Perhaps the most prominent literary device seen in Theodore Roethke's poem "Root Cellar" is imagery.
Imagery, according to eNotes, is
the forming of mental images, figures, or likenesses of things. It is also the use of language to represent actions, persons, objects, and ideas descriptively. This means encompassing the senses also, rather than just forming a mental picture.
Therefore, it is apparent that Roethke uses imagery in his poem when phrases such as "mildewed crates," "roots ripe as old bait," and "slippery planks" all appeal to many different senses other than just visual alone.
Other poetic, or literary, devices used in the poem are alliteration and assonance.
Alliteration is the repetition of a consonant sound within a line of poetry. Examples of alliteration in the poem are as follows:
1. "Dank as a ditch"-- "d" is repeated.
2. "Bulbs broke out of boxes"-- "b" is repeated.
3. "Roots ripe"--"r" is repeated.
Assonance is the repetition of a vowel sign within a line of poetry. Examples of assonance in the poem are as follows:
1. "Out of boxes"-- "o" is repeated.
2. "Chinks in"--"i" is repeated.
3. "Shoots...drooped"--"oo" is repeated.
One last poetic device found in the poem is a simile. A simile is a comparison made between two things using the words "like" or "as." (Be careful in determining this though, not all use of the words "like" or "as" denote a comparison.)
In "Root Cellar," the simile is found in the following lines:
Shoots dangled and drooped,
Lolling obscenely from mildewed crates,
Hung down long yellow evil necks, like tropical snakes.
The comparison made is between the shoots which hang down to tropical snakes.