Sweet Flag is a perennial herb 1-4 ft tall, consisting of tufts of basal leaves that emerge directly from a spreading rootstock. These basal leaves are erect and sword-shaped, resembling Iris leaves. They are flattened, smooth along the margins, and have parallel veins. There is often an off-center ridge/indentation along the length of each leaf. Sometimes the base of the leaves or their margins are slightly red. The inflorescence is a cylindrical spadix that is about 2–4 inches in length and semi-erect. This spadix is covered with tiny greenish yellow flowers in a diamond- shaped pattern. Each flower has 6 tepals and 6 stamens. The covering spathe, which is found in many plants of the same family, is absent here. The blooming period occurs from late spring to early summer and lasts about a month. Both the crushed foliage and rootstocks have a pleasant aromatic fragrance. The root system consists of shallow branching rhizomes that are stout and knobby. Tufts of basal leaves occur at intervals along these rhizomes, while coarse fibrous roots develop below. This plant multiplies by its rhizomes. Flowering: March-May.