Grief and depression take the shape of a creeping plant in this poem. The speaker describes dark tendrils entering them early, while still young, and slowly taking root in a lonely, fractured heart. From there the poem follows the growth: hidden vines, a fading flame, and finally a harvest of "the blackest fruit," which is the speaker's own heart.
The feeling is heavy isolation. The speaker is cut off from friends who have gone, imagines someone who isn't there, and sits alone on a Ferris wheel, a ride that should be joyful. Small things become overwhelming: a breeze, a burden, a single tear turns into oceans, yet the speaker says "I do not cry," suggesting pain held in rather than shown.
The mood is bleak, trapped, and quietly resigned. The repeated sense of fate ("It was destined") and the line "It can't be done" about pulling the tendrils out leave very little hope by the end.