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BIODIVERSITY REFERENCE
 
   Orobanche L.   
 
Broomrapes
 
(page 2)


Orobanche alba Stephan ex. Willd. (= O. rubra Sm.) (Thyme Broomrape)

Orobanche alba, Cornwall
Orobanche alba in serpentine turf, Lizard Peninsula, Cornwall, 1991

 
A parasite of Wild Thyme (Thymus polytrichus) on basic (e.g. limestone) and ultra-basic rocks (e.g. serpentine, basalt), and mainly on sea-cliffs.
It has three main areas of occurrence in Britain:
i) Cornwall (S.W. England), where it has vanished from a number of localities but still survives on the serpentine cliffs of the Lizard Peninsula;
ii) inland limestone cliffs in northern England;
iii) sea-cliffs of western Scotland, where it has seemingly gone from many sites but is likely overlooked in others, perhaps on inaccessible ledges.
It is very scattered and mostly extinct elsewhere. It is rated 'nationally scarce' and its recent status is summarised by M.J.Y. Foley (in Stewart et al., 1994). It is widespread and not yet endangered in Europe and is somewhat less restricted in choice of host.


 

Orobanche alba, Isle of Harris
Orobanche alba, Isle of Harris, flowring spike in bud
Orobanche alba, Isle of Harris
Orobanche alba, Isle of Harris, flowers in close-up
Orobanche alba on sea-cliffs, Harris, Outer Hebrides, July 2006.


 
 

Orobanche caryophyllacea Sm. (Clove-scented Broomrape)

Orobanche caryophyllacea, Kent

 
A parasite of bedstraw Galium species, especially Lady's Bedstraw (G. verum) in its main British site but also on Hedge Bedstraw (G. mollugo) (and also on young plants of what appeared to be the hybrid between the two at the time of this photograph). It is confined to the coast of a small area of East Kent, best known on coastal dunes, where it grows in the company of other nationally rare species, but it also has small populations on chalk sea-cliffs. A very few other old British records all appear to be errors or misrepresentations.

Its British distribution is something of a mystery, since it implies a plant that requires warm and dry conditions, just gaining a foothold in Britain at a climatic limit. However, it occurs widely in Europe, including the Alps and Scandinavia. Perhaps it was a late arrival across the postglacial land bridge between Kent and France, before the English Channel formed, and since it appears to be obligately outbreeding, this may have limited its further chances of spread. An alternative theory is that it has arrived by wind-blown seed from France. Today it seems secure at least in its main site, though even there, a high grade piece of ground in private hands currently (2002) seems likely to be lost. Its conservation status is summarised by M. Jones (in Wigginton, 1999); it is listed as VULNERABLE and it is a scheduled protected plant under the Wildlife and Countryside Act, 1981.

As indicated by the name, the flowers have a distinctive scent of cloves.

 
Photograph: In dry, dune grassland, East Kent, June 2002.


 
 
 

Orobanche elatior Sutton (Tall Broomrape)

Orobanche elatior, Norfolk

 
A perennial parasite on Greater Knapweed (Centaurea scabiosa). It occurs (as is the tendency of its host) mainly on calcium-rich soils (chalk, chalky boulder-clay and soft limestones) in southern and eastern England, but it is absent from the western part of its host's range.
It is one of the tallest of our species and the persistent dead stems can attract attention, yet it is easily overlooked in shady hedges and on woodland margins.

It is only locally frequent within its range and shows some evidence of decline, but it remains as our only species other than O. minor that is not rated as nationally scarce or nationally rare.

 
Photograph: Hunstanton, Norfolk, 1966.


 
 
 

Orobanche rapum-genistae Thuill. (Greater Broomrape)

Orobanche rapum-genistae, Isle of Wight

 
A perennial parasite principally on Broom (Cytisus scoparius) and Gorse (Ulex europaeus).

In the past, regarded as locally frequent throughout England and Wales, though scarcely reaching Scotland. However, over the past century, it has shown a dramatic decline, vanishing even where habitats seemed to remain suitable, and it appeared it might even be heading for extinction. Even so, it has held on in scattered sites, especially near the coast and in the south-west, and perhaps it is even showing signs of recovery. Its changes of distribution and recent status are described by Foley, in Stewart et al. (1994).

It has to be said that the location where it was photographed was remarkably unremarkable, and it must surely be overlooked elsewhere within uninviting gorse thickets!

 
Photographs: Isle of Wight, May 2004 (BSBI meeting), flash photographs of a shaded and well-hidden colony behind a gorse (Ulex) thicket on the edge of woodland.


Orobanche rapum-genistae, Isle of Wight


 
 

Orobanche hederae Duby (Ivy Broomrape)

Orobanche hederae, Wigtownshire

 
As the name implies, this is largely parasitic on Ivy (Hedera helix), exclusively so in its native sites in Britain. In fact native populations are almost all on the tetraploid ivy race, H. helix subsp. hibernica, which extends up the west coast of Britain to south-west Scotland. Consequently, native British O. hederae sites are almost all on sea-cliffs on the S.W.English and Welsh coasts, plus one single locality in Galloway. The Scottish locality contains a healthy population (source of the photographs used here) and is noteworthy for outlying populations of other southern plants.

However, this rather neat native distribution is somewhat belied by the occasional occurrence of this species as an accidental or deliberate introduction on cultivated ivies, notably Hedera colchica, and on other cultivated members of the ivy family (Araliaceae) in inland gardens. In Europe it occurs widely, though sparsely, across much of southern and south-western Europe, evidently on the widespread ivy subspecies, H. helix subsp. helix, that it largely ignores in Britain. Possibly there is some ecotypic variation within the species?

O. hederae is rated a 'nationally scarce' species though not currently considered to be at any risk (Rumsey, in Stewart et al., 1994).

 
Photographs: Sheltered sea-cliffs, Wigtownshire, S.W. Scotland, 1997.


Orobanche hederae, Wigtownshire


 

Orobanche picridis F.W. Schultz ex Koch (Oxtongue Broomrape)

Orobanche picridis, Kent

 
Perhaps the rarest broomrape in Britain, recorded (with varying degrees of certainty) from a very few scattered sites in southern England and Wales and probably now confined to one site on the Isle of Wight and two in East Kent. It is a parasite of members of the family Asteraceae, particularly Hawkweed Oxtongue (Picris hieracioides).

In Europe it also (but rarely) parasitises Carrot (Daucus carota). It is widespread, but very rare and scattered, across the whole of southern Europe.

It appears to require dry, sunny slopes on lime-rich soils and the extant sites are on unstable, chalk seacliffs, where population sizes fluctuate from one year to another. Its conservation status is summarised by M.J.Y. Foley (in Wigginton, 1999); it is listed as ENDANGERED and it is a scheduled protected plant under the Wildlife and Countryside Act, 1981.

Nomenclatural note: Recent British authorities have considered this species to be the same as O. artemisiae-campestris (= O. loricata), a very rare and local parasite of Field Mugwort (Artemisia campestris) in southern and central Europe. Kreutz (1995) maintains them as separate species and that view is followed here (though they might be better considered as subspecies).

 
Photograph: East Kent, 1972 (encountered by chance but evidently one of the known sites).


 
 

Other British species

As yet I have no photographs of O. purpurea, the Yarrow Broomrape, a very scarce and scattered species in southern England and Wales, or of O. reticulata, the Thistle Broomrape, which occurs, as its subsp. pallidiflora, on the Magnesian Limestone of South Yorkshire. Established introductions in Britain include O. crenata in South Essex (see page 1) and O. lucorum, the Barberry Broomrape, deliberately introduced in St. Andrews, Fife (Ballantyne, 2010).


References
•   Ballantyne, G.H., (2010). Orobanche lucorum (Barberry Broomrape) in Fife (v.c.85). BSBI News 113: 57.
•   Kreutz, C.A.J., (1995). Orobanche: die Sommerwurtzarten Europas: ein Bestimmungsbuch (= the European broomrape species: a field guide). 1. Mittel- und Nordeuropa (= Central and Northern Europe). Stichtung Natuurpublicaties, Limburg.
•   Rumsey, F.J., (2007). A reconsideration of Orobanche maritima Pugsley (Orobanchaceae) and related taxa in southern England and the Channel Islands. Watsonia 26: 473-476.
•   Rumsey, F.J., & Jury, S.L., (1991). An account of Orobanche L. in Britain and Ireland. Watsonia 18: 257-295.
•   Sell, P.D., & Murrell, G., (2009). Flora of Great Britain and Ireland, 3: Mimosaceae – Lentibulariaceae, Cambridge University Press, Cambridge.
•   Stewart, A., Pearman, D.A., & Preston, C.D., eds., (1994). Scarce plants in Britain, JNCC, Peterborough.
•   Wigginton, M.J., ed., (1999). British Red Data Books, 1. Vascular plants, 3rd ed., JNCC, Peterborough.


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