Lathraea L. is a small genus of five to seven species of holoparasitic flowering plants in the family Orobanchaceae, order Lamiales. The plants are entirely devoid of chlorophyll and cannot photosynthesize; instead, they obtain all water and nutrients by parasitizing the roots of nearby host trees and shrubs using specialized root structures called haustoria.
The genus has a native range spanning temperate Europe and Asia. Most species are rarely visible above ground outside of their brief flowering season — a trait reflected in the genus name, derived from the ancient Greek λαθραῖος (lathraîos), meaning "clandestine." The majority of each plant consists of a branched, whitish underground stem densely covered with thick, fleshy, colourless scale leaves.
The best-known member is the common toothwort (Lathraea squamaria), which parasitizes hazel, alder, and occasionally beech, appearing in shady hedgerows and woodland margins across Europe. It is also considered protocarnivorous: its underground scale leaves form hollow chambers lined with stalked glandular hairs capable of trapping and digesting insects, providing the plant with an additional nitrogen source. Purple toothwort (Lathraea clandestina) is native to western France, Belgium, northern Spain, and locally central Italy, where it parasitizes alder, poplar, and willow, producing striking dark-purple flowers directly at soil level. The Rhodope toothwort (Lathraea rhodopaea) is found in the Rhodope Mountains and Rila range of southeastern Europe.
Lathraea was described by Linnaeus in Species Plantarum (1753) and is now placed in the largely parasitic family Orobanchaceae following molecular phylogenetic studies that united it with the broomrapes.
Etymology
The genus name Lathraea is derived from the ancient Greek λαθραῖος (lathraîos), meaning "clandestine" or "hidden." The name alludes to the plant's habit of remaining invisible underground for most of the year, only emerging briefly at the soil surface when in flower.
Distribution
Lathraea species are native to temperate Europe and Asia. L. squamaria is the most widespread, occurring across much of Europe. L. clandestina is native to western Belgium, western and central France, northern Spain, and locally central Italy, and has become naturalized in parts of the British Isles. L. rhodopaea is concentrated in the Rhodope Mountains and Rila range of southeastern Europe.
Ecology
All Lathraea species are obligate root holoparasites, attaching to host root systems via haustoria and lacking any photosynthetic capacity. Host preferences vary by species: L. squamaria favours hazel, alder, and beech in shaded habitats; L. clandestina primarily parasitizes alder, poplar, and willow. L. squamaria is additionally considered protocarnivorous — its underground scale leaves form enclosed chambers lined with glandular hairs that trap and digest small invertebrates, supplementing nutrient uptake from the host.
Taxonomy Notes
Lathraea was described by Linnaeus in Species Plantarum (1753, vol. 2: 605). It is placed in the family Orobanchaceae (order Lamiales), a broadly parasitic family that molecular phylogenetics has shown to include former Scrophulariaceae members. GBIF recognizes 15 descendant taxa under the backbone entry for Lathraea L.
