The yellow iris (Iris pseudacorus) grows in wet habitats and is an impressive sight when it blooms in June–July. Vanhankaupunginlahti is the most important yellow iris habitat in Helsinki.
Yellow iris is a popular garden ornamental plant. In addition to the natural yellow-flowered variant, white-flowered and flore pleno cultivars are also available. The plant is poisonous, but its roots have traditionally been used to treat wounds. Being rich in tannic acid, the roots have also been used in the tanning of leather.