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AN EXCAVATOR was used to dig up a large root system of a Thunbergia weed site in the Whyanbeel Valley.

Douglas Shire Council’s Biosecurity team recently revisited the 2500 square metre site, located on an old private dumpsite.

The crews discovered old tractors and machinery after excavating the site.

Thunbergia is a restricted category three invasive plan under the Biosecurity Act 2014. Council is working with the landholder to control this outbreak.

The vines can climb up to 15 metres and tubers can be as heavy as 70kg.

Council’s Biosecurity Team Leader Bradley Everett said the plant climbs and blankets native vegetation.

“Thunbergia species are a major threat to remnant vegetation in the wet tropics,” he said.

“The weight of the vine can often pull down mature trees.

“Smothered vegetation also has dramatically reduced light levels to lower layers of vegetation, drastically limiting natural growth and killing many native plants.

“Our team has been revisiting old sites with fairly good outcomes until we came across this Thunbergia, which was first treated about 10 years ago.”

Treatment usually involves cutting up the vines and treating the ground tubers with herbicide.

Cutting the vines at ground level will give a smothered tree a reprieve, but regeneration of the vine from tubers will soon occur.

Mr Everett said herbicide treatment would continue for a few years and the crew would check back on the site in about a months’ time.

What does it look like?

  • Blue thunbergia is a vigorous perennial twining vine up climbing up to 15 m if supported.
  • The leaves are opposite along the stem and can be confused with choko vine: up to 15 cm long and 10 cm broad, broad-based narrowing to a pointed tip, usually with deeply scalloped lobes towards the base.
  • The trumpet-shaped flowers have a short, broad tube, white on the outside, yellowish inside, which expands to five rounded, pale lavender-blue petals, one larger than the others.
  • The flowers are up to 8 cm long and 6−8 cm across.
  • The seed pod is inconspicuous, cone shaped, 3−5 cm long, with a rounded base. The seed is flat, up to 1 cm long and covered with brown scales.
  • It is catapulted several meters when the ripe pod splits.
  • The plant develops a very tuberous root system, some tubers being as large as 70 kg. The root system, when cut, persistently sprouts from its many dormant buds.
  • More information available at the Department of Agriculture and Fisheries website.
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