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Oenothera glazioviana P. Micheli, Large-flowered Evening-primrose

Account Summary

Introduction, neophyte, a rare garden escape.

July 1982; Northridge, R.H.; roadside waste ground on the Tempo road near Enniskillen.

Oenothera is a large, originally American genus of mainly annuals and biennials, (rarely perennial) many of them taxonomically complex and critical, the species limits being still a matter of opinion amongst taxonomists (Stace 1997; Stace & Crawley 2015). Some species have large, spectacular, yellow flowers, making them popular with gardeners. At least four species of Evening-Primrose (so called because of their evening-opening primrose-yellow petals), plus several hybrids, have 'jumped the garden wall' and become quite commonly semi-naturalised 'in the wild' in lowland B & I, chiefly in the southern half of England and in Wales, while remaining only rare and thinly scattered in Ireland. Around 18 additional species and hybrids of the genus are also reported in Britain as rare or very rare casuals (Clement & Foster 1994).

The biennial O. glazioviana is the most frequent and widespread of the four species that regularly appear as B & I garden escapes and it displays a definite preference for sandy soils, both at the coast and inland (C.A. Stace, in: Preston et al. 2002). It flowers from June to September and bears its stigmas above the anthers and, therefore, is more likely than other species to outbreed, and hence to form hybrids (Stace & Crawley 2015).

It has long been argued that this species arose in Europe in recent centuries, where it is established locally in northern and central regions, rather than it being a native of America like the rest of the genus (Clapham et al. 1962). It could be a neonative, evolved in Europe by mutation and hybridisation; if this were the case, it would be a second British case of homoploid hybrid speciation, in addition to that of Oxford Ragwort (Senecio squalidus) (Stace & Crawley 2015).

There are just three records of this large flowered species in the Fermanagh Flora Database, all found in and around Enniskillen town. In addition to the first record listed above, the other two records are: ten plants on waste ground behind the old town jail, 19 July 2006, RHN; and Silverhill, Enniskillen, 6 October 2006, RHN.

O. glazioviana (= O. erythrosepala Borbás) is a tall plant, approaching 2 m in height, with numerous large pale yellow flowers which seed profusely. Unlike Epilobium species (willowherbs), the seed is not plumed. The seed output of this and related species is so huge however, that it is now being exploited commercially, both as an oil-seed crop and for its beneficial effects in medicine (Gwynn Ellis 1993).

O. glazioviana typically colonises open vegetation in waste places, car parks, roadsides and other forms of disturbed ground (including railway ground, where this survives). At the coast, it invades sand dunes, the equivalent natural vegetation. While large populations can rapidly develop in freshly opened, disturbed ground, these usually decline equally quickly as the vegetation closes, so that the species may be regarded as a non-persistent pioneer colonist or casual.

The genus Oenothera seems to have become more popular and fashionable with Irish gardeners during the 1970s, since the majority of records on the island post-date this period and they have increased from rarity to occasional in status. This species is still only reported from seven Irish VCs, four of them in NI (ie H33 & H38-H40) (Cen Cat Fl Ir 2; Cat Alien Pl Ir). We expect to see more of this attractive alien in Fermanagh in the future.

Threats

None.