They do speak to the trees, that is a huge part of their society and in 1.0 the Elementals are a very dangerous literal force of nature. I time stamped this to get to the Elemental showing up, but all that happens here is a child lit a tree on fire and...this happens. The first half of this cutscene is the Gridania military, a seer, Papalymo/Yda, and a moogle hurrying to stop this event, and steadily freaking out once they realize the elementals are pissed and we needed the Conjurer mentor to fix it.
https://youtube.com/watch?v=vIpSstzqeWs:89
I believe in 1.0 you have an instance where without a seedseer's intervention, an enraged Elemental effectively removes murders someone using aether to disintegrate them. The Elementals are the original beings who live in The Black Shroud and they are why Gelmorra existed, Gelmorra was an underground city that attempted to squeak out a living away from the Elementals' wrath, but those that would become the Wildwood Elezen made a pact with the Elementals to allow what would become the nation of Gridania to be built.
I know the Elementals and tree spirit shit looks like a whole lot of nothing, because the Elementals effectively do fuck all in post 2.0 FFXIV (it is cited that the calamity has dramatically weakened their strength), but the Elementals in lore and in 1.0 through just having a ton of aether and using what is called the Greenwrath (this is basically a curse that makes you the enemy of the wood which the 1.0 PC in Gridania gets) are an extremely dangerous threat if provoked.
Don't piss off the wood. The reason Gridania is Xenophobic is because they don't want outsiders ruining what they got, and even Kan-E-Senna from what I remember is fairly xenophobic and only budges and changes when Garuda starts wrecking everything in 1.0 and Gridania can't handle her themselves.