Solidago gigantea

Several North American species of goldenrod family have been introduced to Finland as ornamental plants. They are perennial, rhizomatous, tall grasses that often form extensive stands. The most common of them is the Canadian goldenrod (Solidago canadensis). In Finland, the Canadian goldenrod, the tall goldenrod (S. altissima) and the giant goldenrod (S. gigantea) have been regulated as invasive alien species. The giant goldenrod is less common than the Canadian goldenrod, and there are no confirmed sightings of the tall goldenrod in Finland. In addition, cross-bred varieties of goldenrod for horticultural use (S. Canadensis -Group) have been found as fugitives in Finland, but they are not regulated as invasive alien species.

North American goldenrods are perennial and often form extensive growths; the growths are very long lived on their rhizomes. In addition to home yards and gardens, their sites include a wide variety of habitats modified by humans, for example wasteland, river, road and rail banks, and abandoned farmland.

Goldenrods reproduce both from seed and vegetatively from rhizome bodies. They seed profusely: a single shoot can produce more than 10,000 seeds. Pubescent seeds spread over long distances with the winds. The stiff stalks of goldenrods persist well into the winter, allowing the seeds to spread along the surface of snow. Invasive goldenrods can also easily spread from place to place with plant debris and soil containing fragments or pieces of rhizome.