What is long yellow evil necks in Theodore Roethke's poem "Root Cellar?"
Roethke compares the "long yellow evil necks" to "tropical snakes," imagery that evokes the Biblical allusion of Satan in the Garden.
Instead of a Garden of Eden paradise, the root cellar seems a place of darkness and evil. Instead of one snake in the Garden, we have a slew of snakes in the darkness. Surely, nothing call live in the midst of such suffocating evil.
Ironically, the poem has a positive ending. In the end, nothing gives up breathing; in the midsts of evil snakes, nothing gives up life, not even dirt:
Nothing would give up life:
Even the dirt kept breathing a small breath.
I am not quite sure what you are asking. Are you just asking what the phrase refers to?
If so, the phrase "long yellow evil necks" just refers to "shoots." You can see this because the poem talks first about bulbs and what has happened to them. Then it turns to the shoots. It says that they are dangling and drooping and they look like long yellow evil necks.
If you've ever seen the early growth of some plants, you can kind of see where this imagery comes from. The shoots are all flexible and long like the neck of some sort of monster.