Article:
Creating a LARP Group: Props
The biggest thing that separates a live-action game from a table-top game is the immersion players get from the use of props. The whole point of playing LARPs is that you are your character - you eat what your character eats, you sleep where your character sleeps, and you do what your character does. This is the atmosphere you want to support.
So obviously, the big question is how you should handle props to support this immersion?
There are two types of immersion that happen in LARP games.
The first immersion type is used to make people accept the fact that they are their character. This is not too difficult, as someone putting on a costume can easily assume the role of their character. Once a newer player gets the fact that they are their character, they'll be hooked. The way you support the first immersion is by having a large amount of kit on hand that new players can borrow (or possibly purchase afterward), so they actually get in costume! I have seen the difference between a new character who is given costuming to use as opposed to a new character who brings their own, poorly-made and less immersive garb. While the former easily identifies himself as a character and finds it easier to meet with other characters, the latter ends up playing a character that is essentially no different than the player in real life.
So remember to set aside some garb and weapons in order to accomidate the newer players. Have it be at least decent quality and let them pick what they want. If they had a fun time and want to play the game more, offer to sell it to them at cost! This will not only give them a buy-in to keep playing, but it will make them think "the guys running this game really do care about the players!"
The second kind of immersion happens when you go further than player expect you to go with props. The brain identifies patterns and automatically expands further on them. By performing actions that players have not thought of yet, existing players will be shocked, scared, or amazed. Since they hadn't though of that possibility, they start analyzing how their character would react, forcing them IG.

For the bark, you can either buy fake bark (pretty expensive), use real bark that you treat with something like minwax polyurethane spray, or some sort of tree bark pattern. My gut tells me that the real bark would give the best results, but it might take a couple of iterations.