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Book cover - Common Weeds of New ZealandAn Illustrated Guide to
Common Weeds
of New Zealand

 

Senecio jacobaea
ragwort

Family ASTERACEAE

Reproduced from
Common Weeds of New Zealand
by Ian Popay, Paul Champion & Trevor James
ISBN 0 473 09760 5
by kind permission of the
New Zealand Plant Protection Society

Publication or other use of images or descriptive text on these pages is unauthorised unless written permission is obtained from the authors and publisher.
Appropriate acknowledgement of the publication Common Weeds of New Zealand must always be given.

Available from Touchwood Books

Senecio jacobaea - ragwortRosette-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.

  • Flowers Golden-yellow, about 2 cm in diameter, with golden-yellow disk florets, and about twelve yellow ray florets, in compact flat-topped terminal inflorescences. Flowers Nov-Apr.
  • Fruit Rounded achenes about 2 mm long, with a pappus of simple hairs up to 5 mm long, not forming a 'clock'.
  • Leaves Rosette of dark green, pinnately lobed leaves 4-8 cm long with large blunt terminal lobes. Stem leaves deeply cut, stalkless, clasping the stem, with no broad terminal lobes. Leaves often with purple colouring on the underside.
  • Stems Purplish, erect, ridged, densely woolly towards the top, becoming smooth lower down. Stems leafy, branching, 50-120 cm tall.
  • Roots Fibrous.

Habitat

Pastures, waste places, open forest, swamps and river-beds.

Distribution

Weed of cattle pastures throughout New Zealand where annual rainfall exceeds 800 mm, also in the Chatham Islands, but eradicated from the Kermadecs. Originally from Europe and western Asia.

Comments

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. 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. Several insects have been brought into NZ in attempts to control this species. Currently, the ragwort flea beetle (Longitarsus jacobaea) is looking very promising. Ragwort is subject to Pest Plant Management Strategies in most regions of NZ. Details are available from individual regional councils or unitary authorities. Has been regarded as noxious in NZ since 1900.

Related species

Marsh ragwort (Senecio aquaticus) is shorter, with more open inflorescences, less-dissected leaves and less hairy achenes. It flowers Jan-Jun, and is found in wet-lying areas at Mercer and Levin in NI, and in Nelson Province and Southland in SI.

Derivation of botanical name

Senecio (Lat.) = old man, from the fluffy white seed heads; jacobaea from St. James (Jacobus), one of the Twelve Apostles.

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Last updated: July 13, 2014