The colour of the wood doesn't much look like plum to me, but it is small diameter, so it might be since the heartwood wouldn't be apparent in something that size yet. I always found it weird in NZ that the Maori never developed bows, but to make up for it, developed trench warfare and actually changed the landscape to give them the advantage in a siege. They made some pretty crazy weaponry too. When I was there I didn't know any bow making yet, but looking back on it, I would have loved to try making a Manuka bow. There is also so much invasive scotchbroom growing there now that that would certainly be a good option. I worked on an oldtimers heritage plum orchard that had fallen into neglect for some time just north or Auckland. I pruned back over a hundred old plum trees. Looking back on it, I feel like punching myself in the nuts I missed out on so much wood that just got turned into firewood. I loved NZ and regretted having to leave. Amazing place. You can try the nephrite jade you've got there for arrowheads as well. We have the same kind of jade all over here in Taiwan and I normally go collect it after a typhoon to turn into arrow heads. Can't knap it, so you need to use a wet wheel, but it makes a durable arrow head.