The identifications and distribution data presented here are based on herbarium records held at the Florence (FI), Rome (RO), and Padua (PAD) herbaria, supplemented by GBIF occurrence data and published regional floras. Field conditions vary; identifications should be confirmed against multiple characters.
The Genus Cirsium in Italy
Cirsium Mill. (tribe Cardueae, family Asteraceae) is the largest thistle genus in the Italian flora, with approximately 30 species and subspecies recorded across the peninsula, the large islands, and the Alpine massif. The genus is distinguishable from the closely related Carduus by its feathery (plumose) pappus bristles — a character visible to the naked eye on mature achenes — compared to the simple (non-plumose) pappus bristles of Carduus. Onopordum is further separated by its larger stature, densely tomentose white stem wings, and markedly larger flower heads.
In Italian grasslands, Cirsium species occupy a broad range of niches from wet alluvial meadows along the Po tributaries to dry calcareous slopes in Calabria and the Sicilian interior. Altitude records extend from sea level on the Adriatic coast to 2,400 m in the Gran Paradiso and Stelvio national parks.
Key to the Principal Grassland Species
The following character set covers the eight Cirsium taxa most frequently encountered in non-wooded habitats below 2,000 m. For montane specialists and rare endemics, consult the regional flora references listed at the end of this article.
Primary Separation Characters
Two characters divide the common Italian Cirsium most efficiently in the field:
- Leaf indumentum on the upper surface: glabrous or sparsely hairy above → proceed to group A; densely white-felted above → proceed to group B.
- Stem winged or unwinged: distinct spiny wings running continuously down the stem → Carduus (not Cirsium); interrupted or absent wings → continue within Cirsium.
Group A — Upper Leaf Surface Green, Glabrous to Sparsely Hairy
Cirsium vulgare (Savi) Ten. — Spear Thistle. Biennial, 60–150 cm. Leaves deeply pinnately lobed, upper surface with scattered stiff bristles, lower surface grey-felted. Phyllaries with long spiny tips. Flower heads 3–5 cm, solitary or in groups of 2–5. Purple-red florets. Pappus to 3 cm. Distribution: throughout Italy, all altitudinal zones; commonest thistle of disturbed ground and nutrient-enriched grassland. Bloom: June–September.
Cirsium arvense (L.) Scop. — Creeping Thistle. Perennial, 30–120 cm, spreading by horizontal roots. Leaves variable, shallowly to deeply lobed, weakly spiny. Dioecious or functionally so; flower heads small (1–2 cm), pink-purple, numerous in a terminal corymb. A major weed of arable margins and disturbed pasture throughout the peninsula and islands. Bloom: July–September.
Cirsium palustre (L.) Scop. — Marsh Thistle. Biennial, 50–200 cm. Continuous spiny wings on stem; leaves narrow, deeply lobed, dark green above, pale below. Small purple heads (1.5–2.5 cm) in dense terminal clusters. Wet meadows, marshes, river margins from sea level to 1,800 m. Bloom: June–August.
Group B — Upper Leaf Surface Distinctly White-Felted
Cirsium eriophorum (L.) Scop. — Woolly Thistle. Biennial, 80–200 cm. Stem not winged or very narrowly so. Phyllaries densely white-woolly, the outer ones reflexed. Flower heads very large (4–7 cm), solitary. Calcareous grasslands and rocky slopes, Pre-Alps and Apennines, 400–1,800 m. Bloom: August–September.
Cirsium italicum (Savi) DC. — Italian Thistle. Perennial, 60–130 cm. Stem with continuous white-cottony wings. Leaves broadly lobed, upper surface grey-green, lower surface white-felted. Heads 2–3.5 cm, pale pink to lilac, in terminal clusters. Mesic meadows and forest clearings, central and southern Apennines and some Adriatic coastal areas, below 1,200 m. Near Threatened at national level; habitat loss through scrub encroachment is the primary pressure. Bloom: June–August.
Habitat Associations and Ecological Notes
Italian grassland Cirsium species broadly partition into three habitat guilds, though overlaps are frequent at transitional sites:
Dry Calcareous Grasslands (Festuco-Brometea)
These well-drained, often south-facing slopes on limestone and dolomite support the densest thistle diversity. C. eriophorum is the characteristic tall species; C. acaule (stemless thistle) forms low rosettes in grazed short turf. Species richness peaks in the Pre-Alpine foothills between 600 and 1,200 m, where the mosaic of mown hay meadow, ungrazed rough grassland, and scrub margins provides heterogeneous conditions within small areas.
Mesic Lowland Meadows (Molinio-Arrhenatheretea)
C. vulgare and C. arvense dominate this habitat group in northern Italy, particularly in fields with elevated nitrogen from livestock. C. italicum reaches its northern limit in the lower Apennine foothills of Emilia-Romagna, typically in meadows cut once per year in late summer. Traditional hay-cutting regimes that leave late-summer flowering thistles are strongly associated with higher Cirsium diversity in surveys conducted between 2015 and 2022 by the Italian Botanical Society.
Montane and Subalpine Meadows (Nardion, Caricion ferrugineae)
Above 1,600 m, C. spinosissimum (yellow thistle) becomes the characteristic Cirsium of alpine pastures. This species forms dense spiny rosettes and is tolerant of heavy cattle grazing — a trait that makes it an indicator of overgrazed alpine turf. C. montanum (= C. monspessulanum subsp. ferox) is documented from the Monte Baldo range in Trentino, where it occupies south-facing scree edges and limestone pavement edges between 800 and 1,600 m.
Field Identification Challenges
Several Cirsium species in Italy produce natural hybrids where their ranges overlap. The cross C. vulgare × C. arvense is occasionally recorded in disturbed pastures and can cause confusion due to intermediate leaf shape and smaller-than-usual flower heads on an erect biennial-type plant. Hybrid plants are usually partially or wholly sterile, producing malformed or abortive achenes — a useful additional check.
The distinction between C. italicum and C. vulgare is most reliably made on phyllary characters: in C. italicum the middle and outer phyllaries widen into a short oval blade at the tip before the terminal spine, giving a distinctive spoon-shaped outline, while in C. vulgare the phyllaries taper gradually into the long terminal spine without this widening.
Recommended References
For definitive identification and full synonymy, the following sources cover Italian Cirsium in detail:
- Pignone, D. & Garbari, F. (2010). Flora d'Italia, vol. 3. Edagricole, Bologna.
- Tutin, T.G. et al. (eds.) (1976). Flora Europaea, vol. 4. Cambridge University Press. Available via Plants of the World Online.
- GBIF occurrence records for Italy: Cirsium on GBIF.
- IUCN Red List — Italian national assessments: iucnredlist.org.