The whole right side died back and only left side is alive ugh… I have another one that I cut back but I honestly am stumped with alder( no pun intended ) … it dies back .. doesn’t heal well in fact I’ve never even noticed callus building up on this soft wood .. I’ve had 3 alders so far 1 died … 2 are not great for bonsai.. maybe Alder Alnus Serrulata can’t be used for bonsai. I’d love to collect an alder again.. I have 2 I’m still playing around with but I wonder if it has to do with pruning … not letting suckers take over , deep pot , and what type of soil it’s planted in.. this tree was in pumice , lava and akadama recently.. where as when it was in that terracotta pot, it was just mostly in field soil high organic media