Agriculture Victoria (2020). Artichoke thistle. Victoria State Government. Available at: https://agriculture.vic.gov.au/biosecurity/weeds/priority-weeds/artichoke-thistle . [Accessed 26/11/2020].
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Artichoke Thistle (Cynara cardunculus) is an upright, stout, long-lived (perennial) herb that usually grows to a height of 60-150 cm but has been known to reach 2 metres tall. The basal rosette leaves (radial cluster of leaves at base, and the first to appear) are very large (up to 120 cm by 30 cm). A single stems subsequently grow from the basal rosette, is thick, rigid and very obviously ribbed lengthways, covered in a cottony hairs, and are often branched in the upper parts. The leaves that occur along the stem are comparatively small (10-50 cm long). All leaves are deeply divided and have greyish-green upper surfaces and lower surfaces that appear woolly due to a dense covering of hairs. The tips and edges of the leaves bear stout yellowish-orange sharp spines 0.5-2 cm long.
Large, single flowers are found at the tips of the branches on thick stalks. The flower head (capitulum) consists of many blue, pink or purple (rarely white) florets 50 mm long attached to a fleshy base and enclosed within numerous bracts (modified leaves). The bracts are purplish in colour, tapering to a stout, flattened spine. The capitulum is almost round in shape and 5-13 cm wide. Each flower produces a seed with many seeds produced on a flower-head.
The fruits or 'seeds' (cypselas) are 6-8 mm long and topped with large feathery hairs which are 25-40mm long and readily fall off. They are light grey, brown or black in colour and sometimes have lengthwise streaks (Navie 2004; Williamson et al. 2007).
For further information and assistance with identification of Artichoke Thistle, contact the herbarium in your state or territory.
Blue or Purple or Pink or White.
Artichoke Thistle (Cynara cardunculus) is mostly found in temperate regions, but may also be found in sub-tropical and semi-arid environments. It prefers black basalt soils in Victoria and red-brown earth in South Australia (Parsons and Cuthbertson 2001; Navie 2004). It commonly infests pastures, but is also a weed of crops, grasslands, open woodlands, roadsides, gardens and disturbed sites (Navie 2004).
Artichoke Thistle (Cynara cardunculus) can easily be confused with the commonly cultivated Globe Artichoke (Cynara cardunculus subsp. flavescens) [as Cynara scolymus]. The globe artichoke is a cultivar of Cynara cardunculus subsp. flavescens, bred for lack of spines and fleshy involucral bracts. It is propagated vegetatively and progeny derived from seed tend to revert to wild forms (Bean et al. 2014). Artichoke Thistle has broad flower-head bracts which are flattened and pointed, tapering to short, stout spines. Globe Artichoke also has broad, flat bracts, but they are not very pointed and are spineless.
Artichoke Thistle is also somewhat similar to Variegated Thistle (Silybum marianum). Artichoke Thistle has broad flower-head bracts which are flattened and pointed, tapering to short, stout spines. The leaves of Variegated Thistle are variegated, whereas those of Artichoke Thistle and Globe Artichoke are greyish green. Variegated Thistle also has flower-head bracts with broad bases and curled upper parts ending in long, narrow spines (Navie 2004).
Artichoke Thistle can also be confused with other 'thistles' such as Spear Thistle (Cirsium vulgare), Perennial Thistle (Cirsium arvense), the Slender Thistles (Carduus pycnocephalus and Carduus tenuiflorus), Nodding Thistle (Carduus nutans) [as Carduus nutans subsp. nutans], Scotch Thistle (Onopordum acanthium) and Illyrian Thistle (O. illyricum). However, these species can all be easily distinguished from Artichoke Thistle by their 'winged' stems (Navie 2004).
Artichoke Thistle (Cynara cardunculus) is largely known as a pest of agricultural areas (particularly pastures), and a weed of crops and disturbed sites. It invades natural habitats most commonly in grasslands, open woodlands, as well as roadsides, gardens, waste areas and disturbed sites. It can easily dominate the vegetation in densely infested areas, smothering most desirable ground-dwelling plants.
Agriculture: Artichoke Thistle is a serious weed of permanent pastures, and occasionally Lucerne. Once established, it dominates the vegetation of an area, out competing and smothering most desirable pasture species drawing most moisture and nutrients from the soil (Parsons and Cuthbertson 2001). The spiky nature of the plant deters grazing by stock and restricts their movement in dense infestations, but animals will eat the leaves when hungry and no other feed is available. It has low nutrient value and may cause stomach impaction and mechanical injuries, but is not poisonous (Government of South Australia 2014).
Native ecosystems: Artichoke Thistle can invades natural habitats, for example, grasslands, open woodlands, and wetlands and riparian areas in drier regions, smothering native ground-dwelling plants. In Victoria, it invades lowland grassland and grassy woodland, and riparian vegetation (Carr et al. 1992).
Urban areas: Can invade disturbed sites and gardens, and is reported to cause dermatitis in some people.
Artichoke Thistle (Cynara cardunculus) disperses via seeds. Established plants re-grows each year from a long-lived underground crown (where stem and root join) and taproot. The seeds are dispersed by wind, but they do not travel far, as they are heavy. Seeds can be blown up to 20 m away from the parent plant, but most fall within a few metres. They are also spread by animals, water, vehicles and in mud, dumped garden waste and cut flower arrangements (Parsons and Cuthbertson 2004; Navie 2004).
Pieces of cut root are capable of producing new plants, but this is only of concern in areas of cultivation, where there is a lot of root disturbance from mechanical activity (Parsons and Cuthbertson 2004).
Artichoke Thistle (Cynara cardunculus) flower heads were once sold as New Year's ornaments in Melbourne. It is unknown if this was the method of introduction into Australia. The earliest record is from Adelaide in 1839 and it was sold as a culinary plant in a Tasmanian nursery in 1845. It had become naturalised in South Australia by 1879 (Parsons and Cuthbertson 2001).
Artichoke Thistle has some importance to the honey industry as the plant has an abundant supply of pollen (Parsons and Cuthbertson 2001). Flower heads can be eaten by humans in a similar fashion to the heads of Globe Artichoke, and they have also been used in cut flowers arrangements (Williamson et al. 2007).
Artichoke Thistle (Cynara cardunculus) can be controlled by herbicides, and young plants may be removed by physical means, with cultural and grazing by goats also an option.
Chemical control: Herbicides can effectively kill Artichoke Thistle and should be applied from September to November while the plant is still in rosette or in early flower-head stage (Parsons and Cuthbertson 2001) Spot or boom spraying is only effective during autumn and winter and usually has to be undertaken twice. Use chemicals that are registered for Artichoke Thistle and use according to the label. Also see DiTomaso, et al. (2013); DPI NSW (2019); Invasive Species Unit, Biosecurity SA. (2018).
Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au
Physical control: Artichoke Thistle can be removed by physical grubbing when there are small infestations. Care must be taken to remove most of the tap root.
Cultural: Cultivation can also be effective, but new growth will appear from seeds and roots and the process must be repeated until no new growth appears. This may take 2 or 3 years and the areas should be sown to pasture afterwards so that any remaining seedlings are suppressed by being out-competed (Parsons and Cuthbertson 2001). However, repeated cultivation may lead to soil erosion and the breaking down of soil structure (Williamson et al. 2007).
Grazing: Grazing by goats can significantly reduce flowering and therefore restricts seed production (Parsons and Cuthbertson 2001).
Artichoke Thistle (Cynara cardunculus) flowers from November to February. Seeds can germinate at any time of the year but mostly do so after autumn rains. Seedlings grow slowly over the winter months, then grow rapidly in spring. A deep taproot develops in the first year with rosette leaves dying down over summer, to be replaced with new leaves in the plants second autumn. These new rosette leaves develop into a large 'cabbage-like' growth. Stems emerge from the crown by October and the lower leaves die off. Plants generally flower in their second summer, but can sometimes flower in their first year. The aerial growth dies after the plants have flowered in the summer, though the flower stems can remain standing for several months. The cycle begins again after autumn rains when rosette leaves develop again. Individual plants can live for many years (Parson & Cuthbertson 2001; Navie 2004).
ACT, NSW, QLD, SA, TAS, VIC, WA
Artichoke Thistle (Cynara cardunculus) is widely distributed throughout the southern and eastern parts of Australia. It is most common in Victoria and southern South Australia, with a more scattered distribution in the sub-coastal regions of New South Wales and south-east Queensland, south-west Western Australia and Tasmania (Navie 2004), with several collections from the ACT (AVH 2020).
Artichoke Thistle (Cynara cardunculus) is native to the Mediterranean region of southern Europe and northern Africa (Navie 2004).
SA, TAS, VIC
Wild Artichoke, Desert Artichoke, Spanish Artichoke, Scotch Thistle, Cardoon, Globe Artichoke.