Raphanus raphanistrum subsp.
raphanistrum L., Wild Radish
Account Summary
Introduction, archaeophyte, a rare or very rare casual weed of cultivation.
1900; Praeger, R.Ll.; Florencecourt.
July to October.
Growth form and preferred habitats
This weedy annual form of the Wild Radish is not at all common in the north of Ireland and it never has been. The cultivated Garden Radish is a completely different species (R. sativus L.), but another form of the current species, common in particular on Irish Sea coasts, is subsp. maritimus (Sm.) Thell. (Sea Radish). The latter is a robust biennial as opposed to this annual form. Fruit characters clearly distinguish the subspecies (Stace 1997).
While the flower colour of Wild Radish can vary from white to pale yellow or pale lilac (rarer), the petals often being conspicuously veined dark violet beneath (Hackney et al. 1992), the fruit is much more clearly distinctive. It has a long, tapering, persistent beak and, when mature, the pod develops distinct but not very deep constrictions between the bead-like seeds (Clapham et al. 1962; Webb et al. 1996). In April and May, when not yet in flower, the rough bristly hairiness of the plant makes it easily mistaken for the extremely variable Sinapis arvensis (Charlock). When flowering from June to September, the two can be distinguished by the deeper yellow petals of Charlock and by the orientation of the sepals: erect in Wild Radish, spreading widely in Charlock. Undoubtedly, however, the mature fruit of R. raphanistrum is its most distinctive feature: the brown pods develop bead-like swellings separated by internal cross-walls and they break between the 1- or 2-seeded beads, unlike most crucifer pods which split downwards along their length (Rich 1991). Subsequently, the segments of the broken pods gradually decompose with age to release the seeds.
Wild Radish appears to prefer disturbed, moderately fertile, fairly dry, sunny soils on waysides, gardens and waste ground, including around docks (Sinker et al. 1985; Rich 1991). Previously, however, before the major switch in Irish land use towards pastures and meadows in the 1950s, Wild Radish was quite a common noxious weed colonising arable fields and their margins, especially those with sandy or peaty-loam, mildly acid soils.
Fermanagh occurrence
In Fermanagh, over the years, subsp. raphanistrum has only been recorded a total of nine times, six of the records belonging to the post-1975 period. Locally, therefore, it is a rare or very rare casual annual weed and is very thinly and widely scattered.
Additional to the first record given above, the details of the other eight are: field at Cranbrooke, Colebrooke estate, near Fivemiletown, 1946, MCM & D; sandy fields below Gortaree, Slieve Rushen, 1949, MCM & D; waste ground behind St Michael's Church, Enniskillen, September 1986, RHN; Derrychara, Enniskillen, 29 July 1987, RHN: four plants still there 16 July 2010, RHN; Tempo, 31 July 1987, RHN; Belleek village, 1 August 1987, RHN & RSF; roadside at Mullaghmore Bridge, NW of Ederny, 19 October 1996, RHN.
British and Irish occurrence
This noxious weed is still quite common, although often merely casual, throughout all latitudes in Britain and especially frequent south of a line between Hull and Liverpool (New Atlas). In the Flora of NE Ireland, 2nd edition, Praeger (ever the optimist) went so far as to describe the occurrence of subsp. raphanistrum in the three NE counties as being, "not rare". In 1938, Praeger may have been recollecting times when the plant previously was a common weed of arable cultivation and indeed 'not rare' to Irish naturalists of his generation.
The plant appears to have spread as a seed contaminant of grain and in Ireland was most frequent in the S and E of the island. The Cen Cat Fl Ir 2, for instance, lists Wild Radish from 37 of the 40 VCs on the island, the exceptions being S Tipperary, SE Galway and Roscommon (H7, H15 & H25).
With the advent of much improved, scientific seed cleaning in the 1940s and especially following the development of selective herbicides during the last 50 years, Wild Radish is now easily controlled and subsp. raphanistrum has significantly declined, both as an agricultural weed and in the wider countryside. The New Atlas map shows that although there has been a major decline in Wild Radish across both B & I (a Change Index of -1.39), it is certainly not on the verge of extinction in Ireland as was imagined or predicted in Flora of Connemara and the Burren. Indeed Reynolds (2002) in A Catalogue of Alien Plants in Ireland declared the plant, "fairly common".
European and world occurrence
While Clapham et al. (1962) considered R. raphanistrum as "doubtfully native" in the flora of B & I, it is now recognised as an archaeophyte which almost certainly originated in the Mediterranean basin. It spread widely from there among agricultural seed and possibly the young plant was also used as an edible pot herb, as well as in herbal medicine. It has been spread throughout Europe and N Africa, although rarer towards the east and throughout Asia. It was also carried by man in the same way almost world wide, to N & S America, the Cape of Africa, Australia and New Zealand. It has even been transported to E Greenland and to numerous remote oceanic islands, eg Kerguelen in the South Indian Ocean (Hultén & Fries 1986, Map 996).
Threats
None.