Agonis

Agonis species

Synonyms -

Family: Myrtaceae

Names:

Arnica (Agonis marginata)
Swamp Peppermint (Agonis linearifolia)
Wattie (Agonis juniperina)
Willow Myrtle (Agonis flexuosa)

Other Names:

Peppermint (Agonis flexuosa)
Warren River Cedar (Agonis juniperina)

Summary:

Small trees or shrubs with many long thin leaves that smell like peppermint and tend to weep.

Description:

Cotyledons:

Two.

First leaves:

Leaves:

Alternate.
Stipules - None.
Petiole - Short and may be very short and difficult to see.
Blade - Long and slender, dotted with oil glands, smooth edges.

Stems:

Usually has rough, fissured bark.

Flower head:

Usually a globular head at the ends of branches or in axils.

Flowers:

Stalkless. Floral tube is cup shaped.
Ovary - 3 celled with a deep tubular depression around the style. 2-6 erect or ascending ovules per cell
Style - short with a head
Sepals - 5, egg shaped and usually dry and membranous.
Petals - 5, white or pink, longer than sepals, clawed, spreading and persistent. Limb almost circular.
Stamens - Free, shorter than the petals. 10 opposite the petals and sepals or 20-30 mainly opposite the sepals
Anthers - Versatile, open with a lengthwise split. Cells parallel.

Fruit:

Woody capsule, 3 valved. Seed released when ripe.

Seeds:

Tiny.

Roots:

Taproot with many laterals.

Key Characters:

Leaves alternate.
Flowers either in a globular or sessile head or 1-several surrounded by conspicuous involucre bracts hiding the floral tube.
5 Sepals free or joined only near the base.
5 Petals free or joined only near the base.
Stamens shorter than petals.
Ovary 3 celled.
Ovules erect or ascending.
Fruit dehiscent
Adapted from B.L. Rye.

Biology:

Life cycle:

Perennial.

Physiology:

Reproduction:

By seed.
Will regrow from the stump if damaged.

Flowering times:

Mainly spring to early summer.

Seed Biology and Germination:

Flushes of seedling emergence occur. In some years the ground can be carpeted with seedlings, whilst in other years they are relatively rare.

Vegetative Propagules:

Regrows from the stump (coppices).

Hybrids:

None.

Allelopathy:

Leaf litter appears to be strongly allelopathic and few species will establish in litter.

Population Dynamics and Dispersal:

Spread by seed.

Origin and History:

There are about 10 species and all originate in coastal areas of south west WA.

Distribution:

WA.

Agonis baxteri (Benth.) J.R.Wheeler & N.G.Marchant
Courtesy Australia's Virtual Herbarium.

Agonis theiformis Schauer
Courtesy Australia's Virtual Herbarium.

Willow Myrtle (Agonis flexuosa)
Courtesy Australia's Virtual Herbarium.

Agonis undulata Benth.
Courtesy Australia's Virtual Herbarium.

Arnica (Taxandria marginata = Agonis marginata)
Courtesy Australia's Virtual Herbarium.

Swamp Peppermint (Taxandria linearifolia = Agonis linearifolia)
Courtesy Australia's Virtual Herbarium.

Wattie (Taxandria juniperina = Agonis juniperina)
Courtesy Australia's Virtual Herbarium.

Habitats:

Climate:

Temperate Mediterranean.

Soil:

Coastal areas.
Sands to gravel depending on species.

Plant Associations:

Heathland

Significance:

Beneficial:

Honey plant, producing a rather tart, and peppermint flavoured honey.
Ornamental, gums, shelter.

Detrimental:

Fire hazard.
Weed of roadsides, amenity and industrial areas.
Peppermint (Agonis flexuosa) has escaped from a number of gardens and revegetation areas.

Toxicity:

Not recorded as toxic.

Legislation:

The Wildlife Conservation Act prohibits removal of native plants from the wild in their native range on government land.

Management and Control:

Grazing normally provides adequate control after the main stand has been cleared. On roadsides, annual applications of glyphosate effectively prevent invasion.

Thresholds:

Eradication strategies:

Burning followed by bull dosing or chaining is usually the most cost effective for large stands.
Individual trees can be sawn off close to ground level and the stump painted immediately with Access. Basal bark spraying with Access® in diesel is effective. Saplings can be sprayed overall with Garlon, Grazon or glyphosate.

Herbicide resistance:

None reported.

Biological Control:

Unlikely because it is an Australian native species.

Related plants:

Arnica (Agonis marginata)
Strange Peppermint (Agonis grandiflora)
Swamp Peppermint (Agonis linearifolia)
Wattie (Agonis juniperina)
Willow Myrtle or Peppermint (Agonis flexuosa)
Agonis conspicua
Agonis hypericifolia
Agonis linearifolia
Agonis parviceps

Plants of similar appearance:

Willows (Salix spp)

References:

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

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia).

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

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

Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne). #26.1

Marchant et al (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P379-380. Diagrams.

Acknowledgments:

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