- Family: Daisy Family – Compositae, subfamily Carduoideae
(formerly Aster Family – Asteraceae)
- Growing form: Perennial herb. Rootstock strong.
- Height: 30–80 cm (12–32 in.). Stem erect, branchless–top sparsely branched, underside of capitulum thick, sparsely short-haired, slightly rough.
- Flower: Single flower-like 3–4.5 cm (1.2–1.8 in.) capitula surrounded by involucral bracts. Capitula flowers purplish, ray-florets neuter, obliquely funnel-shaped, tip lobed; disc florets tubular. Stamens 5. Pistil of 2 fused carpels. Involucre barrel-shaped, involucral bracts overlapping in many rows, basal part green, appendage dark brown–black, roundish or long, ciliately fringed, thread-like tip often descending oblique. Capitula usually solitary, terminating stem branches.
- Leaves: Alternate, short-stalked. Blade broadly lanceolate–lanceolate, with regularly toothed margin, not lobed.
- Fruit: Flattish, yellowish white, 3–4 mm (0.12–0.16 in.) long achene, tip with short bristles.
- Habitat: Meadows, field margins, banks, forest margins, open broad-leaved woods.
- Flowering time: July–August.
Wig knapweed has arrived in Finland from the east, and its habitats are linked to traditional methods of agriculture. Häme and especially Savo–Karelia have been the core of slash-and-burn agriculture in Finland, and wig knapweed is often found there on banks and dry meadows. It also perseveres in the margins of forest clearings and in light-filled broad-leaved forests. The last burn-beaten areas are beginning to close up, and this is reflected in the way that the species is becoming rarer. Its habitat stretches from eastern Europe to western Siberia and it would appear to favour a continental climate, or to avoid coastal climates, whichever way you look at it. Knapweeds have been popular in gardens throughout the ages as ornamentals in sunny and perhaps slightly dryish areas. Although many exotic species are grown as perennials, wig knapweed and other domestic species deserve more attention than they currently receive as wonderful plants in flowering meadows.
Three purple-flowered knapweeds have established themselves in Finland, and these are most easily differentiated from each other by the appearance of the appendage on the tip of the capitula’s involucral bracts. Greater knapweed (C. scabiosa) is easy to tell apart because of its lobed leaves. The appendages on wig knapweed’s involucral bracts are usually black and ciliately fringed while brown knapweed’s (C. jacea) are brown with membranous, ragged margins. The species favour the same kinds of open, quite rich and dry habitats, but they are not often found growing together because brown knapweed grows mainly in the west and especially the south-west. Wherever brown knapweed thrives, wig knapweed is quite scarce, and it is completely absent in wide areas. Lesser knapweed (C. nigra), which can be found occasionally in Finland, has the same kind of appendage as wig knapweed but its capitula do not have any large funnel-shaped ray-florets.