Shrub, or plant
'A shrub' or 'plant,' as in Genesis 21:15, denotes perception, but so little that it is hardly anything, in same way as 'trees,' but to a lesser degree. So 'to be cast under one of the shrubs,' signifies being destroyed regarding truth and good, to the point of desperation.
(References: Arcana Coelestia 2682 [1-3])
Genesis 15:9
9
He said to him, "Bring me a heifer three years old, a female goat three years old, a ram three years old, a turtledove, and a young pigeon."