-About me: I am a Maokai Support (near)OTP who plays under the alias - FunnyBunnyH#EUW . I picked up the game in S10 and over these few years I accumulated a few 1000s SoloQ games on the Mighty Tree as a support, while climbing to Diamond/Master rank.

-The reason for this guide:
When I was browsing for support specific Maokai guides, I couldn't really find a really in-depth guide that is also up-to-date.

-Why Maokai support:
Maokai in my opinion is probably the best all-rounder tank support in the game. He has a ton of CC, great both as an engage- or peel support, amazing at establishing vision thanks to his saplings, and his kit is overall very well suited for objective centered metas (the ones we have in recent years).

-Pros:

Strong CC/utility (suitable for any comp)

Good Vision Control

Easy to execute kit (beginner friendly)

Strong Scaling (dmg and survivability)

Is a flex-pick (less counterpicking)

Good synergy with almost any lane partner

Not many hard matchups/counterpicks

Not often picked/banned

-Cons:

weak lvl 1(certain 2v2 matchups can be difficult early game)

low influence in games where your team is behind
(if your team lacks damage, your engages don't really work)

Requires a stronger matchup knowledge than traditional Tank supports
(Maokai's early sustain is weak and he doesn't have dmg mitigation in his kit so you need to be more thoughtful of your engages in lane)

Resolve is the most commonly used primary rune-tree when building tank, and for a good reason.

Maokai unlike traditional tank supports, doesn't have any damage mitigation in his kit, so he heavily relies on the extra resistances Aftershock provides, especially when engaging against multiple opponents. You also have good "sticking power" with your kit, so you can reliably land the damage part of the keystone as well.

From the 2nd row neither rune is really amazing, but overall Font of Life is the most reliable choice. Demolish is an okay rune if you have a favourable bot 2v2 matchup, but you can't really know for sure if you get the chance to proc it in lane, and it's value is somewhat limited once the plates are gone.

3rd row all options are decent, Bone Plating is useful at every phase of the game, but if you have a lane where you are not really under a threat of dying, you might wanna opt for Conditioning. With damage creeping up again in recent seasons, I personally started to default to Conditioning more for better survivabilty in teamfights. Vs aggro ADC picks ( Draven, Samira, Kalista) Bone Plating might still be required. Second Wind is usually picked vs double poke, but your passive and the two pots should be enough sustain early if you are not eating every skillshot/letting your opponents constantly aa you, so only take it vs the most oppressive poke lanes (long range ADC+range support).

From last row generally pick Unflinching. With the buffs to this rune in S15.9, it always gives 10+10 AR and MR now, which is just very valuable in most games, especially early-to mid phase.
There are games where enemy is rather low on CC and you are not the primary CC target, so Overgrowth is viable (it scales better). If you playing into a hook/engage support though, you want Unflinching, or even vs something like Karma+Jinx where the slows will give you the resistances often.
Revitalize is an okay choice as it helps with your FoL healing and potential Shielding with Locket of the Iron Solari, it also affects your passive healing, but rarely taken.

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2ndary runes are more flexible, and usually come down to playstyle/preferrances. In this part I will explain what your options are and what the benefits of each are.

- Inspiration: With the nerf to Biscuit Delivery (doesn't provide mana anymore), this 2ndary tree became slightly less appealing on 14.19. Hextech Flashtraption and Cosmic Insight still offer reasonably good value, so if you don't mind the lack of mana, it's still a decent choice.

- Sorcery: With MS systems getting nerfed in 14.19 and the initial MS nerf to Maokai in S14, this rune tree became even more appealing IMO.

Celerity for extra movement speed, this rune helps to offset the initial base MS nerf to Maokai, and the %MS scales really well with Boots of Swiftness or any of the Winged Moonplate items.
Opting for Celerity also makes you less bound to MS oriented items (less trade-off for buying Armor/MR boots or rushing Locket instead of Trailblazer 1st item...etc), so in a sense it offers a bit more flexibility with your builds.

Nimbus Cloak is one of the strongest minor runes in the game IMO. This rune offers superior engage/disengage when you use Flash. There are a ton of situations where this rune saved my life when I got jumped on, and it also helps a lot with catching up to people, be it one you want to kill or a teammate you want to save.
It also activates on Ignite (/ Exhaust), and since Ignite has a higher range than our W, it's something that can be a difference maker between being able to catch someone or them getting away.

-Honorable mention - Domination: As far as I seen, this rune-tree is mainly picked for Relentless Hunter, but in my opinion Celerity is just a better MS rune. Relentless Hunter is only active out of combat, and you also need to stack it up, while Celerity is active from the start of the game.

The other rune options in this tree aren't that valuable either compared to what Inspiration/Sorcery has to offer.

By default you should pick Flash and Ignite.

One great thing about Maokai support is that he offers insane kill-pressure in lane once he unlocks both his Q + W, and Ignite dmg is usually a difference maker between being able to burst down an enemy or not. It also helps vs any healing they might have with an utility support or Heal summoner.

Exhaust is generally taken with teamfights/later stages in mind, when you have a specific assassin/dmg threat you want to shut down, or when Ignite doesn't provide much value outside of lane (generally vs tankier comps).

Since Maokai generally doesn't have very one sided 2v2 bot matchups (and even in those you can "fish" for openings), you generally want to keep your chances of securing early kills in lane, this is why Ignite is taken as the preferred summoner.

-Starting item:
With 14.1 rolling out, World Atlas became the only choice for starting item. Once completed, you have 3 options that synergize well with Maokai:
- Solstice Sleigh
- Celestial Opposition
- Bloodsong

Solstice Sleigh: Overall the most "universally good" option out of the 3 as it will always provide value. It's useful both in a peel oriented build (ms+heal for the carry you are trying to proctect) and in an engage oritented one (ms to help allies catch up to you).

Celestial Opposition: Bit situational, but does an excellent job at mitigating front loaded burst. The 2 seconds slow on it is also very valuable, helps with escaping after getting caught or ensures that you can catch up to opponents after your initial engage even if they flash away. The main drawback of the item is that it does somewhat poorly vs poke (easy to proc it). Generally build it with engage oriented builds or vs "pick comps".

Bloodsong: Also situational, but pretty underrated. It's good in games where opponents have a lot of sustain, as it helps bursting down enemies you manage to catch out. I generally build it vs utility supports, or when the opposing team has a lot of champs with in-built healing in their kit.
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-Boots:
Boots of Swiftness is the most commonly built/optimal choice.
One reason is it's price, compared to the defensive options it costs 200/300g less, which might not look like a lot, but on support budget every gold counts.

Another reason is that while Maokai has great target lockdown and sticking power with his kit, he can struggle to get the initial engage going, because his W is rather short range. The extra MS helps a lot in this regard.

Defensive options like Mercury's Treads or Plated Steelcaps are taken only in very specific situations (Ton of CC on enemy's side,(multiple) high AA-based dmg threats), and even in those cases you want to consider if the extra defense/tenacity is worth sacrificing your mobility.

-Our 1st item will be determined by our main role in teamfights.

Locket of the Iron Solari: If you have an ADC you really need to protect (something like a Jinx/ Kog'Maw/ Aphelios (but could be an important carry in other roles as well), or if the enemy team is very dive heavy, you generally want to rush this item.
The AoE shield it provides helps to keep your teammates alive and you generally don't mind the lack of MS on the item because in these games the opponents will look to jump on you and your teammates anyway (opposed to you trying to jump on them).

Trailblazer: If you have a more utility based carry ( Jhin/ Miss Fortune/ Ziggs...etc) that doesn't rely on peel that much or you have other champions in your comp that can help keeping your backline alive, you want to build this item, as it helps to engage onto enemies easier thanks to the MS it provides.

If you happen to snowball in the early game you can opt for Dead Man's Plate instead for an extra 500g (it provides an extra 100HP and 15AR and also offers a bit of extra burst at your initial engage).

Note: Trailblazer and Locket of the Iron Solari are not exclusive, you can build them together (usually with Trailbazer 1st item, if you are just looking for a cheap all around good defensive item as your 2nd).
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-Our 2nd/3rd item will mainly depend on what we need the most (anti-heal, more AR or MR, more peel...etc).

Thornmail: Very strong AR item vs AA reliant champions. It only costs 2450g for 150HP and 75AR. With a slightly awkward build path it doesn't feel as good to rush as a 1st item anymore (only has a single Ruby Crystal worth of HP which makes you rather squishy), but it's a very good 2ndary AR item for it's cheap price, especially if you need the anti-heal part of it.

Randuin's Omen: Pretty competitive with Thornmail. It has stronger components, and it also provides +200HP while only having -5AR for an extra 250g.
Overall this item is the stronger of the two when it comes to late game, especially if you don't really need anti-heal or if the enemy team has multiple crit-based carries.
( Thornmail is still preferred vs champions such as Corki/ Ezreal or any other carry that doesn't necessarily build crit).

Kaenic Rookern: This item is by far the strongest MR item in the game, while being reasonably affordable even for supports. Even the base stats on it are very good at mitigating magic damage, but combined with the magic shield it provides, it makes you very hard to deal with for pretty much any AP champion.
The Spectre's Cowl component also recieved a buff to it, which improved its build path.

Force of Nature: Slightly Cheaper than Kaenic Rookern, and has a 4% MS component which is pretty valuable. Normally I opt into this item vs DoT mages ( Anivia/ Cassiopeia/ Brand...etc), where both the mobility and the ramping magic resist is more valuable than Rookern's magic shield.

Note: With Trailblazer/ Dead Man's Plate 1st item you generally will want to build MR for 2nd item, as both of those items are purely AR items.

Bandlepipes: The newest support item, strong but somewhat niche. Good in games where you mainly play around your ADC (carries like Jinx, Yunara, Kog'Maw..etc) or when you have a team comp with a lot of auto-attack reliant champions.

Knight's Vow: Good AR item with a peel oriented (Locket rush) playstyle to keep your main carry alive. For engage oriented builds I don't recommend it, as it just makes you squishier.
This item generally competes with Bandlepipes, and which one you build depends on your ADC, and how much dive threat your opponents have (the more, the better this item is).

Redemption: Niche item (especially now that the item doesn't provide HP anymore), but is still very valuable when you have two melee/frontline heavy comps. (Only opt into it with Locket Rush).

Oblivion Orb: Vs champions that don't rely on aa-s to proc their healing ( Kayn/ Vladimir/ Fiddlesticks are main examples, but it's also very good into healing supports since their target won't necessarily aa you).

Since Thornmail lost it's passive which gave anti-heal based on your CC Oblivion Orb became the more reliable option for Grievous Wounds. This item applies anti-heal on your entire kit for just 800g. The downside is that it makes you somewhat more squishy as neither the component nor the finished item offers any defensive stats.
Also important to note that we don't want to finish the full item until we can't really buy anything else. We only opt into this item for the anti-heal passive, and the 800g component already covers that.

Dead Man's Plate: It's an alternative to Trailblazer, only costs 500g more for 100HP and 15AR. In the current meta, hitting 1st item spikes fast is pretty important, so in my opinion it's rarely worth buying (even in games you are snowballing a lead), but there are games where the 15% slow resist on it can be valuable.

Abyssal Mask: For it's price it has decent stats, and has a strong passive (buffs your own, and your AP carries damage output). The main issue with it is that it rarely keeps you alive for long in teamfights compared to the alternatives, so it sees less and less play.

Frozen Heart: Decent AR item, but suffers from the lack of HP and you generally don't need the mana component from it at the time you are buying it. Some Locket oriented builds can use it, but it's still super niche.

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Honorable mention: Zeke's Convergence: For 2200g has decent stats, and recently it got an ultimate-AH passive which almost makes it competitive.
The biggest issue is that it competes with stronger items (both defensive and utility wise), and you don't really need it's passive dmg/slow.

Matchups: 25.1.1 - Updated in the upper part of the guide to include almost every support matchup. Mage supports are under "Zyra part", generally not big threats if you don't get poked out too hard lvl1, because from lvl2 onwards you have high kill pressure vs these squishy range supports, especially if you have your summoners available as well).

Regarding synergies I didn't go into detail, because Maokai is pretty much playable with every duo thanks to his ability to be played both as a Warden and an aggressive Engage support.

That said, his best duos are generally:

-Mages(APCs) (they want good lockdown/CC - which you have, and you also don't mind having lane partners that allow you to roam more frequently because they can just safely oneshot waves).

-Aggressive ADCs (they also want lockdown/CC to secure early kills in lane and snowball their lead from there.) My personal favourites are Kai'Sa/ Lucian/ Draven(non-mental ones)/ Tristana(when she is meta)...etc

One champion you want to avoid is Twitch. Both of you are relatively weak early game, and he has been in a pretty awful state for a while.

Ban recommendation: Sylas - He has been reasonably strong on recent patches, and he counters you pretty hard. His damage and sustain is pretty high from relatively early stage (when you are still pretty weak as Maokai) and him stealing your ultimate is pretty problematic to deal with in teamfights/skirmishes.

14.4 Update regarding starting ability: Start Q/W. Q is the more standard, W is good for invade/lvl 1 bush plays. E CD is too high currently, so lvl it up 3rd.

Your basic combo is W onto enemy champ, Q towards your ADC (to separate the support and ADC) and ignite them. This usually secures a kill vs most champions, especially if they weren't full HP to begin with. (You can AA after Q/ignite if they still in your range, Aftershock dmg also should go off in time, but the important part is to get the Q direction off properly and in time - your W is a very short CC, so Q has to be pretty quick). Not very hard to learn, 5 mins in Practice Tool should do the trick.

(One thing to note: If enemy ADC has Cleanse, getting this combo off is much harder, assuming they use it properly, so be more thoughtful of your engage in lanes like this.)

Once you have your entire W+Q combo and have Ignite available, there aren't many champions that you don't have kill pressure on with the help of your ADC, but it's especially true vs ranged/squishier supports.

Unless the wave is very close to their tower or you/your ADC is very low, you should always at least consider an all in.
When you have Flash available as well, you can engage from even further, and if you took my advice and equipped Hextech Flashtraption, you can be more "liberal" with your standard Flash usage, as Hexflash from bushes still allows for you to engage from range.
The only drawback of not having Flash up, is you are more easy to gank by the enemy jungler, but since you have your E for vision, this isn't an issue most of the times.

To have more successful engages from the lane bushes, you should get Oracle Lens either by backing around 0:55 after you placed your 1st ward, or after your 1st back.
This will also help in case you want to make a quick gank attempt at mid after your 1st back.

This is not "Maokai-exlusive" but buy Boots on your 1st back. This will unlock your roaming potential to some extent, also helps to rotate faster between lanes/objectives.

Ideally you want Boots, Ruby Crystal, Control Ward at your 1st back, but as long as you get Boots, you are fine.

I generally get Boots of Swiftness (or tier 2 boots) before finishing my 1st item, it helps with better roams/rotation.

Maokai is very good at objective control once he hits lvl 6 because of his ult and saplings, so if your team isn't behind, you should generally look to secure early objectives with your jungler.

Use your saplings to check bushes, and use this to place deep wards in enemy jungle when you have some time to roam.

Maokai makes a great Warden with his Q(knockback ability), always play him according to what your team needs the most (engage/peel).

Since Maokai is a 3 role-flex pick, you can fake hover champions from Jgl/Top lane, to pretend you are picking for one of those roles. This sometimes can help to secure a favourable matchup for your teammates, who otherwise would not get the counterpicking opportunity.

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Hope you find this guide somewhat useful, if you have any questions/feedback feel free to reach out to me in DM/Comment.

GL on the Rift, FunnyBunnyH.