Muskweed

Myagrum perfoliatum L.

Family: - Brassicaceae.

Names:

Myagrum is from the Greek myagros, which was the name of an early Brassica plant.
Perfoliatum is from the Latin per meaning through and folium meaning leaf and refers to the appearance of the stems passing through the clasping leaves.
Muskweed of unknown origin and peculiar because the plant has no significant odour.

Other names:

Mitre Cress (UK)
Round Island Spinach in NSW.

Summary:

An erect, many branched annual plant with yellow flowers and flattened, wedge shaped pods with a conical tip that are held at 30 degrees to the stem.

Description:

Cotyledons:

Two. Club shaped . Short stalk. Hairless. Tip slightly indented. Sides convex. Base tapered. Surface hairless. Incumbent.

First leaves:

Club shaped. Tip Round. Edges lobed. Hairless.

Leaves:

Form a basal rosette to 450 mm diameter that usually sits very close to the ground.
Petiole - None.
Blade - Blue green with white veins, irregularly lobed or toothed and embrace the stem with 2 auricles. Tip round. Hairless.
Stem leaves - Alternate, blue green, oblong to lance shaped, stem clasping with 2 auricles. Tip pointed. Edges may be smooth of finely toothed. Base tapered. Surface hairless.

Stems:

Blue green, slender, erect, up to 1000 mm. Branching at base and along its length. Many branched. Hairless and smooth.

Flower head:

Long, many flowered raceme, borne near the tops of stems.

Flowers:

Pale yellow, small, 5-10 mm wide on short stalks.
Ovary - 2 ovules. Short, persistent, conical style.
Sepals - Almost erect.
Petals - 4, yellow, spoon shaped.
Stamens -
Anthers -

Fruit:

Hard, horny, erect, wedge shaped, flattened and wrinkled seed capsule or pod, 5-7 mm long by 4-5 mm wide, with a conical style on top. Pod doesn't open to release the seed. The upper part has 2 swollen, empty cells. The lower part has an egg shaped cell with one pendulous seed.
Sticks out from stem on a small, thick stalk.

Seeds:

Brown, egg shaped, smooth, 2 mm long.

Roots:

Simple taproot.

Key Characters:

Yellow flowers. Wedge shaped, hard pods held at an acute angle to the stem.

Biology:

Life cycle:

Annual. Germinates from autumn to spring. Grows through winter and spring. Flowers from July to October, sets seed set from mid August to early December and dies in summer.

Physiology:

Resistant to Blackleg and may be a useful source of genes (559).

Reproduction:

By seed. Probably about 1000 seeds per plant.

Flowering times:

Spring.
July to mid October in the eastern states.

Seed Biology and Germination:

Many seeds are shed before harvest and remain dormant in the soil for 2-3 years but may survive in the soil for up to 6 to 8 years.
Pod is confers some dormancy as most seed germinates when removed from the pod.
Germinates at temperatures of 4-29 deg C.
Most plants emerge from the top 5 cm of soil.
(560) has seed biology data.
Soil seed banks up to 3000/m2.

Vegetative Propagules:

None.

Hybrids:

Allelopathy:

Population Dynamics and Dispersal:

Spread by seed.
Spread as a contaminant of cereal and other grain. The pod is similar in size to wheat and difficult to separate.
Seed is also spread by dry plants tumbling in the wind.
Greatest populations establish in wet years after an early break.
Generally has a staggered germination from April to October.

Origin and History:

Southern Europe. Mediterranean. Western Asia.
First noticed in the Victorian Wimmera region around 1900 and by 1915 large areas were infested.
First recorded in SA in 1925 and was initially troublesome but declined for unknown reasons then once again became a problem as hormone herbicides were used to control other Brassica weeds. Widespread on the Yorke Peninsula.
Found in NSW in 1999 (561) near Quirindi on the Liverpool Plains.

Distribution:

QLD, SA, VIC, NSW
Italy, Lebanon, Turkey, USA.

Courtesy Australia's Virtual Herbarium.

Habitats:

Climate:

Temperate.

Soil:

Occurs on dry, exposed, light and heavy soils.
Prefers alkaline clay-loam and clay soils.

Plant Associations:

Significance:

Beneficial:

Oil can be extracted from Muskweed (562).
Resistant to Blackleg (559) and low in glucosinolates (563) so it may be a useful source of genes for Brassica crops.

Detrimental:

Weed of crops causing yield reductions due to competition and interferes with harvesting by tangling into a ball in front of the harvester comb.
Major weed of barley, canola, chickpeas, cereals, field peas, faba beans, lentils, lucerne, lupins, oats, wheat.
Contaminates canola, pulse and cereal grain and is difficult to clean from cereals because it is similar in size to the cereal grains.
Weed of pastures, cultivated land and disturbed areas.

Toxicity:

Not recorded as toxic.

Legislation:

Noxious weed of Victoria.

Management and Control:

Cultivation effectively controls seedlings but must be repeated regularly for several years.
Graze pastures heavily in spring to reduce seed set.
Crop infested areas after cultivation with late sown wheat, planted at a high rate, and use chlorsulfuron as a pre emergent herbicide.
Shorter fallows, continuous cropping and broad-leaved crops in the rotation favour Muskweed

Thresholds:

Yield losses of 50% recorded in chickpeas and lentils.
In canola and cereals it also causes significant yield losses.

Eradication strategies:

Treat small areas with 2 L/ha Tordon 75-D plus 500 mL/ha diflufenican500 whenever plants appear. For spot spraying, mix 50 mL Tordon 75-D plus 10 mL diflufenican500 in 10 L water and spray until just wet. Remove plants with seed and burn them or soak in diesel.

Herbicide resistance:

None recorded.

Biological Control:

Related plants:

Brassica species but no other Myagrum species in Australia.

Plants of similar appearance:

Radish, turnip and mustards all have heart shaped cotyledons when young and green leaves whereas Muskweed has club shaped cotyledons and leaves with white veins.
New Zealand Spinach (Tetragonia tetragonoides)
Prickly lettuce (Lactuca serriola) at the seedling and bolting stages.
Sowthistle (Sonchus oleraceus) is similar at the seedling stage.
Turnip weed (Rapistrum rugosum) looks similar when in pod but the pods are distinctly different on closer inspection.
Willow lettuce (Lactuca saligna) at the seedling and bolting stages.

References:

Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P135. Photo.

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P382, 387. Diagram of flower.

Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).

Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #854.1.

Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). P346-347. Photos.

Wilding, J.L. et al. (1987). Crop weeds. (Inkata Press, Melbourne). P81. Diagrams. Photos.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.