Blue hound's tongue (Cynoglossum creticum)

Blue hound’s tongue is a biennial herb. Its leaves are toxic to livestock, it could cause problems if it becomes established in Australia.

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How does this weed affect you?

Blue hound’s tongue is a biennial herb that has been reported to be a problem weed in Argentina and Chile. It could cause problems if it becomes established in Australia as its leaves are toxic to livestock.

The leaves of blue hound’s tongue contain pyrrolizidine alkaloids that kill cattle and horses. While cattle usually avoid it in the field, the problem occurs when they are fed hay or chopped forage containing the plant. It also hinders the establishment of new pasture. 

What does it look like?

Blue hound’s tongue is a biennial plant which grows up to 600 mm high.

Its stems are densely covered with fine hairs. It has dark-green leaves, up to 200 mm long and 25–35 mm wide, covered with long coarse hairs. The base of the leaf is heart-shaped and clasps the stem. The leaves are alternately placed and decrease in size up the stem.

Blue hound’s tongue has a long taproot which is used to store energy reserves. In the first year of growth, blue hound’s tongue forms a rosette; this is followed by one or more tall flowering stems during the second growing season.

The flower, a 10–11 mm long tube, is pink to blue and has darker hairless veins and stamens growing from the base of the tube. Each flower produces four ‘nutlets’ covered with short, hooked or barbed prickles when mature.

The seeds are oval and 6–8 mm long, and their outer surface is thickly covered with prickles. 

Where is it found?

Blue hounds's tongue was first recorded in Sydney, in 1898. In 1933 a naturalised population was noted in Eden, NSW, and its presence was confirmed until 1976. Two new infestations have been recorded in 2004 upstream from Eden, along the Towamba River.

How does it spread?

Blue hound’s tongue spreads by seeds, mature plants each producing several hundred. The seeds have hooks that attach to clothing and hair very easily, so they can be spread long distances attached to people or animals. Because most seed germinate soon after formation and seed viability is only 2–3 years, there is little development of a soil seedbank. Seedlings are fast growing. In North America, cattle and wildlife are important dispersers of the closely related C. officinale. This is likely also to be the case in Australia, a view supported by the fact that blue hound’s tongue is spreading to upstream areas in NSW. Seeds may be transported by animals or people into disturbed areas where they find suitable conditions for germination.

What type of environment does it grow in?

Blue hound’s tongue is a fairly typical plant of nutrient-rich Mediterranean to warm temperate grassland communities which occur at altitudes of 0–1000 m. It is a native of southern Europe. Information from overseas indicates that blue hound’s tongue most commonly grows on disturbed sites such as road­ sides, sand dunes or open woodlands, where it establishes and spreads quickly. It can tolerate dry conditions.

In North America the closely related C. officinale has been successful in habitats disturbed by logging, grazing and other activities. It depends on the continual creation of these areas and dispersal of seeds to maintain or expand populations. It is most revalent in cool temperate climates with dry summers and a long growing season.

Acknowledgements

Andy Sheppard (CSIRO/Weeds CRC) and John Thorp (National Weeds Management Facilitator). 

References

CRC for Australian Weed Management (2003). Weed Management Guide: Blue hound's tongue. CRC for Australian Weed Management, Adelaide, South Australia.

More information

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Control

Because there are relatively few blue hound’s tongue infestations, and it can potentially be eradicated before it becomes established, any new outbreaks should be reported immediately to your local council weed officer. Do not try to control blue hound’s tongue without their expert assistance. Control effort that is poorly performed or not followed up can actually help spread the weed and worsen the problem. 

Herbicide options

See Using herbicides for more information.

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Glyphosate 360 g/L (Various products)
Rate: 10 mL per 1 L water
Comments: Spot spray. For general weed control in Domestic areas (Home gardens), Commercial, Industrial and Public Service areas, Agricultural buildings and other farm situations.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area	Duty
All of NSW	General Biosecurity Duty All pest plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.

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Reviewed 2021