jacobaea

Jacobaea is a genus of flowering plants in the family Asteraceae. The genus was first described in 1816. Species within this genus are found in Europe, Asia, and Africa. They are typically herbaceous plants, though some can be shrubs. Jacobaea species are characterized by their composite flower heads, which are usually yellow or orange, and their deeply lobed or pinnate leaves.

Commonly known as ragworts, many Jacobaea species are widespread weeds. For example, Jacobaea vulgaris, formerly Senecio jacobaea, is a well-known noxious weed in many parts of the world, particularly in pastures where it is toxic to livestock. Other species, such as Jacobaea maritima, are cultivated as ornamental plants for their attractive silvery foliage.

The taxonomy of Jacobaea has been subject to revision, with many species formerly placed in the genus Senecio now being reclassified into Jacobaea. This reclassification is based on molecular phylogenetic studies. The genus name honors the biblical figure Jacob. Plants in this genus reproduce by seeds and can spread rapidly, especially in disturbed habitats. Their ecological role can vary, with some species contributing to biodiversity while others pose agricultural challenges due to their invasive nature and toxicity.