Aurora
Bronze and blaze
The northern lights—aurora borealis. Dickinson saw them in Amherst in 1851 and 1882, rare events at that latitude that caused local sensation.
Preconcerted with itself
Self-choreographed, self-sufficient. The aurora doesn't perform for anyone—it just is. Notice the contrast with Dickinson's own performance anxiety about poetry.
Strut upon my stem
Flower metaphor—she's a bloom on a stalk. The verb 'strut' is absurd for a rooted plant, which is the point. Her inflation is ridiculous.
Competeless show
Without competition, unrivaled. Dickinson coined this word—it doesn't exist in standard English. The aurora's display has no equal.
Island in dishonored grass
A grave mound. 'Dishonored' because unmaintained, overgrown. She'll be a forgotten burial plot that only wildflowers visit.