AP Maokai's poke is not something to be messed around with! He's got a much stronger earlier game than support Teemo and his saplings are equally effective. Throw them in bushes for better results, but since your enemies will probably just avoid bushes, feel free to throw saplings straight at them.

Early Game
Maokai's saplings (E) are so good early game. Throw them in the bushes (make sure that they won't hit the wave though) and zone out the ADC from their wave. Saplings are also super useful in the river to prevent ganks. AP Maokai's engage is VERY bad, so make sure to only initiate fights when you get a gank or at 6. Basically, poke the enemy out with saplings and let your ADC farm peacefully. Walking up to the enemies is also super effective zoning, just be careful of dying instead. You only have a little bit of sustain with your P.

ALSO, Maokai is very mana hungry early game. Be mindful of this and rush Lost Chapter!

After Laning Phase
Around when tier 1 bot tower is down and you have Liandry's, you should definitely start roaming. Throw your saplings in every bush and use them to secure objectives, much like Teemo shrooms. Remember that they do expire in ~30 seconds so make sure that your saplings don't expire before the objective is up. ALSO, YOU MAY LOOK LIKE A TANK BUT DON'T EVER WALK UP! Only W root and Q combo if you have allies around and the enemy doesn't.