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Saxifraga umbrosa × S. spathularis
(S. × urbium D.A. Webb), Londonpride

Account Summary

Introduced, neophyte, an occasional garden escape.

May 1845; Smith, T.O.; Ardunshin Bridge, on the Colebrooke River.

Throughout the year.

The parent species of this hybrid do not overlap in the wild, although their geographic distributions are not far apart: S. umbrosa is confined as a native to the Pyrenees, while S. spathularis ranges from N Portugal, NW Spain to SW Ireland. The two species must have met and crossed in cultivation to form the sterile hybrid, sometime in the 17th or early 18th century (Stace et al. 2015). The hybrid nature of the plant was not recognised until D.A. Webb's (1950b) study of the so-called 'Robertsonian saxifrages' group.

Londonpride was once a very common and popular garden plant on account of its vigorous growth, prolific flowering and tolerance of shade, poor, dry soil, soot and occasional, prolonged neglect. It is both easy to grow and very simple to divide and propagate, again adding to its popularity well beyond the confines of the alpine or rock garden enthusiast. With the rapid development of commercial garden centres from the 1960s onwards and the subsequent availability of a greatly increased range of competing garden plant material, Londonpride has inevitably lost some of its past popularity.

Since the plant does not produce seed, stations recorded beyond the garden wall must represent surviving discarded garden material. Typical sites include damp, shady woods and scrub, by streams, on rocks, walls, hedge- and ditch-banks, roadside verges, disused quarries and church- and graveyards.

Fermanagh occurrence

In Fermanagh, this very familiar evergreen, rosette-forming, stoloniferous, perennial hybrid has been recorded in 15 tetrads (2.8%), scattered across the VC. Patches of Londonpride are occasionally found in estate woodlands, but, unfortunately, also in shady and/or damp, generally lowland places where garden refuse is discarded. Locally this means anywhere roadside or near streams and rivers that is sufficiently remote from habitation, or concealed from public view for such 'fly tipping' to be unobserved. The plant is quite often found near bridges or other man-made structures, and it can be long persistent. Only the pollen of this hybrid is functional (Webb & Gornall 1989, p. 69), so that colonies persist and spread to a very limited extent, purely by lateral growth of vegetative stolons.

Irish occurrence

In NI, this garden hybrid is quite widely scattered and established, chiefly in Cos Fermanagh, Tyrone, Antrim and Londonderry (H33, H36, H39 & H40). Elsewhere in Ireland, it appears very much rarer and more sporadic in its distribution (Cat Alien Pl Ir; Stace et al. 2015). The map of S. × urbium published by Stace et al. (2015) plots 73 Irish hectads with records of any date, representing 7% cover on the island.

British occurrence

In Britain, S. × urbium was first noted in the wild in 1837, and is now frequent and widely scattered throughout all latitudes, although with a definite western predominance in its distribution (New Atlas; Stace et al. 2015). The map in Stace et al. (2015) plots a total of 719 hectads with records of the hybrid of any date. This represents 25% cover in Britain, emphasising a major difference between B & I that may represent recorder and/or gardener effort. While this hybrid is normally male fertile only and does not set seed, according to Webb 1950b and D.A. Webb, in: Stace (1975), there are some fertile clones in existence (eg in Orkney).

European occurrence

This hybrid in Europe is often sold and cultivated under the name S. umbrosa, and is reported common in C Europe (Essl 2004). It is naturalised in France and in scattered localities in Austria, where it was first recorded in 1881 (Essl 2004).

Threats

Although it naturalises perfectly well in woods and by shady streams, locally this evergreen perennial is not frequent enough to be a threat.