While any tree is better then no tree, you will have some that will last longer then others, all of them will last longer if submerged permanently and not, like some others stated, spend a portion of the time above water and the rest of the time below, they rot fast that way.
My biggest concern from your post was the depth that you are talking about placing this cover. Im a long ways from a professional on the subject, but do some research on this forum, I dont think you will be providing any cover for baitfish at 12 to 14 ft of depth, probably not even much at the tops of those trees if they are anything below 6 ft of depth.
Like I said, I'm no pro at it other then spending a good bit of time fishing over the yrs, but some of the guys on this forum might be able to give better advice, they may tell me im crazy and thats the perfect depth for your cover. Good Luck!
