The tall sunflower (Helianthus giganteus) is aptly named, being capable of growing to heights of over three metres (2). The genus name, Helianthus, is derived from the Greek words helios and anthos, meaning ‘sun’ and ‘flower’, while the species name, giganteus, means ‘very large’ (3). The common and scientific names of this species refer only to the great heights to which it can grow, as the conspicuous, yellow flowers are actually relatively small (2). The flower heads are usually between 4 and 8 centimetres wide with 10 to 20 yellow petals (3). There can be up to 12 heads on each tall sunflower plant, with more than 60 disc florets on each head and dark brown or black anthers and appendages (4). The stems are hairy and a dull reddish-purple colour (4) (5). Leaves that grow lower down on the stem are opposite one another, whilst higher leaves grow alternately (3) (6).
- Height: over 3 m (2)