Giant ironweed is a perennial plant that is native to the eastern parts of the US where it grows in locations that are consistently moist. It bears smallish bright purple flowers large bracts in late summer to mid-fall providing an unusual pop of tall color in the late season. Giant ironweed grows to a height of about eight feet and a width of about six feet in sunny conditions, and slightly less in shadier spots. It can become weedy, so care should be taken in siting it, and removing unwanted shoots. In an evaluation of ironweeds conducted at the Chicago Botanic Garden, giant ironweed received an excellent rating for growing in local conditions.