T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network


Jacobaea vulgaris (Yellow Ragwort)

Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Asterids
Order: Asterales
Family: Asteraceae
Subfamily: Asteroideae
Tribe: Senecioneae
Genus: Jacobaea
Binomial name: Jacobaea vulgaris
Formerly: Senecio Jacobaea
Common name: Ragwort

Derivation of the orginal botanical name is from Senecio (Lat.) = old man, from the fluffy white seed heads; jacobaea from St. James (Jacobus), one of the Twelve Apostles.
Ragwort is a noxious weed It is a rosette-based, robust biennial or perennial with characteristic unpleasant smell when bruised. Leaves dissected into large lobes.
Flower stem up to 1.2 m tall, bearing bright yellow composite flowers, each 2 cm across, in flat-topped clusters. The flowers are golden-yellow, about 2 cm in diameter, with golden-yellow disk florets, and about twelve yellow ray florets, in compact flat-topped terminal inflorescences. It flowers Nov-Apr and the fruit is rounded achenes about 2 mm long, with a pappus of simple hairs up to 5 mm long.
The leaves are a rosette of dark green, pinnately lobed leaves 4-8 cm long with large blunt terminal lobes. The stem leaves are deeply cut, stalkless, clasping the stem, with no broad terminal lobes. Leaves often with purple colouring on the underside. Stems are leafy and branching up to 50-120 cm tall.
Pollination is by a wide range of bees, flies and moths and butterflies. Over a season, one plant may produce 2,000 to 2,500 yellow flowers in 20 to 60 headed, flat-topped corymbs. The number of seeds produced may be as large as 75,000 to 200,000.
The plant forms a rosette in its first year, and usually flowers and then dies in its second year, unless its growth is interfered with, when it can become a multi-crowned perennial.
It is poisonous to cattle and horses, but less so to sheep. Usually ignored by cattle and horses but kept in check by sheep. The poison affects the liver, can be very slow acting in sheep and its effects can be confused with those of facial eczema.

Biological control by the introducing of Longitarsus jacobaeae is a species of flea beetle known as the tansy ragwort flea beetle. The beetle is most effective when used in conjunction with the cinnabar moth (Tyria jacobaeae), another ragwort biocontrol agent.



 
 
This photo was not taken on the Te Henui walkway but was included to show how invasive it can be on farm land
Photo taken in the Buller area