Lawn Weeds

A weed can be loosely defined as ‘a plant out of place’. Thus any plant can be declared a weed if it is growing where it is not wanted.

The best way to keep your lawn weed free is to reduce the ability of weeds to take hold in the first place. The video below has some great tips for keeping your lawn healthy, robust and free from weeds. If all else fails we have a range of weed control products in our online store that are sure to make short work of weeds.

In turf there are generally 2 types of weeds – Broadleaf and Grass Weeds. Below we have described some of the common weed species in Australia.

Grass weeds

Nutgrass

Scientific name

Cyperus rotundus L.

Origin

Cosmopolitan distribution

Description

Perennial sedge with an unjointed solid stem triangular in cross-section. Bright green leaves merge at ground level, tapering to a point. Inflorescence a loose umbel of brown to purple flat, flattened, persistent spikes subtended by 2-4 leaf-like bracts.

Underground, purple, spherical to egg-shaped tubers (‘nuts’) up to 25mm long (usually about 12mm) are formed on rhizomes; ‘nuts’ give rise to new shoots and new rhizomes.

Distribution and Importance

One of the world’s worst weeds, C. rotundus is reported as a weed in more than 90 countries. In Australia the species occurs as a weed in all mainland States. It is a weed of cultivated crops including cotton, maize, sugar cane, tobacco, market gardens as well as orchards and vineyards, and is a particularly tenacious weed in home gardens and parkland on the east coast. The fragrant roots, which are unpleasant to taste, have been used in Eastern perfumes.

The related C. esculentus L., yellow nutgrass, is difficult to distinguish until flowering when it develops a yellowish green inflorescence. It is less widespread and, although a major problem in North America and southern Africa is regarded as a problem in Australia only on the north coast of Qld. Tubers of this species were eaten raw or roasted by the Aborigines. They have also been eaten in Italy.

Another closely related species C. bifax C.B. Clark, Downs nutgrass, which has smaller tubers than C. rotundus, occurs occasionally in western NSW. In western Qld where it is more abundant, especially in the Channel country, it is regarded as useful sheep fodder.

Summergrass

Scientific Name

Digitaria sanguinalis (L.) Scop. Digitaria cilaris

Origin

Cosmopolitan distribution

Description

Called Crabgrass in the United States, there are two species of summer grass in Australia, namely D. ciliaris and D. sanguinalis. The differences between the 2 species are only slight.

The species are distinguished by minute differences including the length of the upper glume (the lower one being minute in both cases); in D. ciliaris the upper glume is greater than half the spikelet length, and in D. sanguinalis the upper glume is less than half the spikelet length.

They germinate when soil temperatures reach 12 to 15°C at 10cm depth. Alternating dry and wet conditions at the soil surface in the spring encourages germination. They germinate and grow best when adequate light and moisture are present.

They compete best with turf when the turf grass is thin and open, mowing height is incorrect and light frequent irrigations are applied. Annuals with fibrous roots and clusters of soft stems which grow close to the ground and may root at the nodes.

Leaves soft and hairy. Inflorescence composed of 3-13 spikes spreading out from a slender erect stem. Spikelets flat, in pairs, with unequal pedicels pressed against 1 side of the rhachis.

Distribution and Importance

D. sanguinalis is a major weed throughout the world in both temperate and tropical crops, although sometimes utilised for grazing. It occurs throughout most of NSW and other States except Qld.

D. ciliaris occurs over much of the same area as D. sanguinalis and also in Qld as a weed in pineapple plantations and orchards. Both species are weeds of gardens, lawns, orchards, cultivation and wasteland.

These species are sometimes confused with Eleusine indica crows foot grass, but this species does not root at the nodes, has hairless leaves, fewer spikes and several florets per spikelet.

Crowsfoot Grass

Scientific name

Eleusine indica (L.) Gaetn

Origin

Cosmopolitan distribution

Description

A tufted, hairless annual up to 0.6m high with a tenacious fibrous root system. Stems upright to sprawling, they may form a mat but do not take root at the nodes. Leaves shiny, green, and smooth. Inflorescence usually up to 5-8 terminal spike-like racemes (4-15cm long) in a digitate arrangement. Spikelets with several florets in 2 rows along 1 side of the digitate branches.

Crowfoot grass germinates when soil temperatures reach 15 to 18°C. This can be approx. 2-3 weeks later than summer grass. It also requires moisture and light for germination. It is very competitive in thin, open turf and turf subject to heavy traffic. It is a most troublesome weed on golf tees, fairways and sporting fields.

Distribution and Importance

E. indica is a major weed in tropical areas of the world, occurring in over 40 crops.

In Australia it occurs in all mainland States and is widespread in NSW. It has been suspected of poisoning stock. In Qld it is a weed of pineapples but in other States is mainly a weed of lawns and gardens.

E. tristachya (Lam.) Lam.., goosegrass, a similar species, is smaller (about 20cm high) and is distinguished by having fewer (2-4) and smaller (1-3 cm) inflorescence branches. It is also a problem in lawns and gardens.

Although sometimes called ‘crab grasses’ these species differ from crabgrass, Digitaria species, in that the latter root at stem nodes, are hairy, have fewer inflorescences and only 2 florets per spikelet.

Paspalum

Scientific name

Paspalum dilatatum poiret

Origin

A native of South America

Description

A tufted perennial grass up to about lm high with short rhizomes. Leaf blades hairless, angled along the midrib. Inflorescence of 3-7 spike-like racemes usually less than 5cm long diverging almost at right angles from the main axis. Spikelets fringed with hairs in 3-4 rows on the underside of a flattened rhachis.

Distribution and Importance

P. dilatatum is widespread in coastal NSW and southern Qld.

It also occurs on the tablelands, slopes and southern plains in NSW, as well as in Vic, SA and WA. Although a useful pasture grass in subtropical coastal areas it is a weed of crops, citrus orchards and lawns. A major world weed, it is a problem in some 28 countries, especially in perennial crops.

P. urvillei Steudel, Vasey grass, a similar but larger species (usually 1-2.5 m high), is distinguished by its longer (up to 12cm) and more numerous (usually 12-20) racemes. It is a weed of the central and north coast of NSW and also occurs in Qld and WA.

P. paniculatum L., Russell River grass another similar species, which occurs on the north coast of NSW and WA, particularly in the north, is about lm high with 20 or more racemes.

Winter Grass

Scientific name

Poa annua L.

Origin

A native of Europe

Description

Winter grass requires a significant amount of light to germinate, and its optimum temperature range for germination is from 10-16°C

An annual or occasionally short-lived perennial up to 0.3m high, often much smaller, with a tufted habit. Leaves light green, soft, with a small (up to 3mm) membranous ligule. Inflorescence an open pyramid-shaped panicle produced just above the leaves, with spikelets of 3 or 4 florets towards the ends of branches; lemmas sparsely hairy.

P/ trivalis L., rough meadow grass, a similar but much rarer species is distinguished by its perennial stoloniferous habit, its longer ligule (4- 10mm), and a tuft of hairs at the base of the lemmas.

Distribution and Importance

P. annua, a cosmopolitan species, is widespread in Australia as a weed of cultivation, lawns and wasteland.

Another perennial somewhat similar to P. annua, P. bulbosa L. is distinguished by its swollen pear shaped leaf bases. It is sometimes found as a pasture weed in central and southern tablelands and slopes of NSW.

Broad Leaf Weeds

Capeweed

Scientific name

Arctotheca calendula (L.) Levyns, Cryptostemma calendula (L.) Druce

Origin

A native of South Africa

Description

A flat stemless or short-stemmed, sprawling annual. Leaves succulent, deeply lobed, covered with down on the lower surface.

Solitary flower heads of yellow ray florets surrounding central blackish purple disc florets. ‘Seeds’ woolly.

Distribution and Importance

A. calendula is a widespread weed of cultivation and pastures occurring in all States. The related A. prostrata (Salisb.) J. Britten, which occurs in Qld and Vic, is prostrate, rooting at stem nodes, and the ‘seeds’ are never densely woolly.

Carrot Weed

Scientific name

Cotula australis (sprengel) J.D. Hook or Common Cotula

Origin

A native of Australia

Description

A small slender herb with carrot-like leaves.

Flower heads terminal, solitary, greenish white, on slender leafless erect peduncles. Stems much branched and trailing, often taking root near the base, then becoming more erect.

Distribution and Importance

C. australis occurs in all States except NT. Widespread and common in moist shady habitats, grasslands, gardens, lawns wasteland.

Bindii

Scientific name

Soliva pterosperma (Juss.) Less. or JO JO (S. sessilis auct. Austr. non Ruiz & Pav.)

Origin

A native of South Africa

Description

A small rosette-forming annual with stolons forming additional rosettes. Leaves finely divided on short petioles. Flower heads slightly convex (not globular), sessile in rosette centres forming burrs with short, sharp spines.

Distribution and Importance

S. pterosperma is principally a weed of lawns and turf familiar to many bare-footed children. It occurs chiefly in eastern areas of NSW as well as Qld, Vic, SA and Tas.

Dandelion

Scientific name

Taraxacum officinale Wiggers s. lat

Origin

A native of Europe

Description

A prostrate, rose-forming, short lived perennial with a thick taproot and containing latex. Leaves deeply divided with the margins irregularly toothed, the tips of each lobe pointing towards the leaf base. Flower heads bright yellow on leafless, hollow peduncles. ‘Seeds’ striped with weak spines near the apex and terminating in a beak (longer than the seed) which bears a pappus of silky white hairs.

Distribution and Importance

T. officinale occurs throughout temperate regions of Australia; more common in the cooler and higher rainfall areas. It is a widespread weed of lawns, roadsides, wasteland and occasionally of cultivation and pastures. The leaves, whilst somewhat bitter are edible as a salad green and the roasted roots are ground for coffee. Suspected of causing hay fever.

Chickweed

Scientific name

Stellaria media (L.) Vill

Origin

A native of Europe; now cosmopolitan

Description

A delicate annual herb with angular stems. Leaves petiolate, ovate with pointed tips. Flowers in leafy terminal cymes, 5 white petals deeply bisected, surrounded by longer hairy sepals.

Distribution and Importance

S. media is a widespread garden weed in southern Australia and regarded as a serious weed in crops in many parts of the world. It is occasionally used as a green vegetable. A less common but similar species, S. pallida (Dumort.) Pire, is distinguished by its lack of petals.

Fathen

Scientific name

Chenopodium album L. or White Goosefoot

Origin

European and Asian or possibly cosmopolitan distribution

Description

A non-aromatic, erect, annual herb. The species varies considerably in stature, colour and leaf shape. Mature plants typically bushy with many branches, ranging from 0 2 to 2m high, usually mealy, especially the flowers and lower leaf surfaces, giving a blue or grey-green appearance.

Leaves ovate or wedge-shaped with coarsely-toothed margins; upper leaves lanceolate and not toothed. Leafy clusters of tiny flowers occur at the end of branches; even very small plants may flower. Seeds shiny, black, horizontally flattened and circular in outline.

Distribution and Importance

C. album is widespread in all states and is a weed of summer crops, winter forage and horticultural crops and is common in home gardens and wasteland. It is one of the most prevalent weeds of cultivation in the warmer regions of the world. Although reported to accumulate oxalate and nitrate, animal deaths due to it are rare. It may cause severe flavour taint in milk if eaten by dairy cows.

Since prehistoric times in Europe and America it has been used as a food plant; leaves of young plants were either boiled or consumed raw. Although largely replaced by spinach after the fifteenth century, it was used during famine conditions in Europe during World War II. Flour from the seeds has been used for baking. The related C. quinoa is used today as a source of flour in the high Andes of South America.

More Information

 

Caution – Absorption of Herbicides Into The Body

When using any herbicide product it is important to ensure it is used appropriately and according to the manufacturers instructions. Always keep chemical out of reach of children and in appropriately labelled containers. For more information on the prevention of poisoning visit the Poisons Information Centre website.

From the records of cases of accidental human poisoning with agricultural chemicals, over 85% have entered the body via skin contact or ‘dermal absorption’. The most common areas of contact with herbicides and pesticides are via the neck, chest and forearm. This is because these parts of the body are the most exposed when handling, mixing and using these chemicals. It is most important to keep these areas covered with protective clothing.

Other parts of the body are also susceptible to absorption, some areas more than others. Below you will find a diagram of a body with relative absorption rates expressed in relation to the forearm which has been given a value of 1.

Relative absorption rates are:

  • Forearm – 1.0
  • Palm of hand – 1.3
  • Ball of foot – 1.6
  • Abdomen – 2.1
  • Scalp – 3.7
  • Forehead – 4.2
  • Ear – 5.4
  • Scrotal area – 11.8

What To Do In An Emergency

In the case of immediate danger and urgent assistance call Emergency 000.

For advice call the Poisons Information Hotline 13 11 26.