Classification
 Nomenclature
Scientific Name:
Silybum marianum (L.) Gaertn., Fruct. Sem. Pl. 2, 378 (1791)
Synonymy:
  • Carduus marianus L. (1753)
Vernacular Name(s):
Blessed thistle; Cabbage thistle; Holy thistle; Milk thistle; Our Lady's milk thistle; Variegated thistle
 Description

Annual or biennial.  Stems branched above, ridged, with sparse mealy hairs at least above, 0.5–2 m tall, not winged.  Lvs elliptic to lanceolate, lyrate-pinnatifid to pinnate, sinuate, coarsely dentate, green with conspicuous white markings along veins, (10)–20–60 × (5)–10–30 cm, with sparse short mealy hairs on lamina, and sparse long tangled multicellular hairs on midrib; base amplexicaul, auriculate, with very spinous margins;  prickles marginal, yellowish, spreading, 5–12 mm long.  Capitula ovoid, erect, 4–6 × 5–7 cm, solitary, terminal and pedunculate, and also sessile in axils of uppermost lvs; peduncles with appressed cobwebby tomentum.  Involucral bracts sparsely covered with short mealy hairs;  margins with sparse cobwebby hairs.  Outer bracts leaflike, obovate with spinous apex and margins.  Middle bracts oblong; appendage ovate, subulate, with spinous margins and a long spreading to recurved apical spine.  Inner bracts lanceolate;  appendage becoming linear-lanceolate, entire.  Corolla reddish purple, 20–28 mm long;  lobes unequal, 4–6 mm long.  Anther filaments joined at margins into a tube which encloses the basal appendages of the anthers.  Style exserted 1–2 mm beyond corolla lobes.  Achenes brown or black-streaked, obovoid, weakly transversely flattened, smooth,  c. 6 × 3 mm;  outer pappus bristles scabrid,  c. 15 mm long; inner hairs very fine.  

[From:  Webb et al. (1988) Flora of New Zealand. Volume 4.]

 Biostatus
Exotic
 Phenology

Flowering: Nov.–Jan.–(Feb.); Fruiting: Dec.–Mar.

 Bibliography
Biosecurity New Zealand 2012: Regional Pest Management Strategies Database. http://www.biosecurityperformance.maf.govt.nz/
Connor, H.E. 1977: The Poisonous Plants in New Zealand. Edition 2. Government Printer, Wellington.
Gaertner, J. 1790–1792: De Fructibus et Seminibus Plantarum. Vol. 2. Stuttgart.