Ash trees are large trees that can reach 15 to 20 meters in height. Their branches are always opposed (one directly opposite the other). The ash leaf is usually composed of 5 to 11 leaflets of similar size, in opposite pairs with one at the tip. The fruits of the ash are called samaras or keys, elongated greenish (bean-shaped) and grouped in clusters, often abundant and sometimes persisting through the winter. The bark of a mature ash is quite thick and formed of ridges intersected by gullies in regular rhombus shapes, bringing to mind a diamond pattern.