'Myrtle trees' in the Bible

I looked out in the night and saw a man riding on a red horse. He was standing among the myrtle trees in the valley. Behind him were red, sorrel, and white horses.

Then the man standing among the myrtle trees explained, “They are the ones the Lord has sent to patrol the earth.”

They reported to the Angel of the Lord standing among the myrtle trees, “We have patrolled the earth, and right now the whole earth is calm and quiet.”