Eryngium vesiculosum

Prostrate perennial (sometimes annual or biennial) herb, with short rootstock and clusters of blackish tubers. Basal leaves somewhat rigid, lanceolate, blades 2–15 cm long with long spinous teeth, petiole c. equal to blade. Flowering heads ovoid or hemispheric, 5–7 mm long, 6–8 mm wide on peduncles 1–3 cm long, arising directly from rosette and from one axil of successive pairs of opposite spiny bracts on trailing branches to 30 cm long; bracteoles of involucre 12–13 mm long, longer in primary heads; petals at first white, becoming bluish, apically bifid or sometimes appearing laciniate. Fruit (including persistent calyx segments) 3–4 mm long, covered with shortly acuminate vesicular scales Flowers Dec.–Feb.