I hadn't heard of either tree. Wrote in the solution and forgot to research on Google.
Aside from that hitch with 18, I found this fun but the easiest Prize in a long while. Filled in the grid so fast that I didn't keep my customary COD long list.
FOI 1d, LOI 10 (aside from 18 parsing).
Obvious theme, but some of the thematics were tricky. Thanks to Brendan.
COD 10, runner-up 26...those were the only ones I made notes of.