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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.
Available from Nationwide Book Distributors
 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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