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Creeping yellowcress (Rorippa sylvestris)

In Australia, Creeping yellowcress is known mainly from bulb farms in South Australia, Tasmania and Victoria, but may be more widespread than records show. It could threaten wetlands and other natural ecosystems, as well as agriculture and horticulture in wetter parts of southern Australia.

Key facts

Type: Weed, herb.

Native to: Europe, West Asia and North Africa.

Established in: TAS, SA.

Other names: Creeping Yellow Cress, Yellow Field, Creeping Yellow Fieldcress, Yellow Fieldcress.

Best time to act: Treat just before flowering; flowering has been observed in Tasmania from October to March.

Identification

  • This perennial herb has spreading underground rhizomes and stems that lie along the ground, rise at the tips or grow erect.
  • Its usually hairless, ribbed stems are commonly 15 to 60 cm tall and may reach 90 cm.
  • Leaves are alternate and lobed, with variably toothed margins; they are hairless or have very few short hairs.
  • Loose clusters of yellow flowers have four petals, 4 to 6 mm across.
  • Its narrow, hairless fruits are usually 7 to 23 mm long, and contain numerous dark-brown, egg-shaped seeds.
  • Look-alike: Yellow Cress (Rorippa palustris) is also yellow-flowered, but it is an annual or biennial rather than a rhizomatous perennial, has smaller petals and usually sets fruit well.

Where it grows

In Australia it is known mainly from commercial bulb farms in southern Tasmania and at Silvan in Victoria, and from Aldgate Creek at Mylor in South Australia.

Why it matters

  • It is considered a threat to cropping, grazing and horticulture in Australia, and modelling indicates it could invade more than 650,000 km² of agricultural land.
  • It has been reported as a persistent nursery and horticultural weed in Tasmania, and can reduce the value and marketability of ornamental bulb crops in the Netherlands.
  • Its roots contain hirsutin, which inhibits the germination and growth of some crops.
  • It may invade riparian ecosystems, including streams and wetlands, and has formed dense mats capable of smothering pasture in New Zealand.

How it spreads

  • It generally reproduces vegetatively through spreading rhizomes and usually produces little or no seed.
  • Small pieces of rhizome can regenerate into new plants and are easily distributed; leaves floating on water have also been reported to grow roots.

Control options

  • If you suspect you have found it, contact your state or territory biosecurity agency.
  • Herbicides are the main practical control, and registered herbicides are best applied just before flowering.
  • Follow-up spraying is needed because plants can regrow from rhizomes and seedlings may emerge.
  • For hand removal, collect every piece of rhizome; do not use machinery to remove plants.

Hygiene and washdown

  • Avoid moving plant material through cultivation, and thoroughly clean equipment after using it in an infested area.
  • Take care to collect and contain rhizome fragments, as detached pieces can produce new plants.
  • Inspect and clean vehicles, plant and footwear before leaving an infested area, paying attention to tyres, radiators, belly plates, tracks and floor mats.
  • Wash down at a designated bay where runoff is contained and can be monitored for seedlings.
  • Record each washdown so the client has evidence of clean entry and exit.

Classification by state

  • Australia (national): No national listing. Managed under state and territory law.
  • Queensland: Not prohibited or restricted. Not listed as prohibited or restricted matter in Queensland. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Not a priority weed. Not a state or regional priority weed in NSW. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Not declared. Not declared under the Catchment and Land Protection Act 1994. Other Victorian laws may still apply.
  • South Australia: Not declared. Not declared under the Landscape South Australia Act 2019. Other laws may still apply.
  • Western Australia: Not listed. Not found in the Western Australian Organism List. Check with DPIRD before moving or keeping it.
  • Tasmania: Declared weed. Property managers are required by law to control declared weeds, and their import and sale are prohibited.
  • Northern Territory: Not declared. Not on the NT A to Z weed list, and Weeds Australia does not list it as declared in the NT. Check the NT declared weeds list before moving or planting it.
  • Australian Capital Territory: Not declared. Not declared under the Biosecurity Act 2023 (ACT). A general biosecurity duty still applies.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

  • Tasmania: Biosecurity Act 2019 (Tas), administered by Biosecurity Tasmania
  • South Australia: Landscape South Australia Act 2019 (SA), administered by the regional landscape board

Sources