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Knapweed Broomrape

Orobanche elatior

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Plant Profile

Flowering Months:
Orobanchaceae (Broomrape)
Life Cycle:
Maximum Size:
75 centimetres tall
Grassland, roadsides.

Yellow, 2 petals
The densely packed inflorescence is cylindrical and has honey yellow or brownish-yellow, tubular flowers which are reddish or purple-tinged. The flowers are 2-lobed with hairless stamens. The stigmas are yellow. Flowers measure up to 2.5cm (1 inch) across.
The fruit is a capsule.
Knapweed Broomrape does not have any leaves. The stems are upright. Knapweed Broomrape is usually parasitic on Greater Knapweed (Centaurea scabiosa).
Other Names:
Large Broomrape, Tall Broomrape.
Frequency (UK):

Other Information


Orobanche elatior, also known as the tall broomrape or large broomrape, is a species of parasitic plant in the family Orobanchaceae. It is native to Europe and is commonly found in grassland, meadows, and pastures. O. elatior is a rootless plant that derives its nutrients from the roots of other plants, often causing significant damage to the host plant. It has small, yellow or white flowers that bloom in the summer and is known for its ability to survive in dry, nutrient-poor soil. O. elatior is a major agricultural pest in some areas and is difficult to control due to its ability to regenerate from small fragments of its root system. It is particularly problematic for farmers growing vegetables and cereals, as it can reduce crop yields significantly.


Knapweed Broomrape (Orobanche elatior) is a parasitic plant that grows in association with knapweed species in various regions of the world. It is also known as knapweed broomrape, knapweed root parasite, or simply broomrape.

The plant is known for its unusual life cycle as it lacks chlorophyll and depends on other plants for survival. It attaches itself to the roots of knapweed plants and derives its nutrients from them. This makes the knapweed broomrape an interesting subject of study for botanists, ecologists, and agriculturists.

Knapweed broomrape is a native of the Mediterranean region and has spread to other parts of the world, including North America and Australia. It is considered a weed in many of these regions and is often targeted for control and eradication.

The plant has a unique set of adaptations that enable it to effectively parasitize knapweed. For example, it produces specialized structures called haustoria that penetrate the roots of the host plant and extract nutrients from it. Knapweed broomrape also produces chemicals that mimic the host plant's root exudates and attract mycorrhizal fungi, which it then uses to further obtain nutrients from the host plant.

Despite its parasitic nature, knapweed broom rape is not harmful to humans or animals. However, it can have a negative impact on agriculture and ecosystem health by reducing the growth and competitiveness of the host plant. This can lead to decreased plant diversity, altered soil properties, and reduced productivity in affected areas.

Control measures for knapweed broomrape include physical removal, use of herbicides, and cultural practices that favor the growth of non-host plants over the host plants. The use of non-host cover crops and planting of resistant crop varieties are also effective methods for controlling the spread of the parasite.

Another important aspect of knapweed broomrape is its impact on biodiversity. The reduction of the host plant's growth and competitiveness can have cascading effects on the rest of the ecosystem. For example, it can reduce the number and diversity of insect pollinators and herbivores that rely on the host plant for food and habitat. This can in turn affect the populations of higher-level organisms, such as birds and mammals, that feed on insects and herbivores.

In addition, the reduction of plant diversity can alter the functioning of ecosystem processes, such as nutrient cycling and carbon sequestration. This can have negative effects on the overall health and stability of the ecosystem.

It is also worth mentioning that knapweed broom rape is a noxious weed in many regions, and its spread can have significant economic impacts. For example, it can reduce the yields of crops grown in infested fields and increase the costs of control measures. In addition, the presence of the parasite can make it more difficult to control the spread of the knapweed host plant, which is also considered a noxious weed in many regions.

To prevent the spread of knapweed broom rape, it is important to understand its biology and behavior, as well as the impacts it has on ecosystems and agriculture. Effective control measures should be based on an integrated approach that incorporates both chemical and cultural methods. In addition, monitoring and early detection are important for preventing the spread of the parasite to new areas.

In conclusion, knapweed broom rape is a unique and fascinating plant that has important implications for biodiversity, ecosystem health, and agriculture. Understanding its biology and behavior is important for effectively managing and controlling its spread, and maintaining healthy and productive ecosystems.

Distribution Map

Reproduced by kind permission of the BSBI.

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