#that he taught Arya the stars in exchange for flower knowledge lol

[thelustybraavosimaid]

Canonically and established in Sansa's very first AGoT chapter, Arya absolutely loves flowers. She goes out of her way to pick some (though they turned out to be poisonous and rash-inducing) for Ned:

Dense thickets of half-drowned trees pressed close around them, branches dripping with curtains of pale fungus. Huge flowers bloomed in the mud and floated on pools of stagnant water, but if you were stupid enough to leave the causeway to pluck them, there were quicksands waiting to suck you down, and snakes watching from the trees, and lizard-lions floating half-submerged in the water, like black logs with eyes and teeth.

None of which stopped Arya, of course. One day she came back grinning her horsey grin, her hair all tangled and her clothes covered in mud, clutching a raggedy bunch of purple and green flowers for Father. Sansa kept hoping he would tell Arya to behave herself and act like the highborn lady she was supposed to be, but he never did, he only hugged her and thanked her for the flowers. That just made her worse.

Then it turned out the purple flowers were called poison kisses, and Arya got a rash on her arms. Sansa would have thought that might have taught her a lesson, but Arya laughed about it, and the next day she rubbed mud all over her arms like some ignorant bog woman just because her friend Mycah told her it would stop the itching. (Sansa I, AGoT)

and tells Sansa that she counted thirty-six different types of flowers that she had never seen before:

Arya shrugged. "Hold still," she snapped at Nymeria, "I'm not hurting you." Then to Sansa she said, "When we were crossing the Neck, I counted thirty-six flowers I never saw before, and Mycah showed me a lizard-lion." (Sansa I, AGoT)

There's a Jon chapter where he looks at the scenery in the Skirling Pass and describes the environment partially like so:

Yet even so, Jon Snow was not sorry he had come. There were wonders here as well. He had seen sunlight flashing on icy thin waterfalls as they plunged over the lips of sheer stone cliffs, and a mountain meadow full of autumn wildflowers, blue coldsnaps and bright scarlet frostfires and stands of piper's grass in russet and gold. (Jon VI, ACoK)

Jon is obviously no fool, and very far from clueless, but I do have a sweet headcanon - that Jon and Arya snuck out to the wolfswood (or, even simpler to explain, into Winterfell's glass gardens) and Arya taught Jon the names of some flowers - which is how he knew the names of the scarlet frostfires, the blue coldsnaps, and the piper's grass he saw beyond the Wall. Arya's enthusiastic about plants and they've spent a lot of time together anyway lol