On several places in pastures in the municipality of Wymbritseradeel (prov. Friesland) occur crocuses that are naturalized there since 50 years or longer. The author supposes that they have been introduced there with earth from dug off terps used for improvement of the soil. The crocuses belong to C. tomasinianus Herb. and C. vernus (L.) Hill, whereas intermediates between these two species also occur.