Lichenomphalia umbellifera, also known as the lichen agaric or the green-pea mushroom lichen, is a species of basidiolichen in the family Hygrophoraceae. It forms a symbiotic relationship with unicellular algae in the genus Coccomyxa.
The species was first described by Carl Linnaeus in 1753 as Agaricus umbelliferus. It was transferred to Lichenomphalia in 2002.
L. umbellifera has a wide geographic range and displays a considerable amount of phenotypic plasticity, but phylogenetic research has confirmed that these populations represent a single species. Two related taxa have been described in the genus Lichenomphalia, but are yet unnamed.
The mushroom is white to yellowish-tan and hygrophanous, and occurs throughout most of the year on damp soil and rotting wood. Its cap grows up to 3 cm wide. Its stalk is 1âÂÂ3 cm tall and 1âÂÂ3 mm wide. The spores are white or yellowish, producing a white spore print.
It is regarded as nonpoisonous but its small size incites little culinary interest.
L. grisella is uncommon and has a brown cap.
Other similar species include Chromosera cyanophylla, Chrysomphalina aurantiaca, Chrysomphalina chrysophylla, Contumyces rosellus, and Rickenella fibula.
It can be found in the Northern Hemisphere, particularly in the region of the Arctic. In the North American Pacific Northwest, it is common and can be found northward from Santa Cruz.