That three skull difficulty rating in your quest log in Avowed sure makes it seem like you should wait a long time to approach the Delemgan Queen to close out The Animacy Method quest to recruit Giatta. It is a tough one if you're going to fight your way through her hordes of awful Delemgan guards. But be not afraid of the plant slashing attacks—there is a stealth route.
I highly recommend going the peaceful route because this quest is what's standing between the Envoy and recruiting Giatta. If you wait until you're ready to take the delemgan glade by force, you'll have missed out on having her in your party for basically your entire time in Emerald Stair.
As he's sending you off into certain danger against hostile tree people, Monto Pastor suggests that delemgan queens can actually be reasoned with. If you want to get the adragan heart peacefully he suggests you "try not to kill her guards." Not the most specific advice. Here's how to reach the Delemgan Queen without alerting her entire hostile grove:
How to approach the Delemgan Queen peacefully
To meet the Delemgan Queen without fighting, you're going to need the stealth skill Shadowing Beyond from the Ranger skill tree. It sure seems like you can pull off the peaceful route without it, but frankly Avowed's stealth system is so finicky that I spent an hour trying to make it work and eventually gave in. Just grab Shadowing Beyond in your next level up.
Head towards the Delemgan Glade on the western edge of the Emerald Stair map, towards the central bridge you can see leading to the peninsula. You'll face a little less initial combat if you approach from the northeast at the Grim Wetlands party camp instead of from Tama's cabin. Unlock the Delemgan Glade Beacon fast travel point just before the bridge and pause here to get ready.
All the delemgan so far have been fair game to fight but you'll need to hang up your blades once you cross the bridge. Don't kill any of the delemgan called "Queen's Shield" or "Queen's Fury," and so on. Enter stealth by pressing C to crouch and approach the path that heads directly into the glade. Once you get close to a Queen's Shield and a few sporelings together on the path, use your Shadowing Beyond skill.
While hidden, stand up and walk straight into the glade towards the central, tree-covered structure where you can see the delemgan queen summoning a big yellow ball of magic. Remember that Shadowing Beyond is going to drain your essence over time, so keep an eye on that. Drinking an essence potion won't count as a combat action, so chug one if you need it. You'll just need to reach the archway leading to the room where the Delemgan Queen is standing surrounded by her guards.
If you want to attempt the approach purely on stealth skills without magic, you can crouch in tall grass to be hidden from enemies. Work your way between patches of grass past the Queen's Shield and head up a path to the right above the main clearing. You'll really have your work cut out for you avoiding the sneaky sporelings that pop out of the ground and initiate combat if you aren't careful. Toggling Avowed's third person view can help you spot those troublemakers ahead of time but even still I found the process way too much of a headache and went with the ranger stealth solution.
How to convince the Delemgan Queen to give up the adragan heart
Thankfully Monto wasn't lying and it turns out that the delemgan queen really is quite reasonable. She's not bothered at all giving up the adragan heart as long as you haven't started beef with her aggressive tree kids.
Whether you politely listen to her story or get a little abrupt telling her that you "won't leave without it," she'll give up the heart willingly. You don't even need to pass any skill-based speech checks. It's just getting an audience with the queen that's such a living nightmare.
