What Is Sweet Vernal Grass: Learn About Sweet Vernal In Landscapes

What Is Sweet Vernal Grass: Learn About Sweet Vernal In Landscapes

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The aromatic scent of sweet vernal grass (Anthoxanthum odoratum) makes it an excellent choice for dried flower arrangements or potpourri. But because of its aggressive nature, you have to be careful how you grow it.

What is Sweet Vernal Grass?

Sweet vernal is a small, 2-foot (60 cm.) tall, cool season perennial grass. It grows best in sun to light shade. It is sometimes referred to as vanilla grass because of the aroma emitted when it is cut – the smell of fresh hay with a hint of vanilla. This sweet, fresh hay smell comes from the substance coumarin, also found in sweet woodruff.

Sweet vernal plants flower earlier than most other grasses, from early to mid-spring, with dense yellow clusters which are a favorite food plant for the larvae of brown and skipper butterflies. Despite some safety concerns, one of the sweet vernal uses is as an ingredient in medicines for headache, nausea and sleeplessness.

Sweet Vernal in Landscapes

Sweet vernal is common in meadows, pastures and other grasslands. In the wild, it seeds readily and the seeds can be widely dispersed by wind, water and vehicles.

In many regions, it is considered to be invasive because it can take over a grassland area in a relatively short period of time. In facts, because it does well in poor land conditions and the seed is cheap and abundant, another of the sweet vernal uses is in the roughs on golf courses.

Controlling Sweet Vernal Grass

Because of its aggressive spreading nature, however, it is best to grow sweet vernal plants in containers rather than directly in garden beds. Even if grown in containers, there is a risk of the plant spreading to unwanted areas.

If you want to prevent the spread of seeds in your yard or garden, do not allow the sweet vernal plant to flower and seed. If you decide to let some seed heads remain and you end up with a few unwanted plants, the roots are shallow enough where the sweet vernal plants can be pulled up by hand or dug up with a hoe.

With the proper care and maintenance, you can effectively control the growth of these plants, which will allow you to enjoy them in your dried arrangements.

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What Is Sweet Vernal Grass: Learn About Sweet Vernal In Landscapes - garden

Sweet Vernal Grass
Anthoxanthum odoratum L.

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

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.

The leaf blade is rolled in the bud.
The leaves have a bitter taste with a smell like newly mown hay.
Blade - Flat, green, 15-300 mm long x 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.

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 x 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 a short underground rhizome that is occasionally up to 200 mm long.

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.

Perennial grass. Seed germinates in autumn and forms 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.

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:

It 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.

Population Dynamics and Dispersal:

Spread mainly by intentional planting or seed in hay, fodder or other produce. It is also spread by water, wind and in soil or on animals or slashers and other machinery.

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.

Courtesy Australia's Virtual Herbarium.

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.

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.

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 produced by 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.

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.

Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P35, Photo.

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). Pt 1, P163. Diagram.

Blood, K. (2001). Environmental weeds: a field guide for SE Australia. (CH Jerram & Associates, Australia). P190. Photos.

Bodkin, F. (1986). Encyclopaedia Botanica. (Angus and Robertson, Australia).

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P62. Diagram P61.

Ciba Geigy (1981) Grass Weeds 2. CIBA GEIGY Ltd, Basle, Switzerland. P16. Diagrams.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney).

Gardner, C.A. (1951) The Flora of Western Australia. Vol 1. Part 1. Gramineae. P28. Diagram.

Harden, Gwen J. (1991). Flora of NSW. (Royal Botanic Gardens, Sydney). Volume . P634. Diagram.

Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P42, Photo.

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

Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne). #75.1.

Marchant et al (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P939.

Muyt, A. (2001). Bush Invaders of South-East Australia: a guide to the identification and control of environmental weeds found in South East Australia. (R.G and F.J. Richardson, Australia). P52-53. Photos.

Paczkowska, G. and Chapman, A. (2000). The Western Australia flora: a descriptive catalogue. (Wildflower Society of Western Australia (Inc), the Western Australian Herbarium, CALM and the Botanic Gardens & Parks Authority). P95.

Paterson, J.G. (1977). Grasses in South Western Australia. (Western Australian Department of Agriculture Bulletin 4007). P23.

Wheeler, Judy, Marchant, Neville and Lewington, Margaret. (2002). Flora of the South West: Bunbury - Augusta - Denmark. (Western Australian Herbarium, Bentley, Western Australia). P399.

How to make żubrówka

Good spirits . a glass of John Wright's homemade meadowsweet grass vodka, mixed with juice from apples in his garden. Photograph: John Wright

Good spirits . a glass of John Wright's homemade meadowsweet grass vodka, mixed with juice from apples in his garden. Photograph: John Wright

I 've never had much to do with vodka. It famously doesn't taste of anything, and because I was a cabinet maker for 30 years the smell always reminds me of hard work. I can tell you with some authority that vodka and French polish are barely distinguishable by smell alone, except that French polish is the sweeter. I suspect that neat vodka is, like Marmite, something one has to be born to. For most of us, it needs to be mixed or flavoured.

A couple of weeks ago, my friend Susanne sent me a particularly intriguing parcel containing a small piece of grass, complete with roots, a packet of seeds, a small bottle of slightly coloured liquid with a leaf in it and list of instructions. The bottle contained a vodka-based grass infusion called żubrówka and the remaining contents were the wherewithal to make it myself. I've planted the grass and have the seeds in the freezer – apparently an aid to germination. But being an impatient fellow, I've been exploring other ways of making the stuff.

The species Susanne sent me is bison grass. The Latin name, Hierochloe odorata, means "sweet-smelling holy grass", from its being strewn around church doorways on saints' days. It does exist wild in the UK but only in isolated locations in Scotland, so I started to look for alternatives. The aromatic compound in bison grass is called coumarin. It has a vanilla-like odour familiar to many as the smell of newly mown hay. This gave a clue as to where I might look: hay-meadows. Sweet vernal grass is the main originator of this smell as it too contains coumarin. I'm terrible at identifying grasses and a root through Kingcombe meadows nature reserve – a place very familiar to me from the fungus forays I lead there every year – produced nothing.

Undaunted, I looked to other plants. I knew that meadowsweet contained coumarin, but it's rather late in the season for this plant. Nevertheless, I managed to find several in flower and duly collected some blossoms. Another group of plants containing coumarin are the bedstraws. Chief among these is woodruff, but lady's bedstraw is a more accessible plant, common in many hedgerows. A long walk – followed, after my back started complaining, by a suspicious-looking hedgerow kerb-crawl – produced nothing except hedge bedstraw, which doesn't smell of anything nice at all. Lady's bedstraw was in high flower until very recently and I eventually found some growing near the pavement on someone's lawn. I consider things to be fair foraging game if you can reach them from a public right of way, so I grabbed a handful and took it home.

Lady's bedstraw. Photo: John Wright

The wonderful smell of lady's bedstraw (not as sickly as meadowsweet) becomes stronger with drying. When you dry it, do so carefully – mould can convert the coumarin to a toxic compound. In fact, I should say more toxic, as coumarin itself is a poison – though, assuming you are in good health, it'll only harm you in considerably larger doses than you could obtain from our present project and over a longish period of time. It is, however, seriously poisonous to rats, being a chemical precursor of warfarin, so if you're a rat don't go near the stuff.

As in the manufacture of true bison-grass żubrówka, infuse your chosen plant for a few days in vodka until, as Susanne puts it, the mixture turns the colour of a healthy mid-stream urine sample, then remove all plant material and bottle the liquor. I suggest filling the jar loosely one half full of dried plant, perhaps less for the more potent meadowsweet. If you have some bison grass then half a dozen leaves the full length of a litre bottle will do the trick. When the brewing is finished, remove them all from the żubrówka save one, which is left for decoration. Having completed my experiments I must say that, despite my misgivings, meadowsweet came out on top, tasting remarkably like Susanne's brew. "Sickly" is evidently best.

Neat shots of any of these vodka-based drinks are a little too much for me, but a mix with apple juice is both traditional and open to another foraging enterprise. Crabapples and wildings (hedgerow apple trees that have grown from discarded pips) are just coming into ripeness now. Use a juicer or a press, add sugar (they can be incredibly tart) and mix with ice and your żubrówka to taste. The result is highly refreshing drink with a complex flavour that will have people puzzling over what you've handed them.

Finally, I have it on authority that a hangover from vodka can be avoided by eating small pieces of lard as you drink. I think I'd rather have the hangover.

Learning to Grow Sweet Grass the Hard Way

Sweet grass has long been considered a sacred plant for a variety of different cultures. One whiff of this aromatic beauty, and you’re certain to know why. It has a distinctive scent that you’ll never forget. It’s a fairly hardy perennial, and it’s as native to North America as it is to Europe. It reaches just 20 cm in height at its peak, but the leaves can stretch outward for quite a ways by the end of the growing season.

Traditional uses abound for this amazing plant. It was often used as incense, tea flavoring, a kind of tobacco, and even perfume. It was, and is, also used for basket making.

As phenomenal as it is, it’s actually harder than you may think to grow. Unless you already have a plant established, it can be fairly difficult to get some started in your yard. Only a fresh seed will actually germinate with this plant. I learned that bit the hard way. I purchased seeds for nearly two years straight, and they were almost always dead. I simply couldn’t get it to grow through a store-bought seed. The only way I could really get it going was by dividing my plants. It seems to take really well to that.

One year, I decided to try something a bit different – fresh seeds. I created an open flat of soil right next to my plants, then started splitting them open right over the soil. In what seems like mere minutes in my memory, I had created a new sweet grass plant.

Sweet grass has long had a close association with people, which is probably one reason why viable seeds are so hard to get these days. Like garlic and horseradish, humans tend to replant it everywhere, and nature has a way of knowing when to scale back on viable seed production.

There are few things quite as rewarding as sweet grass, though, so spend a bit of time experimenting with this very traditional plant on your own this season.


Management Research Programs:

Research burns were conducted in 1986 and 1987 at Willow Creek Preserve, OR. Additional research burns were done at Cascade Head Preserve, OR, in 1988. It is still too early to evaluate the results of these burns on the control of sweet vernal grass. [26] For further information contact: Cathy Macdonald, Land Steward The Nature Conservancy Oregon Field Office 1205 NW 25th Avenue Portland, OR 97210 (503) 228-9561

Management Research Needs:

Very little research has been done on controlling sweet vernal grass. Much research needs to be done in the areas of biological control, prescribed burning, and mechanical removal techniques.

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