BOLLED (גִּבְעֹל, H1499). A rare word referring to a flower bud or seed pod, and used in Exodus 9:31 KJV of flax. The rendering “bolled” is archaic, meaning “having bolls” or “bearing pods,” hence “in seed,” though the Heb. could refer equally to the flower. The RSV rendering “in bud” seems inadequate.

International Standard Bible Encyclopedia (1915)

Hence, "in bloom," and so rendered, in the Revised Version (British and American), of flowering flax (Ex 9:31).