He's not about to come out to them. Trees are his power. He will shout in his language to clarify that he doesn't understand them.
He prepared trees in recognizably humanlike forms, for intimidation. A trio of these thump-thumps their way toward them. He tries to say 'no understand'. He's reasonably sure about the 'no' at least.
He recognized 'you'. And says 'no understand you'. Is this a chance to actually learn significant parts of this place's language? "I am Tenno."
He waves and says, "Trava, Jua." Hopefully it's clear enough that's a greeting.
But, visibly, he shrugs and motions at the sun. Can he get some actual language from her? Please? "What is name that?"
Can he get her to name more things?
By motioning at them and asking what that thing's name is. Obvious stuff like 'ground' and 'tree' at first. He makes a fruit, points at a rock. He starts drawing pictures with mobile twigs if her patience lasts that long.
He shakes his head in as confused a way he can manage and says in his own language, "I still don't understand."
Time for visual aids. He makes twig drawing of a person not holding anything going into the forest and then going out the other side holding a piece of fruit. Drawing of people holding swords going into his forest and getting whacked by a drawing of his tree golems until they drop the swords or run away.
She seems amused that he apparently thinks he could take her on. She points at herself, then at the forest, then at herself again, and her stick is suddenly glowing much more brightly than it was. Before she's even done saying anything, she jumps towards him with the glowing stick, trying to stab at him.
3 things happen in quick succession. His wall of wood comes up. He starts flying up as quickly as seems prudent. Trees and tree golems start reaching for Jua.
Jua lets go of the stick before she jumps, and it continues getting brighter and brighter and brighter-
Fates are fast fliers. Tenno is out of reach before Jua grabs at him. They are not that fast, so Tenno only has a few tree canopies and about fifty feet between him and the dangerous stick.
The wall of wood flies after Jua as it glows. There are enough vines and wood gathered near the thuggish-looking ones that he can form a skin-tight shell. The two thugs are immobilized. Also suffocating.