These days, the marsh gentian is relatively rare in the Netherlands.
This is due to the disappearance of wet heaths and the encroachment of grasses. Thanks to the park's long-term policy of protecting its wet heaths, this plant is flourishing in the Deelensche Veld.
The marsh gentian is a perennial that blooms in late summer and can grow up to 60 cm high. It blooms between mid-July and late August, but some plants can start much earlier. The plants can live for up to 30 years. The flowers are dark blue and the leaves are dark green and elongated to linear in shape.
The marsh gentian is the only host plant for the rare alcon blue butterfly. They lay their eggs on the calyx and corolla of the marsh gentian, which later provides food for the caterpillars.