Herbaceous, winter annual. Prostrate growth habit with branching non-rooting stems up to 1 m in length. Pubescent trifoliate leaves, leaflets triangular to heart-shaped. Various leaf markings on upper surfaces of leaflets according to cultivar and environment; i.e. presence or absence of white, red or brown markings, solid-colored or flecked. Stipules are small and pointed, varying in hairiness and color of stripes which range from pale green to red. Calyx coloration used as diagnostic aid to identify strains and cultivars. However, anthocyanin markings are unreliable for identifying strains since they vary during the growing season. The flower head, arising from the leaf axil node, contains 3-4 flowers with a calyx and corolla. After self-fertilization, peduncles bend over and florets turn downward. Several sterile, spiny florets emerge at the end of the peduncle, enclosing 2-4 ripening seeds in the dried-out corolla and calyx. These seed burrs become buried in the upper layer of the soil during summer for subsequent germination in autumn. Strains differ in their ability to bury burrs. Burial is also affected by soil conditions, being greatest in moist, light-textured soils and least in dry, hard soil conditions. Seeds are oval, with a pronounced hilum.