Fringed Gentian
failed rose
Gentians bloom blue-purple, never rose-pink. The flower can't 'try' to be something else—Dickinson is making the plant conscious of its difference.
purple creature
Shift from 'little gentian' to 'purple creature'—once it blooms in its own season, it becomes something powerful and strange, almost animal.
Tyrian
Tyrian purple was the most expensive dye in the ancient world, made from thousands of crushed sea snails. Imperial purple, worth more than gold.
Creator! shall I bloom?
The only quotation in the poem. The gentian speaks directly to God, asking permission—but it's already blooming as it asks.