What does Genesis 30:38 mean?
Jacob has created a device he will use to influence whether sheep and goats born in the flock are fully white and black, in turn, or mixed in color. It's important to realize Jacob has made this bargain for the off-color animals at the Lord's direction (Genesis 31:7–12). He has not dreamed this up on his own. The text does not appear to be suggesting that peeled sticks in or near a water source actually cause spotted or striped animals to be born. God is acting supernaturally to bless Jacob by causing a much higher than normal number of mixed-color offspring in response to Jacob's device of placing these sticks in front of the animals he wishes to influence.He has gathered fresh sticks from three specific trees and peeled back the bark to expose the white underneath. This, in fact, may have been part of Jacob's symbolism in using these sticks. The Hebrew term for "white" is laban, making this a fairly direct reference to his cheating father-in-law.
Now Jacob places these sticks in or near the watering places for the flocks, since this is where the flocks also mated.