S. nux-vomica is a medium-sized tree with a short thick trunk. The wood is dense, hard white, and close-grained. The branches are irregular and are covered with a smooth ashen bark. The young shoots are a deep green colour with a shiny coat. The leaves have an opposite decussate arrangement, short stalked, are oval shaped, also have a shiny coat and are smooth on both sides. The leaves are about 4 inches (10 cm) long and 3 inches (7.6 cm) wide. The flowers are small with a pale green colour with a funnel shape. They bloom in the cold season and have a foul smell. The fruit are about the size of a large apple with a smooth and hard shell which when ripened is a mild shade orange colour. The flesh of the fruit is soft and white with a jelly-like pulp containing five seeds covered with a soft woolly substance. The seeds are removed from the fruit when ripe. They are then cleaned, dried and sorted.
The seeds have the shape of a flattened disk completely covered with hairs radiating from the center of the sides. This gives the seeds a very characteristic sheen. The seeds are very hard, with a dark grey horny endosperm where the small embryo is housed that gives off no odour but possesses a very bitter taste.