Hello, and welcome to my first guide. It probably wont be good, and honestly im not even going to try to make it amazing. Im simply putting up my build because the one riot made is completely fail. Why play a champ like a schmuck? All the riot maokai could do was slow people and negate a little damage.
With my version you can literally carry a terribad team on your big bark, i mean back..
So, given that I have only played abotu 10 games with maokai so far my observations are that his abilities can be put to a lot better use than just off tanking.

For runes, I've decided to add a lot of surviveability. Because we are a melee champion we will still be taking some beats regardless.
I decided to go with magic pen marks, armor seals, magic resist glyphs and flat health quints.
A not so bad idea is to ditch your armor seals and get mp5 but its up to you. I havent found the need to be constantly popping blue pill, its just a matter of being smart with your casts.
Yes you can harass the **** out of the opposing team with your sapling but really that just leads to you tower hugging cuz you went oom and dont want to lose xp.
so, once again. playing smart and combo'ing your moves is a lot better than harassing and missing.

For masteries I went with your basic caster approach. I've played him as 9-0-21 and 9-21-0 and It seems that he benefits much more from the move speed cdr and extra experience than just having a lil more staying power. 1 thing to really remember is that this tree is the slowest champion in the game. With boots of swiftness you only get 395 move speed. which is really really low.

Heres where I'm sure the debate will begin. However, because its my guide, who cares right?
I start out with a dorans ring. With our passive we dont need the health regen and I have never been forced out of a lane. I always solo top or mid and never have an issue.
The added mp5 and health from the ring are a nice bonus. Our ap doesnt scale particularly well so instead of ignoring it we just get more ! YAY.
Second i like to get a tears to help with the early mana starvation. The reason i ignore boots for a while is because with our w and q we can catch or run and slow the enemy and not generally have to worry about being caught or left in the dust.
Next up I will either buy a blasting wand or get cdr boots. This is all dependant on how the game is progressing for you. My experience is that if you are not getting any kills you need more ap to hurt them a lil faster. If im doing fine and gettign kills i will buy the boots so i can move around the map and help gank.
Next up I will complete the archangels jsut because i dony like things left unfinished and immediately start building into Roa. I generally ignore the catalyst and get the rod first to continue the pain. Some people will say that by now its too late to get a RoA. It only takes RoA 10 minutes to fully power up. I will generally have the archangels and RoA finished at the 30 minute mark with 5ish kills. From there i like to get soem more survivability and also piss off the other team. I will build into an abyssal for the ap, mr and of course its passive which is amazing considering you are generally the center of the fight. Last and not least i like to get a zhonyas for the armor mostly but the 100 ap is nice too. Dieying too fast? pop its active and watch the other team scramble to find a new target. Other optional items that I find work nicely on maokai are:
Rylais
Sheen/ Lich bane ( move faster? why not, more ap yessir, wait so i get to nuke them and then get up from the ground and smack them for 500 more damage? AWESOME.
Merc treads.. Heavy cc on the other team? might want to switch to these!
Frozen heart. Melee heavy other team? it helps with the cdr and lots of mana which we obviously love to go along with our archangels.

Ill keep it short, I max sapling toss first. Towers dont target them so you can get in those last shots from a huge range.. Wait **** did you miss? its ok.. cuz it will chase them down now mwahahahahahha.
Second i max out w. Has the best ap scaling of all of our moves and roots them in place. love it!
Last i max our q, why? **** damage output, yea nice slow.. but if you do no damage why are you slowing them anyways?
Obvisouly we put points in for our ult which to me is just meh, Noone really rights in it. People are a little smarter than that. Also it does almost no damage. the 20% damage reduction is amazing.. If you can get the other team to sit there and not leave it though..

So, all in all we have a great champion. Im just getting started and I feel he will be nerfed soon. Huge range on the e (sapling toss) and the damage they do is rather impressive at low levels too.
So lets talk about how you should initiate.
I read a lot of guides myself and they never seem to tell you what to cast and when.
Lucky for me its going to be pretty simple.
Dependign on the situation.....
If you are laning and wantign to go in for soem big damage, get close enough to cast your w, once you rise up out of the ground toss a sapling right behind them, then use every ability you can to kill them as they come up off cooldown.
If after lvl 6 ill even drop my ult for the extra 100 damage. Make sure you proc it before they leave the circle though!!!!!
If you are coming in for a gank its a GREAT idea to throw saplings in their retreat route before you initiate. Obviously dont let them see them and try to time the creep wave so they dont pop it too early.
Gl and have fun with Maokai, I know I do!

After some more experimenting I have decided to bump rylais up on the list and put off finishing Archangels. The ap boost isnt that great right off the bat and having your saplings slow the enemy is great. not to mention when you pop your ult you can slow everyoen thats inside it is priceless. Even though on the list it comes up after abyssal and zhonyas feed free to build it immediately after the RoA. Personally I like the added surviveability given from the mr of abyssal and the armor from zhonyas but the choice will always be yours and will always be dependant on how the game is progressing. If you arent full on team fightign at this point why not build the ap first for the better harass. Enjoy and please + vote if you;ve given its a shot. I hate seeign -1 because someoen doesnt think it will work.......... If you dont think, try it and see for yourself.
Oh and for those saying that it wont work for ranked? I use it in ranked and it works just great.