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 An 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.
 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.
- 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.
Web-notes:
Weed Links
On this site
Reproduced from Common Weeds
of New Zealand:
External Links
 Weedbusters
New Zealand
- Weedbusters is a weeds awareness and education programme that aims to
protect New Zealand's environment from the increasing weed problem.
- AgPest
- A free tool to assist farmers and agricultural professionals in decision-making regarding weed and pest identification, biology, impact and management.
 New Zealand Weeds Key
- An interactive identification key to the weeds of New Zealand. Developed at Landcare Research.
New
Zealand Plant Conservation Network naturalised plants
- Search for information on more than 2500 naturalised and weedy plants.
 New
Zealand Plant Protection Society
- Their main objective: "To pool and exchange information on the biology
of weeds, invertebrate and vertebrate pests, pathogens and beneficial organisms
and methods for modifying their effects."
-
 Massey
University Weeds Database- A site providing information about New Zealand weeds and weed control.
It has a series of pages showing pictures of New Zealand weeds, notes on
identification and control. It also provides information on a university
paper entitled Controlling Weeds.
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