Carduus pycnocephalus L.
slender winged thistle
Annual. Stems usually branched above, (20)-60-100-(150) cm tall, with sparse multicellular hairs below, becoming cobwebby above, ribbed; wing narrowed to 1-2 mm wide between clusters of teeth; teeth 5-15 mm long, in narrowly deltoid to linear clusters; spines 3-8-(10) mm long. Lvs oblanceolate to narrowly deltoid, pinnatifid, (5)-10-30 × (2)-5-15 cm, with multicellular hairs above and cobwebby to woolly tomentum beneath; basal lvs with 3-5 pairs of lobes; lobes dentate; teeth spine-tipped; spines pale, 2-5-(8) mm long. Capitula erect to suberect, falling at fruiting, 10-20 × 5-15 mm, shortly pedunculate or subsessile in terminal clusters of 2-3-(5), also solitary, sessile, and axillary on stems; peduncles 1-2 mm diam. Involucre cylindric to obconic. Outer and middle involucral bracts narrowly lanceolate to deltoid, tapered to a subulate erecto-patent to patently curved spine, without distinct claw and limb, with glandular papillae, and cobwebby hairs at least on margins; apex green, linear; midvein raised in upper 1/2. Inner involucral bracts linear, papillate to puberulent, (1)-3-veined above; apex acute, green with scarious margins, often pink subapically. Corolla pale pinkish purple, (10)-13-15 mm long; lobes 4.5-5.5 mm long; swelling at throat of tube ellipsoid, < 2-(3) mm long. Achenes brown, ellipsoid, 3.5-4 × 1.5-2 mm; pappus 10-12 mm long.
N.: Auckland, Waikato (Ohinewai), Bay of Plenty, East Cape, Wairarapa, Wellington; S.: Nelson, Marlborough, Canterbury, Otago (Kaka Point, Otematata, Palmerston), Southland (Puysegur Point).
S. and S.E. Europe, N.W. Africa 1944
Waste land, pasture, riverbeds, roadsides, railway yards, tussock grassland.
FL Oct-Jan-(May) FT Nov-Feb-(May).
C. pycnocephalus is very similar to C. tenuiflorus and many of the characters described in Floras do not readily distinguish them in N.Z. Although many N.Z. plants can be placed with reasonable confidence in one or other sp., many populations contain a continuum of plants intermediate in the characters given. In Europe and Australia, different chromosome numbers and isozyme patterns have been reported for the 2 spp. Hybrids between them were shown to have intermediate morphology and isozyme patterns, and reduced seed-set [Olivieri, I., Amer. J. Bot. 72 : 715-718 (1985)]. Hybridism has not been investigated in N.Z.
C. pycnocephalus typically has a few capitula in a cluster at the stem apex, with 3-5 solitary sessile capitula in the axils of upper stem lvs. The involucral bracts tend to have a subulate curved erecto-patent green apex and a midvein thickened in the upper 1/2of the bract. The basal lvs generally have 3-5 pairs of leaflets and often have whitish markings along the veins and margins. The wings on the stem are slender with long spines.
