The Texas lignumvitae (Guaiacum angustifolium) belongs to Zygophyllaceae (the Caltrop family). It is a small evergreen tree that is distributed from central and southern Texas in the United States to northeastern Mexico. This tree grows in the bushes of valleys and canyons and is about 6 m high. The branches are short and curved, making it a compact canopy. The leaves are scaly, pinnate compound, opposite or crowding. The long peduncles grow from the axils and bloom sky blue or purple flowers from spring to summer. The fruits are flat, heart-shaped, with seeds usually wrapped in two bright red arils.