Wild Artichoke or Artichoke Thistle Cynara cardunculus

Weed management guide
Wild Artichoke or Artichoke
Thistle Cynara cardunculus
© Tracey Hardwicke
Overview
Description
Wild Artichoke is a declared plant under the Natural
Resources Management Act 2004.
Stems: erect, strongly ribbed, covered with cottony down,
branched near the top. Generally only one stem develops from
each crown but up to eight may be produced.
Originating from Mediterranean Europe, Wild Artichoke was
introduced into Australia as a salad plant and potential fodder.
Since then it has become widespread.
It’s an erect perennial herb to 2 m high, although commonly
0.75–1.5 m. Reproducing from perennial taproot and by seed.
Favouring higher rainfall districts, Wild Artichoke occurs as a
weed of poorer pastures and neglected areas. In South Australia
there are dense infestations north and south of Adelaide, mainly
on the western aspects of the Mount Lofty Ranges and
extending to Port Augusta.
As a declared plant under the NRM Act its sale or transport
is prohibited throughout the state and landholders are required
to control Wild Artichoke on their properties. The best time
to control is winter and early spring.
Leaves: greyish-green above, whitish below because of dense
mat of white hair. Rosette leaves to 90 cm long, 30 cm wide;
stem leaves smaller. All leaves deeply divided almost to the
mid-rib, yellow-orange spines along margins. Leaf stalks ribbed
and with spines.
Flowers: blue to purple in large, almost globular heads
produced singly at the ends of branches. 7–13 cm diameter
including the numerous encasing stout bracts, each tipped with
a rigid spine. About 16 heads on each plant but occasionally
more than 50.
Seed: brown or black, streaked lengthwise, 6–8 mm long,
smooth, 4-sided. Pappus of feathery hairs to 4 cm long.
Roots: large fleshy taproot to 2 m long.
2 | Weed management guide
Ecology
Wild Artichoke is not restricted to any particular type of soil but
is most competitive on heavier clay soils. It generally requires
rainfall above 450 mm a year to do well.
Seeds may germinate at any time of the year but most do so
after autumn rains. Seedlings develop slowly through winter
before making rapid growth in spring. The best time to control
is winter and early spring.
A deep taproot develops in the first year.
Flower stems emerge from the crown by October and, as they
develop, the lower leaves die off. Plants flower during summer
and individual plants live for many years.
Spread is almost entirely by seed. Up to eight flower stalks
per plant can form, each containing approximately 200 seeds.
Pieces of cut root are capable of producing new plants but this
is important only where infested areas are cultivated. Seed
is spread by wind, sheep, cattle, water, mud, birds and mice.
Impacts
Once established, Wild Artichoke dominates the vegetation
of an area and excludes native fauna from infested areas. The
dense foliage of large plants shades out most pasture and native
groundcover species as well as drawing moisture and nutrients
from the soil. The spiny nature of the plant deters sheep and
cattle from grazing.
Unmanaged plants quickly form thickets which smother native
and desirable vegetation and can hinder property access and
use. Enjoyment of native and amenity areas can then be restricted
by Wild Artichokes.
Management and control
Long-term control of Wild Artichokes requires an integrated
approach using as many control methods that suit the situation
as possible. Controlling Wild Artichokes is not a short-term activity.
Follow up control after the initial work has been undertaken
is essential. It may take many years before a successful level
of control is achieved. The key to plant control is destroying
the taproot which may grow to 2 metres deep.
Landholders should first undertake control of individual or smaller
isolated patches of Wild Artichoke, working back in towards the
larger infestations.
Only by reducing and eventually eliminating the seed bank can
Wild Artichoke be considered removed from a site.
A semi-mature Wild Artichoke © Tracey Hardwicke
strengths/rates can result in leaf burn off but not affect the
taproot, so the plant survives. For good results the plant’s entire
leaf needs to be treated with the correct herbicide and strength.
Landholders should always read the label of any herbicide to ensure
it is suitable for its intended purpose and can be used safely.
Mechanical
In all circumstances after mechanical control has taken place
some form of follow up control of regrowth and seedlings will
be required. This follow up control will need to be maintained
for a number of years.
Hand grubbing of scattered plants is practical but much of the
taproot must be removed or new growth develops from the
cut surface. Slashing plants in flower stalk formation, if timed
before flower heads are fully formed, will restrict flowering
and seed production.
Whichever mechanical option is used consideration needs
to be given to any soil disturbance so that it does not cause
any undue erosion issues.
Burning
In circumstances where it is safe, fire may be an option to burn
patches of Wild Artichoke down to ground level. To destroy
seed the fire needs to have sufficient fuel levels to generate
enough heat.
Foliar spray for best results from June to November while the plant
is still in a rosette growth stage before the flower stalk emerges.
Plants can be treated at all times if green and actively growing.
Burning will not adequately control Wild Artichoke and other
methods will be required to completely destroy infestations.
Care is especially needed with follow up control after fire is
used, as fire will stimulate seed germination which may result
in masses of seedlings appearing on the newly exposed
infestation area.
Herbicides must be able to translocate from the leaves to the
taproot for effective control. Incorrect herbicides, use or
Landholders should be aware of any fire restrictions before
using fire as a control method.
Herbicides
400mlL/100L
140ml/100L
Surfactant
Surfactant
Surfactant
Surfactant
Surfactant
Surfactant
Surfactant
Required
addition
Spot spray
Boom spray
Manual
removal
Spot spray
Boom spray
Spot spray
Boom spray
Spot spray
Application
method
Apply at rosette stage.
Refer to drift warnings on the label.
Hormone type treatment, use with caution near sensitive crops.
Crop and pasture rates, refer to label.
Apply at rosette stage.
Non crops areas, fallow, rights of way.
Refer to drift warnings on the label.
Hormone type treatment, use with caution near sensitive crops.
Ensure that the root system is removed to a depth of 150 mm.
Apply at rosette stage.
Non selective, avoid contact with desirable plants.
Apply at rosette stage.
Non selective, avoid contact with desirable plants.
Spray prior to flowering.
Spray prior to flowering.
Use double rate at flowering.
Soil residual. Do not use near desirable vegetation or in waterways.
Do not apply near susceptible crops.
Comments
Source: 2013 Weed Control Handbook for Declared Plants in South Australia. This publication offers advice on suitable herbicides and rates. A copy of the handbook is available at www.pir.sa.gov.au.
I
MCPA 250
I
M
2.4L/ha
MCPA (250g/L)
Roundup®
Glyphosate
(450g/kg)
M
100ml/100L
2.1L/ha
Roundup®
Glyphosate
(450g/kg)
I
1.6L/ha
MCPA 250
Kamba 500®
Dicamba (500g/L)
I
125ml/100L
MCPA (250g/L)
Kamba 500®
Dicamba (500g/L)
I
Application rate
(with water
unless indicated)
Grub plants
Tordon®75-D
2,4-D (300g/L) +
picloram (75g/L)
Herbicide
group
Manual removal
Example
of product
names
Herbicide
Wild Artichoke herbicide treatments and rates
Weed management guide | 3
4 | Weed management guide
Grazing
Goats may graze Wild Artichokes but only on young plants or
on the new soft, fresh growth on adult plants before spines are
formed. Grazing will not remove Wild Artichokes but it can be
moderately successful in suppressing the flowers forming seeds
and can be useful when used in conjunction with other methods.
Plants should not be over grazed prior to the herbicide
application. Check herbicide label for advice and stock
withholding periods.
areas. Creeks and rivers can also act as pathways for seed spread
so Wild Artichoke should be kept away from watercourses to
prevent seed being carried downstream.
Biological control
No biocontrol agents are currently available in Australia mainly
due to the closely related species, Globe Artichoke (Cynara
scolymus) which is grown commercially in Australia.
Control timing
Hygiene
Good hygiene procedures will prevent new seed being
introduced to areas free of Wild Artichoke or areas where active
control is being undertaken. All vehicles, machinery, tools and
footwear should be checked for soil or mud and cleaned before
entry into Wild Artichoke-free areas and before leaving infested
This chart shows the optimum time for each control method and
may be used as a guide to help with planning control programs.
However local conditions should be taken into account to ensure
control will be effective. Herbicides are best applied when the
plants are actively growing.
Timing guide for Wild Artichoke control activities
Method
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Mechanical
Burning
Grazing
Herbicide – foliar spraying
Natural Resources Centres
Further information on the management and control of Wild
Artichoke contact your local centre.
Gawler
E: DEWNR.AMLRGawlerOffice@sa.gov.au | T: (08) 8523 7700
Lobethal
E: DEWNR.AMLRLobethalOffice@sa.gov.au | T: (08) 8389 5900
Willunga
E: DEWNR.AMLRWillungaOffice@sa.gov.au | T: (08) 8550 3400
Need more information?
Visit: www.naturalresources.sa.gov.au/
adelaidemtloftyranges or
www.pir.sa.gov.au/biosecurity.
Licensed under Creative Commons Attribution 3.0 Australia License www.creativecommons.org/licenses/by/3.0/au
Copyright owner: Crown in right of the State of South Australia 2014
While every reasonable effort has been made to verify the information in this fact sheet use of the information contained is at your sole risk. The department
recommends that you independently verify the information before taking any action.
FIS 92659
Wild Artichoke flower © Wikimedia Commons, BotBln