Asperugo procumbens L., een ‘archaïsch’ onkruid in de duinstreek

Asperugo procumbens (Boraginaceae) has been known since the 16th century from the Netherlands. Nowadays it ranks amongst the rarest species of this country, being present at only three stable localities in the 80’s. Its former distribution pattern is rather difficult to interpret because many inland records refer to introduced specimens, including part of those from the riverine area. On account of the durability of its presence the pattern of its occurrence cannot be elucidated (fig. 2). More information is obtained from a map of records before 1850, i.e., before the ‘golden age of casuals’, which lasted from the third quarter of the 19 th to the third quarter of the 20th century. From fig. 3 it appears that the more original parts of the distribution area are the dune area (from Alkmaar to Hoek van Holland) and the lower course of the river IJssel. Presumably the plant has been conveyed by the Rhine and its branches; after having germinated on drift belts, it will have found a more durable habitat thanks to agriculture. Most records of Asperugo refer to the following types of habitat: sandy little dikes, especially along arable land, roadsides, the vicinity of farm-yards, inns and mills, and hedges. Essentially its habitat appears to be open, moderately dry, strongly influenced by some kind of manure, and provided rather regularly with moisture (Asperugo is notably sensitive to desiccation). Phytosociologically the plant is characteristic of the alliance Sisymbrion, being recorded in the Bromo-Hordeetum and the Chenopodio-Urticetum (table 1). The association Blito-Asperuginetum, named after Asperugo en Chenopodium foliosum and proposed by Westhoff & Den Held 24 cannot be asserted.