Text by Kristina Bjureke, all photos by Oddvar Pedersen. 

Wild radish, Raphanus raphanistrum ssp. raphanistrum, is an old field weed that probably came to Scandinavia in the Bronze Age or Stone Age (Hartvig 2015 about Denmark). Wild radish is annual. It grows in southern Norway, southern and central Sweden, southern Finland and Denmark.

Sea radish, R. raphanistrum ssp. landra, was first known from four old ballast and grain imports in Norway from the 19^th and 20^th century. The subspecies ssp. maritimus was introduced spontaneously with ocean currents in 2001. A comparison between the subspecies concluded that they belong to the same subspecies, and the priority name is ssp. landra. Sea radish is perennial with basic rosette leaves.

During the stormy winter of 2013/2014, new seed material arrived in Norway. The ocean currents carried seeds from seashore plants from Western Europe (The British Isles and perhaps especially the coasts around the English Channel) to our shores (Pedersen 2009, Pedersen & Grøstad 2015). Sea radish was found in over 100 localities with over 2000 individuals and has since reproduced in our region. Prior to this, it was considered an alien species that has entered the last 200 years with the help of humans (especially ballast). It is now seen as a natural species, which has spread spontaneously to our shores with the help of ocean currents (Elven et al. 2018).

The closest relative is the cultivated radish, R. sativus. The part you eat is the lower part of the stem and the upper part of the root, which is combined into one structure. The wild species can be distinguished from the cultivated R.sativus based on the thin not fleshy tap roots, yellowish-white petals, more distinct violet venation in the petals and strongly veined and clearly segmented fruits. The fruit is very special: a seed capsule that does not open. Instead, it is fragmented into small pieces, it breaks at each joint, and each segment contains a seed.

References:

Pedersen, O. 2009. Strandplanter på vandring – om nye, langdistansespredte havstrandplanter, spesielt på Lista. Blyttia 67: 75-94.

Pedersen, O. & Grøstad, T. 2015. Strandplanter på vandring – sydkysten invadert 2014. Blyttia 73: 73-85.

Hartvig, P. 2015. Atlas flora danica Gyldendal, København

Elven R, Hegre H, Solstad H, Pedersen O, Pedersen PA, Åsen PA og Vandvik V. 2018. Raphanus raphanistrum landra, vurdering av økologisk risiko. Fremmedartslista 2018. Artsdatabanken.  https://www.artsdatabanken.no/fab2018/N/1896

http://www.theplantlist.org/