Perhaps that's a bug? The thorny, flowery bushes that you can chop down to get fiber seem to respawn for me, but I only figured out they give plant fiber later on (because I never bothered trying to chop them down before) so I'll have to double check that. But I'm fairly certain they respawned for me. However, some of the bushier trees that just give wood do NOT seem to respawn for me.
Also: thank you! There's still a ton of work to be put in but it's coming along nicely, very much thanks to some lovely contributors that have joined in to help! I couldn't do it without everyone's wonderful help.