Bouteloua gracilis - Boutélou gracieux, Grama bleu

Bouteloua gracilis, the blue grama, is a small perennial grass recognisable by its astonishing horizontal, comb-like spikes. They seem to float above a low clump of fine, grey-green to bluish leaves. Initially tinted green and purple, they turn brown as they dry and remain decorative in autumn. This botanical species tolerates dry summers, cold and poor soils. Its compact habit makes it suitable for a rock garden, a gravel border or a small, lightly watered meadow.

Bouteloua gracilis belongs to the Poaceae family. It is a warm-season grass: its growth starts fairly late in spring, once the soil has warmed up, then accelerates during summer. Its above-ground parts dry out in autumn and its rootstock remains dormant through winter. The species is native to a large part of North America, from the western and central provinces of Canada down to Mexico. It dominates certain short-grass prairies of the Great Plains and also grows on rocky hillsides, sandy soils, dry clearings and plateaus subject to wide temperature fluctuations. Blue grama forms a dense clump 30 cm wide, from short scaly rootstocks. In a dry garden, the clump spreads slowly. In cooler conditions or with regular watering, it may eventually form a dense carpet. Its fibrous, highly branched root system enables it to make rapid use of any rainfall and endure long periods without water. The foliage reaches 20 to 30 cm in height. It consists of narrow, somewhat stiff leaves, ranging in colour from light green to blue-green. In autumn, they take on golden tones, sometimes mixed with orange or reddish brown, before drying to a straw-beige colour. From August to October, slender stems bear one to three spikes 4 to 6 cm long. Each spike holds its flowers on one side of its axis only, giving it the appearance of a small brush set horizontally. The spikes are green when they first appear, then take on purplish pink and brown tints. Their unusual shape is the origin of the English name "mosquito grass": seen from a distance, they resemble small hovering insects. The inflorescences can be cut and dried for cut flower arrangements. Very hardy, this grass tolerates temperatures close to -25 °C in well-drained soil. It grows in sand, gravel, chalky soils and even clay, provided water drains away quickly. Persistent winter damp is more harmful to it than cold. It can self-seed in gravel or on bare soil.

You can plant Bouteloua gracilis in small groups in a sunny rock garden, on a dry bank, along a gravel path or in a low meadow. This grass pairs well with Asclepias tuberosa, with its orange flowers, Aster 'October Skies', a deep blue, and Artemisia alba 'Canescens', with its silver foliage. All these plants enjoy full sun and poor soils that dry out in summer. Planted in quantity and mown occasionally, blue grama can also form a hardy lawn in lightly trafficked parts of the garden, but it starts into growth late in spring and dries out in winter.