Giant sensitive plant

• Shrub that can be erect, prostrate, or climb over vegetation.
• Stems have four-angled, hooked prickles.
• Leaves are alternate, bright green, feathery, fern-like, 10–20cm long.
• Leaves are divided into 5–7 pairs of segments.
• Segments carry about 20 pairs of very small leaflets that close up when disturbed, injured and at nightfall.
• Flowers are round, fluffy, ball-shaped, small, pale-pink, 12mm across.
• Flowers grow on short stalks in leaf joints.
• Seed pods are thorny, clustered, about 25mm long and 6mm wide.
• Seeds are brown, flat, glossy, 2–3mm long.

• Found along roadsides, riverbanks, in cane fields and wet pasture lands.

• Naturalised in high rainfall areas of coastal north Queensland from Ingham to Cooktown and also around Mackay.
• Shires of major infestation: Cassowary Coast, Cook, Cairns, Hinchinbrook, Mackay, Whitsunday and Tablelands.
• Heaviest infestations in Johnstone and Cardwell shires.
• Visit Weeds Australia and click on the distribution tab to access the distribution map.

• Usually flowers and seeds April–June.
• Plants will seed in cold weather April–December.
• Some plants only 10cm tall can set seeds.
• Seeds are retained in spiny pod segments.
• Seeds have been known to lie dormant for up to 50 years.

Economic

• Chokes out cane, other crops and grassland, causing loss of crops and pasture production.

• Seeds spread by flowing water, vehicles, machinery, stock and contaminated earth.

• Find out how farmers can prevent weed spread.
• Find out how gardeners and outdoor enthusiasts can prevent weed spread.

Giant sensitive plant should be treated with herbicide or slashed before seeding occurs as, once a plant seeds, infestations will recur each year for many years.

Mechanical control

• Slash regularly in pastures and non-crop situations to prevent seedlings.
• Cultivate where appropriate, particularly for seedling control.

Herbicide control

• Selective herbicides are available for control of giant sensitive plant in sugar cane.
• Apply herbicides by boom spray fitted with droppers through 110° flat fan nozzles in a volume of 200L of spray solution per hectare as a directional inter-row spray.
• Calculate rate application of residual herbicides depending on size of plant and period of residual control desired.

Read the giant sensitive plant fact sheet (PDF, 2.3MB) for herbicide control and application rates.

Biological control

• Two insects have been released in Queensland but only 1 has successfully established in the field. An indigenous fungus has also exercised some control.
• Giant sensitive plant psyllid Heteropsylla spinulosais a very small sap-feeding bug, about 2.5mm long, pale green and usually found near growing point of plants, either under leaves or on stems. Its 4-week life cycle makes it possible for populations to increase rapidly. In high numbers, it causes growing tip distortion, brittle stems, stunted plants and reduced seed production. It is widespread and travels well via wind. Insect numbers and impact are reduced by flood or drought and availability of plants throughout dry season. Psyllid populations resurge annually from few plants that survive winter.
• Indigenous stem-spot fungus Corynespora cassiicola appears specific to giant sensitive plant and causes defoliation and dieback in very hot humid conditions. It is widespread in Queensland. Initially, older leaflets are shed, then small, dark, oval spots develop along stems. As spotted area increases, growing tip dies. If weather is very hot and humid late in growing season, flowering and seed production can be reduced by stem-spot disease.

• Giant sensitive plant is a category 3 restricted invasive plant under the Biosecurity Act 2014.
• It must not be given away, sold, or released into the environment. Penalties may apply.
• You must take all reasonable and practical measures to minimise the biosecurity risks associated with dealing with giant sensitive plant under your control. This is called a general biosecurity obligation (GBO).
• At a local level, each local government agency must have a biosecurity plan that covers invasive plants in its area. This plan may include actions to be taken on giant sensitive plant. Some of these actions may be required under local laws. Contact your local council for more information.