These green bananas will ripen to a bright yellow in 3 to 4 days when their sugars will be fully developed and they will be ready to eat. All bananas are harvested green because, when they are left to ripen on the plant, their texture and flavor deteriorate. The banana tree is considered by botanists to be an herb since it lacks woody tissue. At over 30 feet high, it is undoubtedly one of the largest herbs.