Silphium laciniatum

Silphium laciniatum, better known as compass plant, is a towering perennial, with daisy-like, dark-centred flowers that reach up to 3 metres (10 feet). It is called the compass plant because of its leaves' ability to orient themselves on a North-South axis based on the rising sun. The stems exude a highly aromatic resinous sap reminiscent of turpentine. It thrives in full sun, in moist and rich, even heavy and chalky soil. A true icon of the wet and fertile prairies of North America, it can live for a hundred years. Its sculptural and sun-like silhouette is impressive on the horizon, adorned with insects and birds, at the edges of wild gardens.

Belonging to the large Asteraceae family, Silphium laciniatum is a cousin of Helianthus and Heliopsis, native to the wild prairies of Ontario, Canada, the eastern and central-western United States, as far as New Mexico. It is a herbaceous perennial that forms a huge rosette at ground level, from which branching stems emerge in summer, bearing few leaves and crowned with large golden-yellow flowers. In good growing conditions, this plant can easily reach 3 metres (10 feet) high and 70 cm (28in) wide. Each plant can produce up to 12 rough and aromatic stems, carrying leaves of quite varied shapes and sizes. They measure from 4 to 60 cm (2 to 24in) long, some reaching 30 cm (12in) wide. They are hairy, smooth or toothed, sometimes petiolate and bright green. Juvenile leaves emerge in random positions. In two or three weeks, their petioles orient themselves so that they position themselves vertically, towards the right or left. The resulting dual orientation, East-West and North-South, reduces the amount of sunlight reaching the leaf surface, therefore optimizing water use in the leaf tissues. The nectar-rich flower head is about 8 cm (3in) in diameter, composed of 27 to 38 ligulate golden-yellow flowers from July to October. The almost 2 cm (1in) seed is loved by by birds. The lifespan of this silphium is impressive, with some estimated to be a hundred years old.

Planting Silphium laciniatum is an investment for the future in garden design. It belongs in a shrub border, in a wild bed, in the background or at the edges of the garden, in a very open position. This plant is also a good plant for bordering ponds with its architectural silhouette and abundant foliage, with tall or medium-sized grasses, Artemisia lactiflora, 'herbstchnee' or laevis asters, and giant scabious Cephalaria gigantea.

North American settlers supposedly used the leaves of this Silphium to navigate when the sky was cloudy. It is also a medicinal and aromatic plant, used by Native Americans and settlers. Today, it is endangered in its country of origin due to the slow degradation of its natural habitat.