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  • Writer's pictureSim Elliott

182 spikes of Knapweed Broomrape, Orobanche elatior, at a South Downs site. 13.06.23

Updated: Jun 26

46 photos of 182 spikes of Knapweed Broomrape, Orobanche elatior, at one site on the South Downs. The location of this cluster of O. elatior is not given. No photographs are included that might reveal the location.

I am an amateur naturalist (and retired teacher) who walks around the countryside of Sussex a lot; I am not a professional botanist!

All sections of text in italics are quotations, sources cited.

Photographs are in chronological order of my observations

Text from Botanical Society of Britain and Ireland Plant Atlas 2020 listing

Knapweed Broomrape Orobanche elatior Sutton Orobanche elatior Sutton in BSBI Online Plant Atlas 2020 eds P.A. Stroh, T. A. Humphrey, R.J. Burkmar, O.L. Pescott, D.B. Roy, & K.J. Walker. [Accessed 14/06/2023]

There appears to have been a gradual contraction in the range of O. elatior, especially in areas outside its core range where populations tend to be small. Most losses are probably due to habitat destruction, or long-term neglect. The distribution is apparently stable in its core areas. Biogeography Eurosiberian Temperate element, with a continental distribution in western Europe. Authors M.J.Y. Foley

The text of the section concerning Orobanche elatior, in "An account of Orobanche L. in Britain and Ireland" J. RUMSEY and S. L. JURY. Department of Botany, University of Reading, P.O. Box 221, Reading, Berkshire, RG6 2AS Watsonia, 18, 257-295 (1991), is quoted at the end of this post.


An account of Orobanche L. in Britain and Ireland J. RUMSEY and S. L. JURY Department of Botany, University of Reading, P.O. Box 221, Reading, Berkshire, RG6 2AS Watsonia, 18, 257-295 (1991) Wats18p257.pdf ( accessed 14.06.23


Morphological descriptions are given of the 14 species of Orobanche (Orobanchaceae) recorded in the British Isles, together with separate keys for identifying fresh material and herbarium specimens. Accounts of the history of the species are presented together with illustrations and distribution maps. ...


The genus Orobanche is renowned as a taxonomically very difficult one. In most cases this is a result of many of the useful characters becoming lost on drying, and the lack of adequate field notes. Plants which are very distinct in the field become reduced to a hideous brown uniformity when pressed. Therefore, herbarium specimens are often incorrectly determined (an average of 5-10% in fact). The loss of characters on drying, considerable intra-specific variation, confusing synonymies, incorrectly cited names and badly described species with poor types (often with different species on the same sheet) have done little to generate interest in the genus. Too many botanists have shown a reluctance to deal with this genus in herbaria, perpetuating the myth that the species are impossible to identify once dried. Certainly, Orobanche minor Sm. and its close relatives often cannot be positively determined without descriptive notes made at the time of gathering, but all other species from the British Isles are distinct enough not to need any additional information.

It is hoped that this account will stimulate other botanists to study, identify and record members of this fascinating parasitic genus in Britain and Ireland, as well as clear up some errors and confusions made in the past.

If more than one English name is in common usage, then they are all given, but the first is the name recommended by Dony, Jury & PeTTing (1986).

Chromosome numbers are given where known. Counts from British material (Hambler 1958) are marked by an asterisk. All other counts are from European material (Moore 1982).

Distribution maps are based on herb~um material from BM, CGE, E, K, LIV, MANCH, NMW and RNG, together with selected records from the Biological Records Centre.


Populations of Orobanche species are often enormously variable with regard to such characters as size, colouration and pubescence, yet these details are seldom recorded on specimen labels. Because of this variation and their use in the taxonomy of the genus, care should be taken not to rely on a single character in isolation.

Most of the British species have a restricted host range and it is therefore important to identify and record this. Unfortunately, this seemingly simple task is often almost impossible: it is not easy (nor often desirable!) to dig up the plants to observe connections between host and parasite. If the host species has to be guessed, this should be stated, and other surrounding species noted. Too often an incorrect plant has been given as the host and this has wrongly influenced later determination.

Other characters to pay particular attention to include: the overall stature of the plant; the degree of swelling at the base (though where a species has several host species, such as Orobanche minor, these host taxa will obviously influence the Orobanche morphology): colour and degree of stem 258 F. J. RUMSEY AND S. L. JURY pubescence; length and pubescence of bracts; presence or absence of bracteoles; length, shape and venation of the calyx (though this may vary considerably on a single plant); position, shape and size of the lobes of the upper and lower corolla lips, the height of insertion of the stamens, the position and degree of the stamen pubescence, and the colour and degree of fusion of the stigma lobes.

Pubescence of the anthers has been used as an important diagnostic character for taxa within section Trionychon Wallr. but not for those within other sections of the genus (Webb & Chater 1972). All British taxa of section Orobanche have hairless anthers.

Preliminary investigations of seed morphology (Rumsey unpubl.) reveal great variability in size and shape from single capsules and preclude reliable discrimination of the taxa considered here with a single exception. O. ramosa L. subsp. ramosa is distinct in having a secondary layer of reticulation to the surface of the cells and not just the small circular to ovoid pits seen in all other British taxa. ...

8. O. elatior Sutton in Trans. Linn. Soc. Lond. 4: 178 (1797). O. major L., pro parte.

English name: Tall Broomrape.

Illustrations: Figs 2A, 5C. Photographs in Strid (1980: pl. 63), Petch & Swann (1968: pl. 73); drawings in Garrard & Streeter (1983: 150), Ross-Craig (1966: pl. 25), Butcher (1961: 287), Martin (1965 pl 66)

Flowering stem simple, (15-)25-70 col, usually stout, yellowish to orange, often with a rather bulbous base, usually glandular pubescent. Flowers numerous, usually densely packed, often confined to the top third of the stem. Bracts 15-25 mm, lanceolate, acuminate. Calyx (6-)9-11 mm, segments connate at base, usually unequally bidentate. Corolla 18-25 mm, yellow or orange with reddish-brown veins; uniformly curved throughout, widely tubular, glandular-pubescent, sub-erect to erecto-patent, sometimes patent; upper lip :t entire, or more often two-lobed, usually spreading; lower lip three-lobed, the lobes nearly equal, crisped, denticulate. Stamens inserted 3-6 mm above the base of the corolla tube; filaments hairy below, glandular throughout. Stigma lobes yellow. Flowering period mid-June to August. 2n=38. Native, usually parasitic on Centaurea.

This plant was described by Sutton (1797), but has been the centre of a taxonomic wrangle causing a great deal of confusion. This stems from the inadequate description of O. major, together with a confusing array of synonyms. Orobanche major has been interpreted to include O. elatior, O. rapum-genistae and larger specimens of O. minor! British and French botanists used the name O. major for Orobanche rapum-genistae, while Beck-Mannagetta (1930) assigned Orobanche elatior to this, citing Linnaeus's Flora Suecica of 1755; O. elatior is a Swedish plant, while O. rapum-genistae is not. However, in the second edition of his Species Plantarum, Linnaeus (1763) states clearly that the plant grows on the roots of Leguminosae. Linnaeus did not understand Orobanche at all well! There is a sheet in LINN on which two specimens are mounted, these having been sent to Linnaeus by Loefling, and were inscribed "Orobanche major" by Linnaeus. Sir James Smith saw these and annotated the sheet "minor Mr. Sutton". Later, Hooker was to claim no sheet of Orobanche major existed in the herbarium. Pugsley examined the sheet and considered the plants most like Orobanche picridis. He hoped that the specific identity of the plants could be established, so that O. major L. could be validated. We have examined the sheet and believe the two specimens belong to different species. The left, which has been attacked by beetles, does indeed look quite like O. picridis; however, we do not believe it is. We consider it is probably a pale form of Orobanche crenata Forskal, a plant which would be found in the area Loefling collected from. The flowers are 20-25 mm with straight backs and erect upper lips. The right hand plant suggests O. elatior, but examination of an opened corolla of this plant showed a stamen insertion of 2-4 mm and glabrous filaments. Such a combination of characters seems to rule out Orobanche elatior. Because of this, and the overall confusion, it would seem necessary to reject the name O. major L.

In Britain, Orobanche elatior grows almost exclusively on Centaurea scabiosa L., but it has been reported on Centaurea nigra L. The habitat preference of the host largely determines the parasite's distribution but O. elatior is more restricted to chalk and Jurassic limestones. Early authors stated that this plant grows on Trifolium pratense L. Confusion with large states of O. minor is probable in many cases. Where the plant is correctly identified, it is probable that the wrong host was given as it is often difficult to trace the root systems.

The plant grows on chalk downs, in disused chalk pits, on roadsides, etc. It is a perennial and may throw up a large clump of flower spikes from a single host. The previous year's flower spikes often persist and may be found next to the new spikes. The plant is of a characteristic colour with a yellowish stem, and usually pinkish- to yellowish-brown flowers; however, f. citrina (Druce) Pugsley has the whole plant citron yellow. The plant may be confused when small with O. minor, but only var. compositarum has the suberect corollas so often found in O. elatior. The flowers are broader in o. elatior, have conspicuous brown veins and are more glandular, while the whole plant has a distinctly different look about it, difficult to describe. This species is somewhat local and many of its sites would be threatened by land-use changes. It is still tolerably plentiful, especially in Wiltshire and northern Essex/Cambridgeshire. However, it is decreasing towards the western and northern extremities of its range, possibly for climatic reasons. A summary of its distribution is given in Fig. 14.

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