Flax grows to a height of about 24 to 36 inches. The plant has a tap root which may penetrate to 40 inches if growing conditions are good. In years when moisture is available the maturation period may extend until a hard frost kills the crop. In a wet fall new flowers are often observed until frost. Flax is a self pollinated crop.
Seed is produced in a boll or capsule.
A complete boll can have 10 seeds, but most bolls will have fewer, averaging around six seeds. Seed color can be brown, golden, or yellow. The seed is covered with a mucilaginous coating. This coating becomes sticky when wet. During a wet harvest, this coating may discolor, giving the seed a weathered appearance and a reduced test weight.