Salvia uliginosa

Unlike most other species of sage, the Salvia uliginosa, also known as Bog Sage, is a perennial plant that thrives in moist to wet soils. This vigorous but moderately hardy plant can reach a height of up to 2m (7ft) and offers a spectacular and poetic flowering display towards the end of the season, with upright spikes adorned with sky-blue flowers. Sometimes slow to establish, it spreads through stolons and can eventually cover large areas where it is happy. To give it the best chance against winter harshness, it should be planted in spring, in a very sunny location, in fresh, slightly alkaline soil.

Bog Sage is a perennial herb with deciduous foliage that belongs to the Lamiaceae family. It is originally from South America and thrives in open and marshy areas. It grows very quickly, typically reaching a height of 1.50m (5ft) and spreading up to 80cm (32in) to 1m (3ft). Bog Sage has a rhizomatous growth habit, with stems borne by an underground stoloniferous stem that can extend deep. The plant features light foliage carried by thin stems, which are narrow, square in cross-section, and bear mostly opposite leaves, separated along the stem by long internodes. The leaves are narrow, measuring 5 to 13cm (2 to 5in) in length and 1 to 2cm (1in) in width. Their surface is slightly hairy or glabrous, and their margin is dentate. The stems branch out and produce numerous floral spikes that succeed each other from June to November. The small flowers are tubular and bilabiate, measuring 1.5 to 2cm (1in) in length, and have two lips with the upper lip shaped like a helmet. They are a vivid azure blue, marked with a small white throat that attracts attention as well as pollinating insects. The peacock butterfly is often seen feeding on them and gathering strength before winter. Vegetation restarts at the end of May.

Bog Sage has a spectacular and long-lasting flowering display but can also be demanding. It is often used in dahlia beds, which lightens the overall floral display and enhances the colours of other plants. Sage enthusiasts can combine it with other plants like Euryops, bright pink Salvia greigii, vivid red Salvia darcyi, or yellow-flowered Salvia glutinosa. It can also be combined with Heleniums or pure white Ethiopian arums and yellow irises on the banks of a pond. Bog Sage is a "cloud" plant that enhances colours and allows many combinations.

The Salvia genus is the most diverse in the Lamiaceae family, with over 900 species of annuals, perennials, and soft-wooded shrubs distributed worldwide, except in very cold regions and tropical forests.