KNAPWEED BROOMRAPE

Orobanche elatior

Broomrape Family [Orobanchaceae]

stem

rarity

2nd July 2013, Noar Hill, Hampshire.

Photo: © Dawn Nelson

A stout, upright plant growing up to 75cm high with a long spike of honey-coloured (usually tinged purple) flowers. Totally lacking chlorophyll it is brownish throughout and

parasitic on Greater Knapweed (Centaurea scabiosa) only. The flowers are tubular, curving from upwards to outwards like ship ventilators.

2nd July 2013, Noar Hill, Hampshire.

Photo: © Dawn Nelson

Tapering as it nears the ground this stem seems to defy the normal shape of stems.

2nd July 2013, Noar Hill, Hampshire.

Photo: © Dawn Nelson

A honey-coloured yellowish-brown not dissimilar in colour to that of another saprophyte Yellow Bird's-Nest (Hypopitys monotropa) [was once Monotropa hypopitys!] and to that of the orchid Bird's-Nest Orchid (Neottia nidus-avis) to which it looks more similar.

2nd July 2013, Noar Hill, Hampshire.

Photo: © Dawn Nelson

Here the flowers are tinged purple, as is normal. The tubular flower splays out at the opening in an untidy frilly nature; but there is order here: Although there are only 2 lips, the upper forms a frilly 2-lobed sunshade and the lower is folded into three frilly 'lobes'.
The bracts between the flowers, one per flower, are very narrow, long and brown, several can be seen. Under the hood lurks a stigma with two yellow ovaloid organs at the ends.

2nd July 2013, Noar Hill, Hampshire.

Photo: © Dawn Nelson

The flower has darker veins, some branched. Very short hairs cover the flower.

26th June 2020, Saffron Walden, Essex.

Photo: © Skeeta Crowley

Greater Knapweed is host to Greater Knapweed Broomrape (known just as Knapweed Broomrape - in yellow or browned in the background).

26th June 2020, Saffron Walden, Essex.

Greater Knapweed is the only host to Knapweed Broomrape (no other Knapweeds will do), the leaves of which are shown here with the broomrape right in the middle.

26th June 2020, Saffron Walden, Essex.

A closer view.

Not to be semantically confused with : Broom [a plant with similar name]

Some similarities to : both Ivy Broomrape (Orobanche hederae) and Greater Broomrape (Orobanche rapum-genistae) which are a similar colour, but the former has creamier coloured flowers and is parasitic mainly on Ivy (Hedera Helix) whilst the latter is slightly taller and more butter-coloured parasitising on woody Pea flowers. The best way of differentiating between them is to observe the host plant, but that may be several metres away.

Slight resemblance to : Toothwort (Lathrae squamaria) which is also a chlorophyll-less parasitic plant and is a pale creamy pink and less than half the height at only 30cm.

Superficial resemblance to : Yellow Bird's-Nest (Hypopitys monotropa) but that is also shorter at 30cm and moreover is bent over double at the end like a walking stick.

No relation to : Broom (Cytisus scoparius) or Butcher's Broom (Ruscus aculeatus) [plants with similar name belonging to differing families].

After Common Broomrape (Orobanche minor) this is the next most frequent species. Occupies only the South East of the UK.

Knapweed Broomrape totally lacks chlorophyll and cannot photosynthesis itself, it is totally dependent upon its exclusive parasitic host, Greater Knapweed (Centaurea scabiosa) for nutrition. It's host may be several metres away, connected by the underground root systems, but always on limy soils. All Broomrapes are Parasitic Plants.

See the pull-out table below for comparisons with other Broomrapes and all their identifying and delineating characteristics.

OROBANCHE (BROOMRAPE) COMPARISON TABLE (shrunk)

Orobanche

elatior

⇐ Global Aspect ⇒

Orobanchaceae

Distribution
family8Broomrape family8Orobanchaceae
BSBI maps

Orobanche
(Broomrapes)