Clash-of-clans – What do you get for mining the new Christmas tree

Campaign levels are like puzzles, and typically require use of specific units and/or upgraded units to succeed - especially if you are seeking a 3 star result. A few general tips for success -

• Use Tier 1 troops (barbarian, archer, goblin) in hordes to attack single target defenses (cannon, archer tower, spring traps). You'll loose a few, but the horde will overcome.
• Use Tier 2 troops (giant, wall breaker, balloon) for their
  specialized abilities, particularly to crack splash damage defenses
  like the mortar, which can wipe out your hordes. When using the
  balloon, be sure to wipe out air defense first.
• Campaign levels are not timed, so once defenses are down you can wait indefinitely to win if you want to save troops.
• Queue some troop production in your Barracks before starting a fight (even though you are full). Some of these troops will already be ready and waiting as soon as you are complete.

For per level strategies, check out the level by level video guides here.

I will also add that upgraded units help a lot. As I now attack the high-end levels, it is much easier to 3 star now that I have most units upgraded to level 4 or level 5. I also make use of the Barbarian King, which I believe makes these levels much easier since he is a very good tank, and can draw a lot of fire while your hordes disassemble the defenses.

Christmas trees are completely random spawn just like any other ground obstacle. (Only spawning when you aren't playing )

From playing on two different accounts: I noticed that my lower level account spawned 4 Christmas trees while my high level account only spawned 2 during this seasonal theme. In addition, the lower level account had much more room free to spawn which may have improved my chances for spawning them.