Hierochloe odorata

The Hierochloe odorata, also known as sweet grass, bison grass, or sweet hay, is a modest-looking grass that would not have much interest if it were not for its powerful vanilla scent that it emits when it is in a warm situation or when its leaves are crushed. A scent that can also be found in dried leaves, sometimes used to scent linen in the form of braids. It is a trailing species, very resistant to cold, adapted to non-calcareous marshy areas. The best way to cultivate it is in a well-exposed pot, in a suitable substrate, to fully enjoy its pleasant vanilla scent.

The Hierochloe odorata belongs to the large family of grasses. It is a species found in almost the entire northern hemisphere, from Europe to Asia and passing through America. In its natural state, it can be found, for example, in the meadows of one of the last primary forests in Europe, the Białowieża Forest located in the east of the continent. A preserved place where the last European bison still graze. It is a plant that is also quite widely cultivated for its fragrant principle.

Sweet grass is a perennial grass with trailing underground rhizomes, although less invasive than our couch grass. Its vegetation is deciduous: in spring, bright green foliage emerges from the ground, composed of fine, flexible linear leaves. The whole forms tufts of 60 to 70 cm (24 to 28in) in height when flowering. In open ground, the plant can cover 1 m² in one year under good conditions. The leaves contain a highly fragrant molecule called coumarin, whose scent is similar to vanilla. They are used in aromatherapy and to flavor certain spirits. The flowering, also modest-looking, takes place in June-July. From the foliage emerge small whitish to greenish flower spikes.

This little fragrant grass was once used to scent churches, and nowadays, in the USA, it is still highly prized for cultivation in pots and hanging baskets alongside flowering plants, placed near the house to enjoy its pleasant scent. In this case, a peat-based soil without fertiliser is used, and watering is done with rainwater or non-calcareous tap water. If you have created a peat bog or a basin with clayey and acidic soil in your garden, you can plant bison grass on its banks, at a very shallow depth. It thrives in full sun or partial shade, in acidic, nitrogen-poor, peaty or humiferous soil that remains moist to wet.