Lathraea clandestina

Orobanchaceae. Parasitic perennial native to Western Europe, mainly found in France, Northern Spain, Belgium, and Italy. It grows in cool, shaded undergrowth, along the banks of streams and rivers, where it parasitizes the roots of willows, poplars, alders, and hazels, from the plains up to about 1,000 meters.

Entirely devoid of chlorophyll, it has neither leafy stems nor visible green leaves: its entire vegetative life takes place underground, through a network of whitish rhizomes bearing fleshy scales. Only the flowers emerge from the ground at flowering time, appearing directly between dead leaves and mosses as if by magic.

These flowers, of an intense and bright purple-violet, are bilabiate, tubular, grouped in dense clusters close to the ground. They barely reach 5 to 8 cm in height. In its natural habitat, its flowering extends from March to May, depending on altitude and exposure.

Long considered uncultivable, it has nevertheless been successfully established in several European botanical gardens, notably in the United Kingdom where the RHS Garden at Wisley provides a notable example. The key lies in the direct contact of rhizome fragments with the roots of a compatible host — willow, alder, poplar, or hazel — in constantly moist and deeply shaded soil. The establishment is random and may take one to two seasons, but once parasitism is established, the plant maintains itself and spreads spontaneously from year to year. Its Latin epithet, clandestina, says it all about its character: it acts at will, invisible, and reveals itself only in spring.