Probably perennial, this root parasite of thistles occurs in rough grassland, on road verges, and especially on river margins and flood plains where its frequent, sometimes transient, occurrence suggests that seed is readily dispersed by water. It is almost restricted to Magnesian limestone districts. Lowland.
The distribution of O. reticulata appears to be stable, although many new populations have recently been found.
European Temperate element, with a continental distribution in W. Europe; also in C. Asia. Our plant is subsp. procera, which has a lowland distribution in Europe and is quite distinct from the montane subsp. reticulata.
Height (cm): 60
Perennation - primary
Perennation - secondary
Life Form - primary
Life Form - secondary
Clonality - primary
Count of 10km squares in Great Britain: 7
Count of 10km squares in Ireland: 0
Count of 10km squares in the Channel Isles: 0
RDB Species Accounts
Orobanche reticulata Wallr. (Orobanchaceae)
Status in Britain: LOWER RISK - Near Threatened. WCA Schedule 8. The British taxon is perhaps ENDEMIC.
Status in Europe: Not threatened.
In Britain, O. reticulata is restricted to Yorkshire, where it was first identified as a British plant in 1909, though herbarium specimens pre-date this by at least 50 years. The great majority of its localities are on or close to the Magnesian limestone formation, with an outlier further east on the chalk. It is a root parasite of thistles, almost always (99% of plants) on Cirsium arvense, but very occasionally on C. eriophorum, C. heterophyllum, C. palustre, C. vulgare or Carduus nutans. Typical habitats are rough pastures, road verges, semi-natural grassland, and especially the banks of rivers and flood plains with associated light scrub, though not where ground is permanently waterlogged. Its most frequent associates are Arrhenatherum elatius, Cruciata laevipes, Dactylis glomerata, Festuca rubra, Glechoma hederacea, Ranunculus repens and sparse Rubus fruticosus and Urtica dioica. In moister habitats, it may occur with Filipendula ulmaria, Impatiens glandulifera and Petasites hybridus (Abbott 1996).
This species is possibly perennial in certain situations, but otherwise behaves as an annual or biennial, appearing above ground in July. Seed setting is usually good, and the small seed readily dispersed. Water-borne seed dispersal appears to be very efficient, as evidenced by its tendency to occur at or close to river margins, although existing plants along with their host may additionally be displaced and relocated by flood water. Nevertheless, even in areas where it is frequent, vast stands of thistle remain unparasitised, the controlling ecological factors remaining largely unknown. It tends to be absent from the more dense vegetation and usually parasitises smaller, relatively immature host plants. Dead spikes can persist well into the winter and sometimes remain until the following flowering season. Its appearance in newly-cleared sites (even woodland) strongly suggests that seed remains viable for many years (Abbott 1996).
Most of its locations are in the valleys of the Ure and Wharfe, where it seems to have increased in recent years; however there is at least one strong colony on a roadside verge away from river influences. A recent survey established that of 70 separate recorded populations, 54 were extant, and more than 85% of these were within the influence of river flood-water (Foley 1993). Numbers vary considerably from one year to the next, but it has the ability to persist even in small colonies, some of which are still extant after a period of 80 years or more. Most populations are small (1-50 plants), but a few regularly exceed 100, though the largest held 787 spikes in 1995, following soil disturbance. It seems to do particularly well in hot summers. Its occurrence close to Roman roads and settlements has led to suggestions that it might have been an early introduction (e.g. Pugsley 1926), but more recent studies support its claim to native status.
The main threat to its survival results from the deliberate destruction of its hosts, many of which are serious agricultural weeds. Other damaging activities, especially ploughing and spraying, road construction, and gravel extraction, all pose additional threats. It will not thrive in shade, or in tall grass, and clearance of dense stands of tall Urtica dioica would benefit some colonies (Abbott 1995). Opening up the turf and disturbance of the ground have resulted in increased populations at some sites. Rabbit activity may likewise be a positive asset.
O. reticulata is recorded from much of Europe and especially the alpine region. It apparently extends eastwards into Russia and western Asia and is also recorded from North Africa. Towards the northern limits of its range it exhibits a more disjunct distribution pattern as shown by its occurrence in Britain, Scandinavia, the Baltic states, the Netherlands and northern Germany. Outside Britain, several variants and subspecies have been recorded. The exact status of the British plant which was formerly referred to var. procera, is not fully understood and the taxonomy of the European members of this group is currently under investigation. Kreutz (1995) regards the British plant as a separate species - O. pallidiflora Wimmer & Grabowski (O. reticulata ssp. pallidiflora (Wimmer & Grabowski) Hayek).
M. J. Y. Foley
PLANTATT - Attributes of British and Irish plants. (.zip 1455KB) This dataset was compiled and published in 2004, and last updated in November 2008. Download includes an Excel spreadsheet of the attributes, and a PDF explaining the background and nomenclature. Note that the PDF version is the booklet as published, whereas the Excel spreadsheet incorporates subsequent corrections. A hardcopy can be purchased from the Centre for Ecology and Hydrology.
Atlas text references
1986. Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
1978. Vergleichende Chorologie der zentraleuropäischen Flora. Volume 2. 2 vols.
1998. Management and conservation status of sites with Orobanche reticulata Wallr. Populations. The Naturalist. 123:70-75.
1991. An account of Orobanche L. in Britain and Ireland. Watsonia. 18:257-295.
1999. British Red Data Books. 1. Vascular plants, edn 3.