Sweet Vernal Grass

Anthoxanthum odoratum L.

Synonyms -

Family: - Poaceae


Anthoxanthum is derived from the Greek anthos meaning flower and xanthos meaning yellow and referring to the yellow green of the panicle after flowering.

Other Names

Scented Vernal Grass

Spring Grass

Sweet Vernalgrass


A sweetly fragrant, tufted perennial grass with green to golden brown, compact, cylindrical seed heads. The tussock of leaves is usually about 25 cm high and wide with many simple stems about 50 cm tall holding the seed heads well above the leaves.




First leaves:


The leaf blade is rolled in the bud.

The leaves have a bitter taste with a smell like newly mown hay.
Blade - Flat, 15-300 mm long by 2-9 mm wide, parallel sided or occasionally somewhat lance shaped. The mid vein is obvious on the underside. The upper side is usually hairy, the underside rarely hairy and the margins are hairless. Maybe slightly rough to touch. It is always hairy around the collar. Tip pointed.
Ligule - Membranous, flat topped (truncate), 1-5 mm long, often slightly torn.
Auricles - are replaced by hairs.
Sheath - Rounded on the back. Often hairy on the lower leaves. Hairless on the margins.

Stem leaves - Smaller than basal leaves.


Flower stem - Erect, slender, unbranched, smooth, 100-1000 mm tall. Usually has many stems. The nodes and stem are hairless. Sometimes slightly kneed at the nodes. The nodes are swollen.

Flower head:

Dense, cylindrical oblong to narrowly egg shaped, spike like panicle, 10-120 mm long that is slightly expanded at flowering and sometimes discontinuous near the base. Green to golden brown at flowering.


Spikelets - Single, oblong to narrowly egg shaped, 6-10 mm long by 2 mm wide, silky. Flattened and crowded on short stalks (pedicels) with 3 florets. Disarticulates (breaks) above the glumes.
Florets - 3. Lower two are sterile and flattened and the upper one bisexual.
Glumes - Persistent, translucent with a green keel, egg shaped, stiff, dry and chaffy (scarious) with conspicuous green nerves. First (lower) glume, 1 nerved, about 3-4.5 mm long or half as long as the second (upper). Upper glume is keeled, 7-10 mm long, 3 nerved and about as long as the spikelet and enfolds the florets. Pointed tip. Sparsely hairy to hairless. Both glumes longer than the lemmas.
Palea - One ribbed. As long as the lemma.
Lemma - First lemma is 2-4 mm long, golden hairy, 5-7 nerved empty, truncate or bilobed and has a short, rough (scabrid) awn, 2-4 mm long arising from the middle of its back. The second lemma is 2-3.5 mm long, golden hairy, 5-7 nerved, empty, truncate or bilobed and has a bent awn that is 6-9 mm long or about as long as the spikelet and arises from the base of the lemma. Fertile third lemma is shorter (2-3 mm long and hidden by the sterile lemmas), hairless, shiny brown, circular to elliptic, awnless and translucent with golden anthers showing through.
Stamens - 2 in bisexual upper floret.
Anthers - golden



Brown, egg shaped, slightly flattened, 2-3 mm long.


Shallow and fibrous. It sometimes has short underground rhizomes that is occasionally up to 200 mm long.

Key Characters:

Compact spike like panicle.

Disarticulates above the persistent glumes.

Spikelets subsessile to shortly pedicellate.

Spikelets with 2 sterile and a fertile, bisexual floret.

Sterile lemmas below the fertile lemma..

Sterile lemmas longer than the fertile lemma, hairy and with a dorsal awn.

Glumes thin and membranous, anthers commonly visible through the tissue.

Glumes keeled and not winged.

Lower glume half as long as the upper glume.

Glumes as long or longer than the florets

Glumes as long or longer than the sterile lemmas.

Adapted from Black, Burbidge and Gray, Gardner & Marchant et al.


Life cycle:

Perennial grass. Seedling germinate in autumn and form a small tussock by spring. Most of the top growth dies off over summer and new leaves emerge in autumn. It flowers in spring. In good conditions it forms a short underground rhizome over time to increase the size of the tussock.


Frost and drought tolerant.

Low nutritive value.

The odour is due to its coumarin content.

Allelopathic or produces chemicals that reduce the growth of companion plants.

Bitter taste.


By seed and rhizomes.

Flowering times:

Spring to summer in NSW.

Mainly September to January in Victoria.

October to January in SA.

Late spring to early summer in WA with odd plants flowering as early as June in WA. November to January in Perth with some flowers from September.

Seed Biology and Germination:

May produce more than 1250 seeds per plant. Most seed germinates with a year or two but some appears to remain dormant for several years.

Vegetative Propagules:

Short underground rhizome.



It is allelopathic.

Population Dynamics and Dispersal:

Spread mainly by seed in water, wind and soil or on animals or slashers and other machinery.

Origin and History:

It comes from Europe and temperate Asia.

It was planted at low levels in pasture paddocks to provide a sweet odour in hay or arrived as a contaminant of fodder.



It is recorded in the Esperance, Jarrah Forest, Swan and Warren regions of the South West of WA.

Argentina, Britain, Canada, Columbia, Chile, China, Europe, Hawaii, Iberian Peninsula, India, Italy, France, Japan, Middle East, New Zealand, Northern Africa, Southern Africa, USA, USSR


Tolerates trampling and full sun to light shade. It is quite tolerant of dense native vegetation especially in wet areas.


Temperate to alpine in areas receiving more than 600 mm rainfall annually.


Occurs on a wide range of soils. Often more troublesome on low potash or low fertility soils, white sands and black sandy loams.

Plant Associations:


Relatively common weed of high rainfall areas.


Fodder but not very palatable.


Used in herbal medicine.


Weed of disturbed areas, roadsides, pastures, gardens, dry coastal and riparian areas, heathland, woodland, grassland, dry and damp sclerophyll forests, cool temperate rainforests, alpine and sub-alpine areas and seasonal freshwater wetlands.

It can be quite invasive and compete with relatively undisturbed scrub species.

It releases chemicals that reduce the growth of companion species.


Contains coumarin which produces the scent.

Generally not toxic unless it is a major part of the diet or is a major component of hay or silage. In pastures stock tend to avoid eating it.




Listed as a "Garden thug".

Management and Control:

Generally fairly easy to remove by scalping as the root system is shallow. Ensure all rhizomes are removed as these will regrow. Material removed should be burnt to destroy seeds and rhizomes.

Burning with a hot fire helps control shallow rhizomes and seeds.

Burning in spring may allow easier treatment of regrowth with herbicides.

Grass selective sprays from the Fop group provide good control.

In pastures - plant competitive perennial grasses, mow in spring before seed set or spray top with paraquat and correct any nutrient deficiencies.

If replanting bush or pasture into dense infestations, try to remove as much of the top growth as possible by collection, burning or cultivation well before planting to reduce the effects of allelopathic chemicals in the plant.


Eradication strategies:

In bushland areas:

Spray with a herbicide from the Fop group in winter before seed set and repeat annually until no more plants appear.

In agricultural situations:

Plant and fertilize a broad leaved crop or pasture and apply a herbicide from the Fop group in winter for at least 2 seasons. Replant perennial grasses the season after the last Sweet Vernal Grass plants are found.

Herbicide resistance:

None reported.

Biological Control:

Related plants:

No other plants in this genus in WA.

Annual Vernal Grass (Anthoxanthum aristatum) occurs in the Victoria. It is similar but smaller and is an annual.

Plants of similar appearance:

Holygrass (Heirochloe species) is an eastern states native grass that has the same coumarin scent.

Marram Grass (Ammophila arenaria) has a similar seed head but occurs on coastal sand dunes.

Phalaris species have a similar seed head but has no awns in the spikelet and has winged glumes.

Plume Grass (Dichelachne species) is a native grass.

Reed Bentgrass (Deyeuxia quadriseta) is a native grass.

Weeping Grass (Microlaena stipoides) is a native grass.


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