Cirsium rivulare Trevors Blue Wonder - Thristle

The Cirsium rivulare 'Trevors Blue Wonder' is a river thistle with purple thistle flowers. Compared to 'Atropurupreum', which has pink-red flowers, the flower is bluish and more violet here. A superb plant for riverbanks or flowering meadows in heavy and moist to wet soil, it is also a beautiful addition to a naturalistic garden, as long as the soil is never dry. Its large pompons sway in the wind in summer and blend pleasantly with the grasses.

Cirsiums are thistles from the Asteraceae family. Cirsium rivulare is native to Switzerland and central Europe, where it grows in wet places such as meadows and mountain marshes. It is a very cold-resistant plant, adapted to damp to fresh, clayey, and fertile soils.

The cultivar 'Trevors Blue Wonder' distinguishes itself from the species by its purple colour. It is a herbaceous perennial plant with a root system whose above-ground part disappears in winter and reappears in spring. At maturity, this river thistle will form a flowering clump about 1 to 1.20 m (3 to 4ft) tall, spreading through underground stems over 50 to 60 cm (20 to 24in) wide. It develops basal leaves and fleshy, sparsely leafy stems, with long leaves sheathing the base of the stem. The foliage is dark green; the laminae are widely dissected, slightly pubescent, and edged with thorns. Flowering occurs from June to August at the ends of the stems. It takes the form of inflorescences in heads, grouped in 2 to 8 units. Each head, which can reach 3 cm (1in) in diameter, is composed of many tiny flowers, highly visited by pollinating insects. The flowering gives way to small silky fruits called achenes, which can self-sow.

The 'Trevors Blue Wonder' river thistle thrives in full sun. It prefers heavy clayey soils that are constantly moist and waterlogged even in winter. It requires at least moist soil, never dry. This tall and wild thistle adds elegance to a meadow or the edge of a pond without requiring much care. Choose typical plants for these soils to accompany it, such as waterwort, the beautiful marsh sage, and meadow rues, to name a few. Also, consider asters and poppies in moist soil. Pennisetum and the white woodrush are beautiful companion grasses. Don't hesitate to create bouquets of dried or fresh flowers; this will prevent spontaneous sowing and promote late-season flower reblooming. This variety is not invasive.