In Keats's Ode on Melancholy, he writes
neither twist Wolf's bane, tight-rooted, for its poisonous wine;
Why is Wolf's bane described as "tight-rooted"?
It's possible that Keats is using the adjective "tight-rooted" here to keep the tone of the first half of the poem consistent, in that tight-rooted has a connotation of being trapped and imprisoned, not free to roam the world. This is in keeping with the previous mention of the river Lethe, which was associated with lethargy in Greek mythology.