Small Crumbweed Dysphania pumilio (R. Br.) Mosyakin & Clemants
Synonyms - Chenopodium pumilio
Family: - Chenopodiaceae.
Names:
Chenopodium is from the Neo Latin form of the Greek words Khenopous from khen, a goose, and pous, a foot and refers to the shape of the leaves in some species.
Small Crumbweed - because the leaves have a "mealy" or crumbed appearance.
Other Names:
Boggabri
Clammy Goosefoot
Mintweed
Rough leaved Goosefoot
Summary:
Small Crumbweed (Dysphania pumilio) is a summer growing annual herb to 0.3 m high with a minty odour. It is sometimes erect but often sprawling or ground-hugging. The leaves are elliptic to circular, 3-30 mm long and 2-15 mm wide with a rounded tip, either entire, wavy or with shallow rounded lobes. The upper surface of the leaf is green and the lower surface has both twisted hairs and tiny yellow gland-tipped hairs giving it a mealy appearance. The stems have glandular and segmented hairs on the stems. It forms dense clusters of tiny green flowers which are each 0.5-1 mm across and have 5 floral segments. The stamens are usually reduced to 1 but may be absent in some flowers. The tiny reddish black fruits are held vertically in the whitish floral segments which separate slightly to expose the fruit.
It usually germinates after summer rains and has dense clusters of tiny flowers in autumn and dies off with the onset of cold weather in winter.
Small Crumbweed is a WA native species which is widespread throughout Australia and has become a weed of pastures, gardens and agriculture.
It is often incorrectly called Mintweed or Goosefoot.
Description:
Cotyledons:
Two. Sparse small hairs. Oval. Pointed tip. Base tapered to somewhat squarish. Green on the topside, reddish underneath.
First leaves:
Small hairs. Diamond shaped. Pointed tip. Edges slightly indented or toothed.
Leaves:
Alternate, soft, pale green with whitish mealy appearance.
Petiole - Long and slender. Half as long as the blade, 1.5-10 mm long.
Blade - Variable, oblong, lance, oval or egg-shaped, 3-20 mm long. Green but mealy. May be lobed or with shallow teeth or have wave like indentations on the edges. Sparse simple hairs and sparse short, glandular hairs with resin droplets on the lower surface. Tip rounded. Base tapered.
Stems:
100-800 mm long, prostrate or bending upwards. Longitudinal grooves. Usually with several stems arising or branching from the base. Minty scent. Curved, slender, segmented hairs and short glandular hairs.
Flower head:
Compact globular clusters of 4-9 flowers, in the upper leaf axils or in short panicles that may be up to 300 mm long with long erect slender primary branches. Borne on the ends of branches. Flower clusters shorter than the leaves.
Flowers:
Small, green and in clusters. On almost no stalk or on stalk up to 2mm long. Egg-shaped.
Ovary - Hairless and smooth.
Calyx - 1mm long. Usually white, then, hard and brittle.
Perianth - 5 segments, 1-1.5 mm long, incurved, boat shaped, parallel sided, fused near the base, erect, papery, thin, rounded on the back. Initially green and soft then turns white and brittle when ripe. Tip obtuse. Sparsely hairy near top and on the midrib. Stay together at tops and bottom but open near the middle to expose fruit.
Stamens - 1 or 2. Usually 1.
Anthers -
Fruit:
Globular, 1.5 mm long, dull grey or translucent, sparsely hairy. Falls off the plant easily.
Seeds:
Reddish black, vertical, sometimes keeled.
Roots:
Taproot.
Key Characters:
Perianth segments have a rounded rather than a keeled back. The seed is partially exposed where the white segments don't quite meet in the middle.
Biology:
Life cycle:
Annual or short lived biennial. Seeds germinate in spring and summer.
Physiology:
Reproduction:
By seed.
Flowering times:
Most of the year in SA.
Mainly spring and summer in NSW.
Mainly March to July in Perth.
Seed Biology and Germination:
Vegetative Propagules:
Hybrids:
There appears to be at least 2 forms. One with prostrate stems and almost circular leaves, 3-8 mm long, with shallow rounded lobes or almost no lobes. The other with erect, stouter, much branched stems and egg shaped to oblong leaves 5-20 mm long with obtuse tipped lobes that are quite deep.
Allelopathy:
Produces toxins that can reduce the germination and growth of crop and pasture plants.
Population Dynamics and Dispersal:
Origin and History:
Australia.
Distribution:
ACT, NSW, NT, QLD, SA, TAS, VIC, WA.
Widespread.
Courtesy Australia's Virtual Herbarium
Habitats:
Climate:
Temperate, subtropical and arid regions
Soil:
Red brown soils. Prefers sandy soils.
Less abundant on grey clays.
Plant Associations:
Wide range.
Significance:
Strongly scented like mint.
Beneficial:
Sparingly grazed.
Detrimental:
Weed of pastures, gardens, stubbles and fallows.
Host for Rutherglen bug.
Toxicity:
Toxic to sheep in some conditions. Cattle rarely affected.
Cyanogenetic.
Symptoms:
HCN poisoning.
Sudden death, profuse scouring and gastro-enteritis.
Treatment:
Remove stock from infested areas or provide alternative feed.
Don't expose hungry sheep to infestations.
Treat as for cyanide poisoning.
Legislation:
None.
Management and Control:
Early spraying is required to reduce the effects of the allelopathic chemicals. Mature mintweed that has been killed by herbicides still has significant allelopathy. Toxins are water soluble and disappear a few weeks after the break of the season.
Thresholds:
Eradication strategies:
Hand pull plants after elongation and before seeding in summer. Small Crumbweed is relatively tolerant to low rates of glyphosate. For small areas use 2 L/ha Spray.Seed® plus 2 kg/ha simazine(900g/kg) plus 1% spray oil in early summer for control of existing plants and residual control of seedlings for the season. Wear protective clothing if hand spraying this mix. 500 mL/ha of atrazine(500g/L) plus 1% spray oil provides good control where its use is permitted.
In bushland areas, use 4 L/ha 2,4-DB(400g/L) or 80 mL 2,4-DB plus 25 mL wetting agent in 10 litres of water in early summer on young actively growing plants for reasonably selective control. In areas where hormone herbicides are restricted use 25 g/ha Broadstrike® plus 0.5% Uptake® or 0.5 g Broadstrike® plus 50 mL Uptake® in 10 L water on young plants. A repeat application may be required in years where summer rains induce late germinations.
Even though Small Crumbweed is occasionally toxic, grazing usually provides reasonable control.
It often flourishes in areas that have been overgrazed, disturbed or had poor plant growth during the spring.
Herbicide resistance:
Biological Control:
Grazing with 24 wethers/ha for 2 weeks on a supplement of 150 g/head/day of Lupins or equivalent provides reasonable control of vegetative plants.
Related plants:
Black Crumbweed (C. melanocarpum)
Boggabri (C. carinatum) is almost identical and was often considered to be the same plant up to 1933. In Boggabri weed the perianth segments are more distinctly crested and fully cover the seed. These segments have a hairy hooded wing broadening upwards so that it is more or less triangular in profile.
Crested Goosefoot (C. cristatum)
Desert Goosefoot (C. desertorum ssp. desertorum)
Fat Hen (Chenopodium album) has larger more lobed leaves with dry mealy hairs rather than both twisted and gland-tipped hairs and its doesn't have a minty odour.
Small leaved Goosefoot (C. desertorum ssp. microphyllum)
Stinking Goosefoot (C. vulvaria)
Wormseed (C. ambrosioides var. anthelminticum)
C. curvispicatum
C. detestans
C. erosum
C. opulifolium
(C. polygonoides) Einadia polygonoides
(C. pseudomicrophyllum) C. desertorum ssp. microphyllum
(C. rhadinostachyum) Dysphania rhadinostachya
(C. trigonon) Einadia trigonos
Plants of similar appearance:
References:
Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P149-150. Photo.
Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P289. Diagram.
Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P156.
Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P262. Photo.
Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P148.
Gardner, G.A. and Bennetts, H.W. (1956). The toxic plants of Western Australia. (West Australian Newspapers Ltd, Perth). P24-25.
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). #297.22.
Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P85. Diagram.
