Sea aster is a type of wild flowering plant, Aster tripolium, that is native to coastal areas of northern and western Europe, particularly salt marshes and estuarine areas. It is also found in some areas of eastern North America. It has small, simple flowers that range from pale purple to white or yellow, though some flowers are streaked with two or more of these colors. It is seldom cultivated as a bedding or garden plant due to the difficulty of reproducing its preferred growing conditions. Once regarded as a low-quality food, eaten only during times of famine, it has gained popularity as a food and appears in supermarkets in some parts of the world where it grows, particularly in Great Britain.
In its native environment, sea aster is a low growing, herbaceous, perennial flowering plant. It is classified as a perennial as it lives beyond its first year, but it is short lived, and individual plants rarely last beyond three or four years. Each plant, which can reach up to 3 feet (1 m) tall, can have many flowers, each borne individually at the end of short-branched stems, which grow in clusters at the end of larger stems. They have a daisy-like appearance with a yellow center surrounded by thin petals of pale blue, purple, yellow, or white. Some varieties can have rayed petals of multiple colors.
These flowers grow along ocean coastlines and in salt marshes and estuarine areas. They can form large colonies and can tolerate, and actually prefer, very wet and salty conditions, making them somewhat unsuitable as bedding or garden plants. They bloom from late summer to early fall and are sometimes called "summer's farewell" as they are one of the last flowers of the season in many areas, which also makes them an important source of late season food for several butterfly species.
Humans have long known that the long, thin, and robust dark green leaves of the sea aster were edible and at one time were considered a low quality food only consumed by peasants and in times of famine.They have gained popularity, however, as a type of cooked green and are considered a delicacy by many and collected by foragers. They are even found sometimes in supermarkets and farmer's markets, sold as a gourmet green. Sea aster greens are cooked before eating and are usually prepared like other cooked greens, either sautéed or steamed.