Quick Facts

Quick facts

• Originally from the  Mediterranean region, Lesser Jack (Rumex spinosus) is a low-growing but erect annual herb that grows to 60 cm high with spiny hard fruit.
• A weed of pastures and cultivation and the spiny fruit can cause lameness in stock and domestic and animals especially dogs.
• Occasionally naturalised in southern Australia but is much less common than Spiny Emex.
• Its hardened fruits have much smaller spines than Spiny Emex.
• Also impacts humans, injuring bare feet, and even puncturing thin-soled footwear and bicycle tyres.
• Can be treated by herbicides and physical and mechanical means.

What Does It Look Like?

What is it?

Lesser Jack (Rumex spinosus) is a low-growing annual herb that grows up to 60 cm high, with stems to 80 cm long, upright or lying on or close to the ground. Its leaves are triangular to egg-shaped, 5–12 cm long and 2–8 cm wide, with entire (no teeth or lobes) or undulating margins, and a long petiole (leaf-stalk) 4 -12 cm long, and hairless, and the base of each is surrounded by a membranous sheath.

Flowers are either male or female and occur on the same plant in clusters in the leaf forks. They are inconspicuous and green or whitish. The male flowers are borne in small stalked clusters, while the female flowers are not stalked, spiny and are borne in the leaf forks. 

The fruits are initially green, but turn brown as they mature. They are relatively hard, woody, small fruits are 4–7 mm long,  3–4 mm wide in the lower part, the sides each with a central rib bordered by 2–4 pits on either side, and a horizontal ridge at the widest point, shortly above the base. Three spines on the top of the hard fruit are 1–2 mm long, thick and outward or downward pointing. The plant also produces not very spiny subterranean achenes. Each fruit contains a single seed or nut that is ovate (shaped like a section through the long axis of an egg) to broadly triquetrous (triangular in cross-section, but acutely angled with 3 distinct longitudinal ridges), glossy, brown, and smooth (Navie 2004; Wilson 2007; VicFlora 2016).

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

Flower colour

White, Green

Growth form (weed type/habit)

Herb

Where it currently grows? Preferred habitat

Lesser Jack is found in disturbed areas such as pastures, road verges and wasteland in temperate regions (Western Australian Herbarium 2007; Wilson 2007).

Are there similar species?

Lesser Jack is much less common than the closely related Spiny Emex (Rumex hypogaeus), with which it can hybridise. 

Lesser Jack habit: differs from Spiny Emex and is [more] erect. It also has smaller fruit with shorter spines. Lesser Jack fruits are: 0.4–0.7 cm long and 3–4 mm wide at the top, with spines 1–2 mm long.

Spiny Emex habit: grows close to and along the ground with the end of the branches sometimes erect (not the whole plant erect) with larger fruits. Spiny Emex size are: 0.7–1.1 cm long and, 0.4–0.5 cm wide, with the spines are 2–5 mm long (Wilson 2000; Parsons & Cuthbertson 2001).

Why Is It A Weed?

What are its impacts?

Lesser Jack is a relatively weak competitor but has several strong colonizing characteristics including drought tolerance, rapid growth, abundant seed production, seed dormancy and high dispersal abilities and the two types of achene give the plant its invasive properties. Rapidly produced large subterranean achenes maximise the progeny's fitness/competitiveness whilst numerous (>1000/plant) small spiny aerial achenes maximise the colonizing characteristics of the species. The seeds have the potential to remain viable for many years within the soil enabling the species to persist through long periods of unfavourable conditions (CABI 2021). 

Agriculture: Lesser Jack is a weed of pasture and cultivation, and the spiny fruit can cause lameness in stock. Because it grows taller than Spiny Emex, it is more of a problem in cereal crops than that species (Scott et al. 1996; Wilson 2007). The grain industry (cereals, pulses and oilseeds) has restrictions on the maximum allowable levels of contamination with Rumex seed, from 0 (zero) Rumex seed/500 ml in malt barley in South Australia to 20 Rumex seed/500 ml in feed barley or lupins in Western Australia. In wheat, 8 Rumex seed/500 ml is the national maximum standard (Bowran, 1996). Lesser Jack, with its erect growth habit and a seed size similar to grain makes it potentially a far larger problem to the Australian grain-growing industry than the currently widespread Spiny Emex (CABI 2021).

Native ecosystems: Lesser Jack has the potential to invade in disturbed areas  as a weed in national parks and nature reserves, and marginal sites such as roads, tracks, firebreaks, picnic areas, old homesteads and clearings. It could also impact on biodiversity and the environment by invading natural areas such as the edges of creeks, riverine flats, alluvial flats (claypans, edges of saline lakes) and rocky areas. 

Urban areas: The spiny fruits impact and restrict the use of recreation areas recreational areas, especially where people are bare-footed and spines can penetrate light footwear, and could impact bike riders, puncturing  bicycles tyres (Parsons & Cuthbertson 2001; VicFora 2016). 

How does it spread?

Lesser Jack reproduces by seeds that are readily dispersed after becoming attached to clothing, vehicles and animals. Seeds are also spread in contaminated agricultural produce and by water (Navie 2004).

What is its history in Australia?

It is not known exactly when, where or how Lesser Jack arrived in Australia. It was first noticed about the 1930s in Western Australia. It probably arrived as a contaminant of seed or attached to shoes or equipment. (Weiss & Simmons 1979; Scott et al. 1996; Parsons & Cuthbertson 2001; Wilson 2007).

How To Manage It?

Best practice management

Lesser Jack can be controlled in the same ways as Spiny Emex (Rumex hypogaeus). Control methods include mechanical removal combined with herbicide application. (Scott et al. 1996; Gilbey et al. 1998; Parsons & Cuthbertson 2001; CSIRO Entomology 2006; Western Australian Department of Agriculture and Food undated). The levels of seed dormancy (more than 4 years in some cases) and longevity make Lesser Jack hard to eradicate

Non-chemical control: Small infestations and isolated plants of Lesser Jack can be grubbed out or manually removed. If the plants are seeding then they should be completely destroyed by burning them. 

Small areas should be fenced off to prevent stock, people and vehicles spreading the seed. For large areas infested with Lesser Jack, shallow cultivate in late summer to encourage germination in autumn and then kill the seedlings with cultivation or herbicides. Deep ploughing is not recommended because it buries seed and induces dormancy, which may be broken when the seeds are returned to the surface in following seasons. Any control program must aim at killing all plants shortly after emergence, and needs to be continued for several years (Parsons & Cuthbertson 2001). 'Prickle rollers' have been developed to gather and remove surface Lesser Jack fruit from drying greens in vineyards (Parsons & Cuthbertson 2001).

Chemical control: Cultivation kills seedlings, and can be effective when combined with chemical control (Gilbey et al. 1998; Parsons & Cuthbertson 2001; Land Protection 2006). Herbicides are effective but do not eradicate the problem due to seed bank. Herbicides can be used in agricultural, horticultural, and urban environments for cereal and other crops, pastures and roadside and bushland. 

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

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

Lesser Jack is an annual (a plant that completes its life-cycle and dies within one year) and flowers from late winter through to early summer (Navie 2004).

Where Is It Found?

Which states and territories is it found?

NSW, QLD, SA, VIC, WA

What areas within states and territories is it found?

Lesser Jack is most common in southern Western Australia (but not very common even there), with only a few naturalised populations reported in Queensland, New South Wales, Victoria and South Australia (Weiss & Simmons 1979; Scott et al. 1996). In New South Wales it has been recorded twice in disturbed grazing lands near Gulargambone, but it may not be persistent there (Wilson 2007).

Where does it originate?

Lesser Jack is native to the regions around the Mediterranean (Scott et al. 1996; Wilson 2007).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

Not declared in any states or territories. 

Is it on the National Alert List for Environmental Weeds?

NO

Is it on the Agricultural Sleeper List?

NO

Names And Taxonomy

Main scientific name

Emex spinosa

Other scientific names (synonyms)?

• Emex spinosa var. minor Zohary & Waisel
• Emex spinosa (L.) Campd. var. spinosa
• Rumex spinosus L.

Does it have other known common name(s)?

Doublegee, Erect Emex, Little Jack, Spiny Emex