greenhood, (genus Pterostylis), genus of more than 100 species of terrestrial orchids (family Orchidaceae) native to Australasia. The plants occupy a wide range of habitats, from rainforest to open grasslands. Some species are cultivated by collectors for their unusual flowers.
Greenhoods have dull-coloured hooded flowers that trap insects for pollination. The lip of the flower is hinged and seals the entrance route of an insect that enters the flower to obtain its sweet nectar. The insect must leave by means of a special tunnel through the column that is lined with hairs. Packets of pollen grains, known as pollinia, become attached to the insect as it escapes, and the pollen is thus carried to other flowers.
Some species of greenhoods are commonly known as shell orchids. The jug orchid (Pterostylis recurva) is named for its shape. The hooded orchid (P. banksii) is native to New Zealand, and the closely related king greenhood (P. baptistii) is from neighbouring Australia.