (also kills our plants). Others of us on here use mixes you'll see mentioned as Gritty Mix or variations of 5:1:1, things like that, which over time folks have learned worked well for them. Also some of these pre-made mixes contain fertilizer as well, which many of us wish to control ourselves rather than someone unfamiliar w/ our growing conditions. There are lots of opinions on mixes, but key & accepted by all of us is that to grow C&S, we need fast draining mix & what you've pictured above doesn't look like that. So that's an improvement that could be made easily & help the plants more that almost anything else one could try.

Regarding the elder it looks just like those in a Seattle park planting that is supposed to be all local natives. Friend and I guessed they were received as blue elderberry (Sambucus mexicana, syn. S. cerulea) but are obviously not that species, having a different structure and being in leaf and flower in December! A related species from Mexico?