- Name also: Common Blue Sow Thistle, Blue Sow-thistle
- Family: Daisy Family – Compositae, subfamily – Cichorioideae (formerly Chicory Family – Cichoriaceae)
- Growing form: Perennial herb. Rhizome horizontal. Forms stands.
- Height: 100–150 cm (40–60 in.). Stem usually unbranched, lower part glabrous, upper part with glandular hairs. Containing latex.
- Flower: Flowers 2.5–4 cm (1–1.6 in.) wide, single flower-like capitula surrounded by involucral bracts. Capitulum’s ray-florets violet, tongue-like, 5-toothed at tip. Stamens 5. Gynoecium composed of 2 fused carpels. Involucral bracts in many rows. Capitula borne in a wide corymbose cluster.
- Leaves: Alternate, basal leaves stalked, stalk broadly winged, grooved, stem leaves amplexicaul. Blade thin, slightly hairy, with toothed margins, pinnately lobed–lobeless, terminal lobe bigger than the others, cordate–triangular, uppermost leaf-blades entire.
- Fruit: Narrowly elliptic achene, crowned by a pappus of unbranched hairs.
- Habitat: Roadsides, ditches, parks, gardens. Ornamental, sometimes left over from old gardens or an escape.
- Flowering time: July.
Blue sowthistle is native to the Ural and Caucasus mountain ranges. In Finland it is cultivated as a perennial in gardens and old manor house parks. The plant thrives in rich loamy soil so well that it needs no additional help from humans – in fact in the flower bed it is more advisable to limit its growth. As a large plant it leaves its neighbours in the shade and often spreads to form dense stands, and sometimes it escapes into the wild and spreads of its own accord.
Blue sowthistle doesn’t seem to threaten the diversity of Finland’s nature, but many other non-native plants do have the effect of threatening native plants by competing or cross-breeding with them, and even changing the qualities of their environment. Species that have spread around the world with people do not enrich our nature, but rather standardise the word’s unique communities and at worst threaten the future of Finland’s own species. Problems caused by foreign species are presently regarded as the second worst threat to natural diversity immediately behind the disappearance and change of habitats. The situation in Finland is not as bad as it is in many other parts of the world: our harsh climate, unproductive soil and ubiquitous coniferous forest don’t suit very many species. Finland’s highly fragile habitats are wetlands and broad-leaved forests, where it is wise to keep a keen eye on feral species. Their cultivation should be curbed as much as possible and if they are desired in the flower garden care should be taken that they don’t escape.