Quick Facts

Quick facts

• Creeping Yellowcress (Rorippa sylvestris) is a perennial herb with yellow flowers that is native to Eurasia and norther Africa.
• It is currently known mainly from bulb farms in South Australia, Tasmania and Victoria from relatively small incursions.
• It poses a threat to mesic ecosystems in the wetter areas of southern Australia including streams, wetlands, and lake margins.
• It has the potential to invade more huge areas of agricultural land It may be more widespread but may have been overlooked due to the similarity with Yellow Cress (Rorippa palustris).

What Does It Look Like?

What is it?

Creeping Yellowcress (Rorippa sylvestris) is a perennial herb with spreading rhizomes (underground horizontal stems). Its stems lie on the ground but are raised at the tips or completely erect. The ribbed stems are usually 15–60 cm tall (but maybe up to 90) cm, hairless or with a few hairs and branched mainly near the base. They are green or becoming purple in strong sun. Leaves at the base of the plant (if present) are stalked, 4–10 cm long (sometimes up to 25 cm) and 2–4 cm wide, with about 6 main divisions per side. Leaves on the stem are similar to the leaves at the base, but smaller, alternating on the stem and stalked. They can be up to 15 cm long and are lobed with margins variously toothed. All the leaves are hairless or have very few short hairs.

The yellow flowers are arranged in loose clusters at the end of the stem and in the angles of the stem leaves have four petals, 4–6 mm across. Fruit set is usually poor.

Fruits are 7–23 mm long and 0.9–1.8 mm wide, and are variable in shape but usually more or less linear, and round to slightly compressed in cross-section. They are hairless and borne at an angle to the stem or are widely spreading. The dark-brown seeds are numerous, 0.6–1 mm long and egg-shaped. (Webb et al. 1988; Rich 1991; Stace 1997)

For further information and assistance with identification of Creeping Yellowcress contact the herbarium in your state or territory.

Flower colour

Yellow

Growth form (weed type/habit)

Herb

Where it currently grows? Preferred habitat

In its natural areas of distribution of Creeping Yellowcress, it occurs along streams, lake and pond margins, swamps and low-lying dam ground, usually favouring more open sites. It is also able to tolerate drought (Tasmanian Land and Water Professionals undated).

In the United Kingdom where it is native it usually grows in mesic sites such moist low ground, riparian ecosystems, lakes and pond margins, swamps wet fields and meadows, usually in barer, more open sites. It also grows on arable land, docks, waste ground and gardens (Rich 1991).

In Tasmania it is so far known mainly from commercial Lilium crops. At Silvan in Victoria it is so far only known from bulb farms as well, the bulbs which like the Tasmanian situation were also sourced from the Netherlands (Eichner 2007, pers. comm.).

Are there similar species?

Rorippa species are variably fertile which often causes problems even identifying them to genus. In Australia there are nine species of Rorippa, and only two species are yellow-flowered, Yellow Cress (R. palustris) and Creeping Yellowcress (R. sylvestris). Unlike Creeping Yellowcress, Yellow Cress is an annual or a biennial, not rhizomatous, has smaller petals and fruit set is usually good. It is likely that Creeping Yellowcress is more widespread in southern Australia than currently recognised, but may have been overlooked due to its similarity with R. palustris (Rich 1991).

Why Is It A Weed?

What are its impacts?

Creeping Yellowcress is one of seventeen sleeper weeds identified by the Bureau of Rural Sciences (following consultation with the Australian Weeds Committee) which could have nationally significant impacts on agriculture if allowed to spread.

Agriculture: While it is currently only known as a horticultural weed it has the potential to invade natural ecosystems, and to impact on other nursery and floriculture enterprises, crops and pastures in the wetter areas of southern Australia. It is considered a threat to all cropping, all grazing and all horticulture in Australia. Based on the modelling, Creeping Yellowcress has the potential to invade more than 650 000 km² of agricultural land, putting at risk millions of dollars in revenue (Cunningham et al. 2004; Cunningham et al. 2006; Tasmanian Land and Water Professionals undated).

It is contains hirsutin in its roots, which inhibits germination and growth of some crops (Yamane et al. 1992).

It is tolerant to both drought and immersion. It has been reported as being a troublesome and persistent weed of nurseries and other horticultural enterprises in Tasmania, where it can have significant impacts on productivity. In the Netherlands it is a common weed of ornamental bulb production areas, where it reduces bulb crop value and marketability as a contaminant of nursery stock. It is also considered a serious agricultural and horticultural weed in the United States where it infests orchards and nurseries (Tasmanian Land and Water Professionals undated).

In New Zealand's south island, it is locally common, in gardens, market gardens, cultivated and swampy land, riverbeds and damp pasture. There it can form dense mats which can completely smother pasture (Webb et al. 1988; Dow AgroSciences undated).

Native ecosystems: In the United States and in New Zealand it invades riparian ecosystems, such as streams and wetlands (Tasmanian Land and Water Professionals undated).

How does it spread?

Creeping Yellowcress generally does not set seed, and reproduction is vegetative only, by the aid of the spreading rhizomes (Webb et al. 1988; Rich 1991). The species generally tends not to readily produce fruit and anecdotal observations indicate this is the case for the Silvan infestations in Victoria (Webb et al. 1988; Rich 1997; Stace 1997; Eichner 2007, pers. comm.).

Creeping Yellowcress has the capacity to readily regenerate from rhizomes, making this the main means of dispersal. It produces numerous new plantlets on small, easily distributed root parts (Koster et al. 1997). It has also been reported to be able to grow roots from leaves floating on a water surface (Wilen 1998).

What is its history in Australia?

Creeping Yellowcress was recorded for Norfolk Island by the botanist Allan Cunningham (Heward 1842) as Nasturtium sylvestre, from 'wet ravines and running streams'. It has apparently not been found on Norfolk Island since, and no specimens of this species have been found among the Allan Cunningham collections examined (Green 1994).

The first definite Australian records are from southern Tasmania, reported from three properties in late 2000 (Cunningham et al. 2004). Field surveys in 2003 detected one population in South Australia of less than 0.5 hectare. While only three infestations covering a total of less than 0.1 hectares were detected in Tasmania there could be many more (Cunningham et al. 2006). In Victoria, the first specimen of creeping yellow cress was collected by AQIS staff in November 2006, from Silvan, in Melbourne's outer east (National Herbarium of Victoria 2007).

Creeping Yellowcress is a common weed in the bulb farms in the Netherlands and it most probably arrived with bulbs contaminated by fragments of rhizomes and possibly also seed (Tasmanian Land and Water Professionals undated).

How To Manage It?

Best practice management

Due to its relatively large root and rhizome system Creeping Yellowcress is difficult to eradicate. If you think that you have found Creeping Yellowcress then you should first contract the biosecurity agency in your state.

Chemical control: It has been difficult to manage with herbicides, but herbicide application remains the main practical means of control. Best results are achieved by applying the herbicide just prior to flowering. Due to the capacity for regeneration from rhizomes follow-up spraying will be required to kill any re-shooting plants and any seedlings (Tasmanian Land and Water Professional undated).

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au

Non-chemical control: Manual control: During any removal by hand, it is important to collect all pieces of rhizomes, as new plants can form from detached rhizomes. As such, machinery shouldn't be used for removal. It is important to avoid transferring plant matter through cultivation and to ensure that all equipment is thoroughly cleaned after being used in contaminated areas (Dow AgroSciences undated, Tasmanian Land and Water Professional undated).

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

Little information is available on the life cycle of Creeping Yellowcress. In New Zealand it flowers between October and March, with most of the flowering between December and February. Fruits are produced from December to March (Webb et al. 1988). In Tasmania flowering has been observed between October and March (Cunningham et al. 2004).

Where Is It Found?

Which states and territories is it found?

SA, TAS, VIC

What areas within states and territories is it found?

In Tasmania Creeping Yellowcress is only known from several ornamental bulb enterprises in southern Tasmania. As yet, it hasn't been recorded outside these bulb farms. The species has also been reported from Aldgate Creek, Mylor, in the Southern Lofty region of South Australia (Cunningham et al. 2006). In Victoria, it is only known from two bulb farms at Silvan (Eichner 2007, pers. comm.).

It has become naturalised in the USA, Canada and Japan (Cunningham et al. 2004).

Where does it originate?

Creeping Yellowcress in native to Europe, West Asia and North Africa (Rich 1991; GRIN 2007).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

TAS, WA

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

YES

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Rorippa sylvestris

Other scientific names (synonyms)?

• Nasturtium sylvestre (L.) W.T.Aiton
• Sisymbrium sylvestre L.

Does it have other known common name(s)?

Creeping Yellow Cress, Yellow Field, Creeping Yellow Fieldcress, Yellow Fieldcress