Van Gogh saw the work of the impressionists for the first time when he arrived in Paris in February 1886. He realized that his own palette was dark and old-fashioned and began experimenting with lighter colours and a different kind of brushstroke. In the spring and summer of the following year he regularly went painting in the open air in Asnières, a village near Paris. Later, in a letter to his sister Willemien, he wrote that in the landscape there he ‘[saw] more colour than before’. This patch of grass may well have been painted in Asnières. He probably wanted to practice his new technique. Every brushstroke coincides precisely with what he is depicting: the blade of grass, the petal or the stem.
For this work Van Gogh used a canvas he had already painted on previously. X-ray images reveal the head of a woman with a hat under Patch of grass. It is assumed that he painted this female head in 1884-1885 in the Brabant village of Nuenen, so about two and a half years before he painted Patch of grass on top of it. The huge contrast between his sombre use of colour in his Nuenen period and his colourful and light palette in Paris is striking. His extremely rapid and radical development in style is thus literally embodied in this single painting.