Broomrapes & Toothworts
What are they?
Broomrapes and toothworts are mysterious plants; with no sign of any green parts, no stems, leaves or fruits, they emerge each year from the soil, solitarily or in clusters. These members of the Orobanchaceae family are all root parasites, obtaining their essential nutrients by tapping into the subterranean parts of other plants. This means they do not require green parts so remain hidden from view until their flowers emerge. The flowers have all the petals fused into a tube and most species carry them on a single spike.
Where are they found?
The distribution of each species is defined by the availability of the host species. Some are generalists and occur on a number of different species, but most are more particular and a knowledge of the host species and their distribution can help in finding these plants.
Identification
The toothworts are easily identified, but some of the broomrapes are variable and can be tricky. Each flower is accompanied by a pointed bract (and sometimes smaller bracteoles) while beneath the bract, the flower calyx ends in a series of sharply-pointed lobes. The details of the bracts and calyx lobes is important in species confirmation, as is the shape and colour of the lobes of the stigma. As an aid, the close proximity of likely host plants is helpful, too.
Broomrapes could feasibly be confused with Bird's-nest Orchid which can have a superficially similar appearance but which has rather different flowers with six free petals and sepals. Compare also with Yellow Bird's-nest.
Common Broomrape Orobanche minor
Native. Widespread and found on a wide range of host species, especially members of the pea and daisy families. Flowers June to July. A very variable species, perhaps in part due to the wide range of host species parasitised. An increasingly common host is the ornamental Shrubby Ragwort, upon which the broomrape flowers can get to some 60cm tall. Variably pinkish-purple and yellowish in colour. Flowers neatly curved from the base; stigma lobes purplish.
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Ivy Broomrape Orobanche hederae
Native to the UK but only introduced in our region and recorded from two sites in Cambridgeshire and one in Suffolk. Flowers June to August. Parasitises ivy. Similar in overall appearance to Common Broomrape (which may also be found parasitising ivy) but with orange stigma lobes that are close together, not strongly separated.
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Knapweed Broomrape Orobanche elatior
Native. Scarce but sometimes locally common, on chalky soils mostly in the west of the region, but also at a number of sites close to the North Norfolk coast, mirroring the distribution of the host plant. Flowers June to August. Parasitises Greater Knapweed. A relatively tall (to 75cm) and showy species, the whole plant an orange-brown colour; flowers with orange stigma lobes that are close together, not strongly separated.
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Greater Broomrape Orobanche rapum-genistae
Native. Extremely rare and declared extinct in Cambridgeshire in 1913, in Norfolk in 1986 and in Suffolk in 1996. However, a new colony was discovered in northeast Norfolk around 2007, so hope remains that this spectacular species may still be with us. Flowers June to August. Parasitises woody pea plants, especially Gorse and Broom. Flower spikes may grow to nearly a metre tall, the whole plant a reddish-brown colour; flowers with yellow stigma lobes that are well separated.
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Yarrow Broomrape Phelipanche purpurea
Native. A Red Data Book species in the UK. In our region, found at a single site in Suffolk but frequent in a small corner of north-east Norfolk, mostly in clifftop grass. Flowers June to August. Parasitises Yarrow. Flower spikes a peculiar mix of ochre and purple. Differs from our other broomrapes by having an extra pair of bracteoles at the base of each flower, a fact that allows identification of dead stems even in winter.
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Hemp Broomrape Phelipanche ramosa
(Branched Broomrape) Introduced. A widespread species in mainland Europe, growing on a wide variety of hosts. In the UK, it became established for a while as a parasite of Hemp, when that species was grown as a crop in the 19th Century. The last British record was apparently in 1920, but the species may turn up again if Hemp takes off as a viable crop. Flowers probably June to August. Flowers bluish purple with two white patches on the lower part of the corolla. Differs from our native species in often having a branched flower cluster.
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Common Toothwort Lathraea squamaria
Native. Although widespread in the UK, this species has always been rare in East Anglia. The last recorded Cambridgeshire record was in 1954, while there have been no Suffolk records since 1983. Parasitic on several woody plants, most often Hazel, there is always the chance it may be refound in southwest Suffolk as it still occurs not far across the border in northwest Essex. Flowers April to May. Best looked for early in the season as the whitish stems with purple-tipped flowers can get overtopped by stands of Dog's Mercury and Wild Garlic and be harder to spot than might be imagined.
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Purple Toothwort Lathraea clandestina
Introduced. Rare, but seemingly on the increase with new colonies being discovered in recent years. Parasitises willows and poplars. Flowers March to May. Differs from other species of toothwort and broomrape by producing a rounded cluster of flowers that open at ground level, rather than an upright spike.
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