The trunk is stout and gnarled, and can reach a metre (yard) in diameter. The bark is pale brown and thick, with cracks and vertical fissures. The leaves are pinnate and up to 20 cm (8 in) long, with twelve to twenty leaflets arranged in pairs. Each leaflet is oval with a smooth margin and yellowish green upper surface. A pair of strong, curved thorns is borne at the location of each whorl of leaves. The flowers are borne in dense axillary spikes. Each individual flower has five sepals, five petals and ten stamens. The fruits are twisted or coiled pods up to 15 cm (6 in) long, with several coffee-coloured seeds inside. P. chilensis flowers between October and December and the fruits ripen between February and April.

The trunk is stout and gnarled, and can reach a metre (yard) in diameter. The bark is pale brown and thick, with cracks and vertical fissures. The leaves are pinnate and up to 20 cm (8 in) long, with twelve to twenty leaflets arranged in pairs. Each leaflet is oval with a smooth margin and yellowish green upper surface. A pair of strong, curved thorns is borne at the location of each whorl of leaves. The flowers are borne in dense axillary spikes. Each individual flower has five sepals, five petals and ten stamens. The fruits are twisted or coiled pods up to 15 cm (6 in) long, with several coffee-coloured seeds inside. P. chilensis flowers between October and December and the fruits ripen between February and April.