When the new sheaths fall from the culms as they grow. Some bamboos have a distinctive color at sheath fall while others need time for color to develop. They are very tender and may be easily broken. At this stage, they may be harvested for food. In the genus Phyllostachys, this is the groove on the culm formed by the buds under the culm sheath when the new culms grow.
Some bamboos have a distinctive colored sulcas.