Identification
This native biennial is our tallest thistle. It is well-behaved and grows to 6 feet or more in height. The leaves are lance shaped and up to 10 inches long near the base of the plant, becoming shorter further up the stem. Lower leaves are usually lobed; mid and upper leaves may have shallow lobes or, more often, just simple teeth. Most lobes and teeth have a spine at their tip. Leaf undersides are covered with fine white hairs (C). The purple flower heads, composed of numerous disk florets, are up to 2 inches across. The urn shaped base of the flower head is covered with small green bracts, each with a light stripe down the middle. Each bract is equipped with a short, straight but soft spine (A,B). The seeds are borne on feathery disks (D).
Found in sun or light shade along trails, roadsides, woodland edges or other sites of disturbance, flowering from August to October. It is uncommon at Fontenelle Forest and Neale Woods in disturbed sites, particularly ones with moister soils.
Of the 4 species identified as of 2024, Tall Thistle is our only native species. Tall thistle, with its spineless stems, less deeply lobed or unlobed leaves and white leaf undersides is usually quite easy to separate from its 3 introduced relatives. Canada Thistle (Cirsium arvense) is the only other thistle with smooth stems, but its smaller flower heads and deeply lobed leaves that are green underneath are quite different.
Tall thistle, a good nectar producer, is visited by many species of bees, moths and butterflies. It is also host species to the Painted Lady butterfly and several moth species.
The content of NatureSearch is provided by dedicated volunteer Naturalists of Fontenelle Forest who strive to provide the most accurate information available. Contributors of the images retain their copyrights. The point of contact for this page is: Roland Barth.