According to Wikipedia:
Solidago gigantea is a North American plant species in the sunflower family. Its common names include tall goldenrod and giant goldenrod, in reference to its height of up to 2 m tall, rather large for the genus, smooth goldenrod and late goldenrod. It is a widespread species known from most of non-arctic North America east of the Rocky Mountains. It has been reported from every state and province from Alberta to Nova Scotia to Florida to Texas, and also from the State of Nuevo León in northeastern Mexico.
Solidago gigantea is an herb up to 200 cm (80 inches) tall, sometimes spreading by means of underground rhizomes. They often grow in clumps, with no leaves as the base but numerous leaves on the stem. At the top, each stem produces a sizable array of many small flower heads, sometimes several hundred. Each head is yellow, containing both disc florets and ray florets.
Solidago gigantea is the state flower of Kentucky and Nebraska.