46 photos of 25 spikes of Common Broomrape, Orobanche minor, 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.
Common Broomrape, Orobanche minor Sm. Orobanche minor Sm. in BSBI Online Plant Atlas 2020 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. https://plantatlas2020.org/atlas/2cd4p9h.cb4 [Accessed 14/06/2023]
Common Broomrape Orobanche minor Sm.
This usually annual root parasite occurs on a wide range of hosts, but mainly on species of Fabaceae and Asteraceae. Speciation is apparently underway, driven through host specificity with genetically distinct but poorly morphologically defined lineages now recognized as infra-specific taxa (Thorogood & Rumsey, 2021). This process may be recent, with O. minor var. heliophila primarily parasitizing Brachyglottis × jubar, a host only introduced to Britain in the 20th century. The most frequent of these taxa, var. minor, is probably alien and is usually found on cultivated land (often introduced with grass or fodder crop seed) and other disturbed ground. However other taxa are native, with subsp. maritima found on cliffs and dunes on the south coast, with Daucus carota subsp. gummifer as its main host. Lowland. Native in Britain and the Channel Islands and a neophyte in Ireland.
The frequent introductions of this species give it a dynamic distribution, so that long-term trends in frequency are difficult to assess. The native subspecies and variants appear to be stable, although scrub encroachment on coastal slopes and damage to beach and dune systems may be having some negative impact. Var. heliophila has increased markedly in urban and amenity areas where its host is widely planted. Biogeography European Southern-temperate element; widely naturalized outside its native range. Authors F.J. Rumsey and M.J.Y. Foley
O minor from 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 (bsbi.org.uk) accessed 14.06.23
10. O. minor Sm., Eng. Bot. 6: 422 (1797). O. minor Sutton in Trans. Linn. Soc. Land. 4: 179 (1797).
English names: Common Broomrape, Lesser Broomrape I
llustrations: Figs 3B-E, 6G, D, 7A-B. Photographs in Polunin (1969: pl. 131), Gilmour & Walters (1954: pl. 22), Philp (1982: 196 as O. amethystea); drawings in Martin (1%5: pl. 66), Garrard & Streeter (1983: 149), Butcher (1961, 2: 289).
Flowering stems simple, (5-)10--60 cm, glandular-puberulent to hairy, yellow or reddish-brown variously tinged purple. Spike lax to dense. Bracts 6-22 mm ovate-lanceolate to lanceolatesubulate, acuminate, :t equalling to just exceeding the corolla. Calyx 6-14 mm long equally to unequally bifid or entire. Corolla 10-18 mm, creamy-yellow, curved regularly throughout or sharply inflected at the base then curved, purplish suffused to a variable extent, glandular- pubescent to :t glabrous, upper lip emarginate or slightly bilobed with the lobes directed forwards; lobes of lower lip sub-equal or with the central the largest, all lobes crisped and denticulate. Stamens inserted 2-3.5 mm above the corolla base; filaments glabrous to sparsely hairy below. Stigma lobes yellow or reddish-purple, just touching at base to partially united. Flowering period late May to mid September. n = 19, 2n = 38. Probably native but frequently introduced, a parasite of many families.
Undoubtedly our most common broomrape, which makes its date of description all the more remarkable. It is likely that the early English botanists confused this species with many of the other members of the genus but even allowing for such confusion it would seem to have greatly increased in this country, probably through repeated introduction with fodder crops. Cleaner seed and changes in agricultural practice would seem to have caused some decline. Webb (1985) has questioned the native status of this species in the British Isles; it is unquestionably an introduction in Ireland where it occupies similar habitats. Its indigenous range is now unclear through man's activities. O. minor exemplifies the taxonomic difficulties posed by the genus. As with many parasitic groups, morphological reduction has deprived the taxonomist of diagnostic characters. This, when combined with the largely unknown host-determined effects on parasitic morphology and phenology, makes classification problematic. Seeds similar to those of O. elatior, with few 'cells' on the surface. Seed size and shape are very variable and are not of use in distinguishing the infraspecific taxa in the O. minor agg. Of all the Orobanche species O. minor has the most catholic tastes with regard to hosts, hundreds of species in families from the Ranunculaceae to the Gramineae are attacked but a clear preference is shown for the Leguminosae and Compositae. Cultivation experiments which could determine the influence of the host and degree of host specificity are difficult to perform. Musselmann & Parker (1982) have shown that races of O. minor physiologically adapted to certain hosts exist and it is easy to visualise speciation progressing along these lines. O. minor has efficient seed dispersal and is largely inbreeding; accordingly populations preferentially parasitizing a species which has its own distinct ecological preferences may become effectively isolated and ultimately give rise to distinct taxa. Recognition of these by traditional means is only possible where subtle morphological differences have paralleled the more profound but invisible physiological changes; such morphological characters may be of lesser selective importance. As so little is known of the cytology and physiology of O. minor sensu lato, the following treatment is perhaps best regarded as provisional. We conclude it best to regard O. minor in Britain and Ireland as consisting of four varieties which can be distinguished as follows.
Key to the varieties of Orobanche minor:
1. Plant yellow., to 25 cm, rarely more, spike dense almost sub-globose. Stigma lobes yellow. Host usually Hypochaeris radicata lOc. Val. /lava
1. Plant purple., to 60 cm, spike lax to dense above. Stigma lobes reddish brown to purple. Hosts various 2
2. Flowers sub-erect at anthesis, slender, ca 3.5-5.0 rnrn diameter, pale, sub-glabrous. Hosts usually Crepis spp. and other Compositae lOb. var. compositarum
2. Flowers patent to erecto-patent, ca 5.0-8.0 mm diameter, :t suffused purple, glandular 270 F. J. RUMSEY AND S. L. JURY pubescent to sub-glabrous. Hosts various
3. Plant with bulbous base, stem glandular-puberulent, to 35 cm. Bracts not exceeding corolla. Calyx short, 6--10 mm, usually entire. Lower lip with middle lobe the largest, reniform. Stigma lobes partially fused. Host almost exclusively Daucus carota subsp. gummifer 10d. var. maritima
Plant usually without 'bulb' at base, stem sub-glabrous to glandular-pubescent to 60 cm. Bracts equalling to exceeding corolla. Calyx ca 7.5-16 mm, bifid or entire. Lower lip with subequal broadly rounded lobes. Stigma lobes scarcely fused becoming distant with age. Hosts various 10a. var. minor * Rarely individuals without purple pigmentation but otherwise identical to var. minor occur, to which they are best referred. Similar pigment-less variants exist in other Orobanche species, e.g. O. hederae. O. elatior and O. crenata.
10a a. var. minor I
Illustrations: Figs 3B, 6C.
Flowering stems (5-)10--60 cm, glandular-pubescent, reddish-brown tinged purple, rarely yellow. Spike usually lax below ± dense above. Bracts 7-22 mm ovate-lanceolate equalling or exceeding the corollas. Calyx 7-14 mm equally or unequally bifid or entire. Corolla 10-18 mm glandular pubescent to sub-glabrous, back ± regularly curved; upper lip emarginate to bilobed, forwardly directed rarely ± sub-erect; lower lip with sub-equal lobes, all crisped and denticulate. Filaments glabrous to sparsely hairy below inserted 2-3.5 mm above corolla base. Stigma lobes purplish, touching at base becoming more distant with age. Flowering period late May to mid September. 2n = 38*.
A highly variable and widespread plant, possibly not native. Its appearances are often casual or sporadic. Most commonly encountered on roadsides, in disused chalk and gravel pits and on 'grey' dunes in coastal areas. It is becoming increasingly common as a weed in flowerbeds where the usual hosts are shrubby Senecio spp. A summary of its distribution (based on all records of the species, other than those attributed to the rarer varieties) is given in Fig. 16.
We include in this taxon the plants referred to the Mediterranean species O. amethystea Thuill. by Philp (1982). Some of the Kent plants do approach this in some respects but O. amethystea has larger flowers with a distinctly bilobed, sub-erect upper lip and a higher filament insertion. The population at Sandwich consists of plants parasitic on a wide range of hosts, including Eryngium maritimum, Ononis repens, Calystegia soldanella, Honkenya peploides and Elymus farctus. The host influence on stature and pigmentation is apparent and a full range of intermediates between O. amethystea sensu Philp and typical O. minor can readily be found.
Occasional pigment-less variants are found, indeed the type sheet at LINN contains just such, as well as pigmented, material. We prefer not to treat the albino variant at varietal rank as it differs only in this respect and lacks the distinct morphological features, ecology and distribution shown by var. flava E. Regel.
10b. var. compositarum Pugsley in 1. Bot., Lond. 78: 111 (1940). I
Illustrations: Figs 3C, 6D.
Flowering stems 10-50 cm glandular pubescent to sub-glabrous, usually pale reddish-brown. Spike ± lax throughout. Bracts and calyx as in var. minor. Corolla 10-18 mm slenderer than in var. minor, sub-glabrous, sub-erect not horizontal at anthesis, less heavily pigmented. Other characters as var. minor.
A distinctive looking variant distinguished by its narrower, paler, sub-erect corollas. Pugsley (1940) claimed that the filament bases were hairier than usual for var. minor. This variety would appear to be thinly scattered throughout the British range of O. minor sensu stricto but is probably underrecorded. It would seem to be most frequent on sandy soils in Surrey, East Anglia and in coastal OROBANCHE IN BRITAIN AND IRELAND 271 areas elsewhere. Extra-British distribution is unknown. Host plants are, as the name would suggest, usually Compositae, Crepis virens being the most frequently recorded. Other hosts include Hypochaeris radicata, Tripleurospermum inodorum, Carduus nutans, Senecio greyii and exceptionally Smyrnium olusatrum. Specimens from Nob End, South Lancs., parasitic on Trifolium pratense are also probably best referred to this variety. Care should be taken when naming fruiting specimens as the corollas in var. minor may become increasingly erect with age.
10c. var. Oava E. Regel, in Otto & Dietrich, Allg. Gartenzeit. 284 (1842). O. minor Sm. var. lutea Tourlet in Bull. Soc. Bot. Fr. 1: 421 (1903). O. ritro Gren. & Godron f. hypochaeroides Beck ex Druce in J. Bot., Lond. 45: 425 (1907).
Illustrations: Figs 3D, 7A
Flowering stem 8-18(-25) cm, glandular-pubescent, yellow. Spike dense sometimes sub-globose. Bracts 6-14 mm, ovate lanceolate, equalling corollas. Calyx 6-10 mm, entire almost filiform. Corolla 10-14 mm, sparsely glandular, curved throughout but most sharply inflected at the base. Upper lip emarginate, lobes forwardly directed; lower lip with :t subequallobes, all crisped and denticulate. Filaments sub-glabrous, inserted 3-3.5 mm above corolla base. Stigma lobes yellow touching at base. Flowering period early June to mid July.
Plants referable to this taxon were first collected in the British Isles in 1866 by Syme at St Ouens, Jersey. It has subsequently been gathered here by many botanists under a confusing array of names (Pugsley 1940). Le Sueur (1984) incorrectly treated this taxon under O. elatior and suggested that it was destroyed by building during the Second World War. However, there is a specimen at LIV dated 1951. Other sites include Braye Bay, Alderney (Pugsley 1940) and Newport Docks, Glamorgan. Similar plants were reported as growing at Grand Havre, Guernsey by Syme in Sowerby (1866).
Unfortunately we have not been able to examine the types of var. flava E. Regel or var. lutea Tourlet and it is possible that they may be based on pigment-less variants of var. minor and therefore not be conspecific with the distinctive Channel Islands taxon. Similar plants have not been found elsewhere on coastal dune systems, suggesting the morphological features are not an environmental modification. This taxon would appear to us to be more closely related to var. maritima than to var. minor. Its continued existence in this country is somewhat precarious, the sole extant site being by a railway line in an area of dockland.
10d. var. maritima (Pugsley) Rumsey & Jury in Watsonia 17: 442 (1989) O. maritima Pugsley in J. Bot., Lond. 78: 110 (1940).
English name: Carrot Broomrape.
Illustrations: Figs 3E, 7B. Photograph in Sitwell (1984: 36, as O. loricata); drawings in Garrard & Streeter (1983: 149), Butcher (1961, 2: 291).
Flowering stem 10-30 (--40) cm, heavily pigmented with purple, glandular-puberulent, usually with a pronounced bulbous base from which several stems may arise. Flowers few to many in a dense spike. Bracts 8-16 mm, lanceolate from a broad base, usually not exceeding the corollas. Calyx 6-10 mm, entire or unequally bifid. Corolla 10-17 mm, sparsely glandular, sharply inflected at base; upper lip entire to emarginate; lower lip with middle lobe the largest, reniform, with pronounced yellowish bosses; all lobes crisped and denticulate. Filaments glabrous to sparsely hairy below, inserted 2-3 mm above the corolla base. Stigma lobes partially united, purple. Flowering period late May to early August.
This interesting variant can usually be distinguished from the widespread var. minor by the characters stressed in the key but these are not always easily seen in herbarium material. The squatter corollas densely packed in the top third of the spike is, however, a good indication of this ) minor var. maritima appears to be largely restricted to steep calcareous sea cliffs, where it almost exclusively parasitizes Daucus carota subsp. gummifer, but it is occasionally found in dune grasslands. Plants referrable to this taxon were first reported in Britain in 1845 by Rev. W. S. Hore. He collected it on the cliffs at Whitsand Bay, Cornwall and identified it as O. amethystea Thuill. presumably misled by its deep 'amethyst' colour. His identification was disputed and doubted by many yet the name persisted until Pugsley (1940) showed that the continental O. amethystea Thuill. was distinct and that our plant was of an undescribed taxon. Material sent to Beck von Mannagetta had been returned with various unsatisfactory names; Pugsley thus named the plant. Many British botanists since have questioned the distinctness of this taxon. Webb & Chater (1972) sink it completely in O. minor but note that it may have affinities with O. loricata Reichenb. We prefer to treat this taxon as a variety of O. minor. The morphological features distinguishing it are small and continuously variable to O. minor var. minor; this intergradation is most apparent at the eastern extremity of its range, however it has a distinct ecology and distribution and quite marked host specificity. Whereas O. minor var. minor is possibly not truly native, var. maritima would seem to be. Its distribution pattern (Fig. 17) closely reflects that of its chief host, the coastal ecotype of the carrot, Daucus carota subsp. gummifer, and is shared to varying degrees by a range of species including: Lotus subbiflorus, L. angustissimus, Centaurium capitatum, Bromus hordeaceus subsp. ferronii, Polycarpon tetraphyllum and Brassica oleracea, only the last named being of questionable status. The extra-British distribution ofvar. maritima is unclear. In his original description, Pugsley (1940) cited a specimen from Gibraltar but we know of no other records and have seen no material. This taxon, as O. maritima, was included in the Red Data Book (Perring & Farrell, 1983) but only over-collection can affect it and it is somewhat protected from this by the inaccessibility of its haitat