Cirsium arvense
Environmental Weed (2024)
Common names
Californian thistle
Biostatus
Exotic
Category
Vascular
Structural class
Herbs - Dicotyledonous composites
Flower colours
Red/Pink, Violet/Purple
Detailed description
Rhizomatous perennial often forming large patches. Stems branched above; fine cobwebby hairs below, becoming glabrous above, (20)-40-100-(150)cm tall, ribbed, not winged or sometimes with a spiny wing 0-1-(2) cm long decurrent from leaf bases. Leaves lanceolate, pinnatifid, green above, pale beneath, (2)-4-15 x 1-5cm, glabrous or with cobwebby hairs; lobes deltoid to lancolate; prickles pale, 5-10mm long. Capitula narrowly ovoid to cylindric at flowering, erect, 1.5-2-(2.5) X 0.7-1.5-(2) cm in cymes or cymose panicles; peduncles 5-40 mm long. Outer involucral racts linear, ciliate; apex acute, not spinous, erect. Corolla usually pale purple or mauve, sometimes white, 12-18mm long; lobes c. 3mm long. Style slightly exerted beyond carolla lobes. Achenes pale, cylindric, 3-4 X 1-1.5 mm; pappus 20-25 mm long, shorter in male; cilua on pappus bristles 2-3 mm long. (Webb et al., 1988).
Habitat
Terrestrial.
Conservation status
Not applicable
Detailed taxonomy
Family
Ecology
Flowering
December, January, February
Fruiting
December-April
Year naturalised
1878
Origin
Eurasia
Reason for introduction
Accidental
Life cycle and dispersal
Rhizomartous, perennial. (Webb et al., 1988). Almost completely dioecious: female plants do not produce viable pollen but male plants occasionally set a few seeds (Webb et al., 1988).
Wetland plant indicator status rating
Information derived from the revised national wetland plant list prepared to assist councils in delineating and monitoring wetlands (Clarkson et al., 2021 Manaaki Whenua – Landcare Research Contract Report LC3975 for Hawke’s Bay Regional Council). The national plant list categorises plants by the extent to which they are found in wetlands and not ‘drylands’. The indicator status ratings are OBL (obligate wetland), FACW (facultative wetland), FAC (facultative), FACU (facultative upland), and UPL (obligate upland). If you have suggestions for the Wetland Indicator Status Rating, please contact: [Enable JavaScript to view protected content]
FACU: Facultative Upland
Occasionally is a hydrophyte but usually occurs in uplands (non-wetlands).
Other information
Etymology
cirsium: A kind of thistle
arvense: Growing in arable fields
Environmental Weed (2024)
This plant is named in a list of 386 environmental weeds in New Zealand 2024 prepared by DOC. 759 candidate species were considered for inclusion on this new comprehensive list of environmental weeds in New Zealand. The species considered were drawn from published lists of weed species, lists of plants that must be reported or managed by law if observed, existing national and regional programmes and agreements for pest management, and species already managed by the Department of Conservation (DOC). Candidate species were then assessed to see if they were fully naturalised and whether they have more than minor impacts in natural ecosystems. Read the full report here.
NVS code
The National Vegetation Survey (NVS) Databank is a physical archive and electronic databank containing records of over 94,000 vegetation survey plots - including data from over 19,000 permanent plots. NVS maintains a standard set of species code abbreviations that correspond to standard scientific plant names from the Ngä Tipu o Aotearoa - New Zealand Plants database.
CIRARV