Vaillant's fat grass is an annual plant with a sub-Atlantic distribution that extends into the western part of the Mediterranean Region, including North Africa; the species appears sporadically also along the Tyrrhenian coast of Italy, from Liguria to Lazio, Puglia, Basilicata, Sicily and Sardinia (Lampedusa). The life-cycle can be spent part in water, part on moist to dry soil. It grows on the margins of temporary pools and ponds ,on siliceous substrates, from sea level to about 500 m. This species, characteristic of the Mediterranean temporary ponds, is widespread in Sardinia, where it forms dense populations on rocky substrates with a thin layer of soil. The genus is dedicated to the French botanist Jean Baptiste Francois Bulliard (1752-1793); the species is dedicated to the Parisian botanist Sébastien Vaillant (1669-1722). Flowering period: February to May.

Italian name(s): Crassula di Vaillant (Italia), Erba grassa di Vaillant (Italia).