Centaurea macrocephala

Appearance

This species is a perennial herb with mostly unbranched stems reaching up to 170 centimeters tall. The leaves are variable in shape and size. Those near the base have oval blades borne on petioles and those higher on the plant have shorter, narrower blades. The flower heads are solitary atop the stems and have arrays of small leaves around the bases. The heads are 2.5 to 3.5 centimeters wide. The somewhat rounded head is covered in layers of phyllaries with fringed tips and sometimes spines. The head contains many yellow florets. The fruit, including its pappus, can be well over one centimeter long.

Behavior

In its native range in the Caucasus, this plant grows in mountain meadows. It is a summer-flowering subalpine species. It thrives as an introduced species in many types of moist temperate habitat, especially areas dominated by perennial herbs. It can grow in disturbed areas.

Habitat

As the plant has been transported around the world for ornamental use it has taken hold as an introduced species in several areas. It is a casual garden escapee in parts of Europe and North America. It has only become a troublesome noxious weed in a few areas, notably Washington State in the United States, where it is prohibited to buy or sell the species. Its invasive nature is best seen in garden environments, where it is more aggressive than most other ornamental plants and can become a "garden thug".

Uses

This is a well-known ornamental flowering plant. It has been a garden flower for over 200 years, being introduced to the United Kingdom and United States in the early 19th century. Thomas Jefferson obtained seeds from the nurseryman Bernard McMahon and planted them at Monticello.

In gardens it can be placed at borders or corners, where it will form clumps. It is used as a cut flower for its large, rounded heads with long yellow florets, and it can be used as a decorative dried flower. This is the largest ''Centaurea'' in cultivation and is easily recognized.