Lamium hybridum Vill., Cut-leaved Dead-nettle

Account Summary

Growth form, identification and preferred habitats

This annual ruderal weed of cultivated ground and disturbed waste places can behave as either a winter or a summer annual. L. hybridum grows up to around 25 cm tall and, like L. purpureum with which it is most often confused, it flowers from March to October and is pollinated by bees.

L. hybridum appears to perform best as a pioneer colonist when exploiting, sunny, warm, dry, heavily fertilised, moderately acid soils, such as those used for broad-leaved crops, including potatoes. It colonises the edges of fertile, arable fields, roadsides and wayside tracks (Sinker et al. 1985; K. Walker, in: Preston et al. 2002).

As the English common name suggests, Cut-leaved Dead-nettle can be distinguished from the more common and widespread L. purpureum by its more deeply and irregularly toothed leaves (many teeth being longer than 2 mm). The plant is more slender and less pubescent than L. purpureum, the leaves often smaller, the upper ones truncate at the base (not cordate) and ± decurrent down the petiole. In addition, the ring of hairs on the inner surface of the corolla tube near its base, that is such a well-marked characteristic of L. purpureum, is only weakly reproduced, if present at all, in L. hybridum (Garrard & Streeter 1983; Clapham et al. 1987; Webb et al. 1996).

Fermanagh occurrence

L. hybridum has been discovered five times in Fermanagh in recent years. The record details of the other finds are: disturbed ground by roadside halfway between Newtownbutler and Galloon Bridge, 1 September 2001, RHN & RSF; Lisgoole, Upper Lough Erne, 30 May 2004, RHN; Enniskillen town, 18 August 2008, RHN; and Gublusk Bay, Lower Lough Erne, 19 August 2008, RHN.

The occurrence of this annual weedy species in a potato field with ten other common ruderals is interesting in itself and suggests the possibility that it may be overlooked elsewhere. This is particularly the case if it occurs intermingled and is confused with the very similar L. purpureum (Red Dead-nettle), which it is reputed to do (An Irish Flora 1996; K. Walker, in: Preston et al. 2002).

The first Fermanagh record listed here means that L. hybridum has now been found in 33 of the 40 Irish VCs (Cen Cat Fl Ir 2).

British and Irish status and occurrence

L. hybridum is a rather local weed species, widely distributed, but perhaps only casually in its occurrence and rather scarce and local in most of B & I. The hectad map in the New Atlas shows it recorded right across the whole range of latitude from the Channel Isles to Shetland and frequently appearing in coastal squares, especially in the north. It also appears to be most frequently recorded in the E of England, south of the River Humber. In Ireland, it is more frequently recorded in NI than in the RoI, where it is most noticeably coastal in its occurrence (Preston et al. 2002).

Previously, like other members of the genus Lamium, Cut-leaved Dead-nettle was believed to be native in Britain (Clapham et al. 1987; Stace 1997) and possibly introduced in Ireland (Webb 1977; Webb et al. 1996). Along with all the other members of the genus it is now recognised as being an introduced archaeophyte in B & I (Preston et al. 2004; Stace 2010). The New Atlas hectad map indicates that it has greatly increased in recent years, presumably due to the widespread generous use of chemical fertilisers and slurry spraying on fields. Confusion with L. purpureum means L. hybridum is still very probably under-recorded and the former over-recorded (K. Walker, in: Preston et al. 2002).

European and world occurrence

The geographical origin of this weedy dead-nettle is unknown, but it is distributed over large parts of Europe and adjacent parts of Africa (ie Morocco and Algeria (where it is rare)). The main areas of lesser presence (or absence) are in E & SE Europe (Hultén & Fries 1986, Map 1591; Clapham et al. 1987).

Threats

None.

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