Eucalyptus

Eucalyptus species

Family: Myrtaceae

Order: Myrtales

Names:

Eucalyptus is from the Greek eu mean well and kalyptos meaning covered and refers to the cap that covers the stamens in the bud.

Other Names:

Gums because they often produce gum especially when damaged.
Gum Trees.

Summary:

This includes the gum trees from the Eucalyptus genus. They are usually trees up to 40 m tall or mallees up to 10 m tall or shrubs with green, leathery, usually hairless leaves that are usually similar in colour and texture on both sides. There are often oil glands in the leaves. Juvenile leaves are opposite and different to adult leaves which are often alternate or loosely paired. Flowers have a cap that is shed to expose the many stamens. The fruit is usually a woody capsule.

Description:

Cotyledons:

Two.

First leaves:

Usually different to older leaves and opposite for 2-4 pairs, and usually more blue green than older leaves.

Leaves:

Alternate or loosely paired.
Stipules - Usually none.
Petiole - Usually.
Blade - Usually pale to dark green, egg shaped and often curved. Often leathery, aromatic and with oil glands. Usually have a thick vein like the midrib along the edge.

Stems:

Bark smooth and pale to fibrous or flaky and grey to brown. Rough bark when present is usually on main trunk and larger branches. The bark is persistent in the "rough bark" species and shedding in the "smooth bark" species.

Flower head:

Simple axillary umbel or a terminal panicle of umbels with 3-15 or more flowers.

Flowers:

Bisexual. Regular. Stamens form the showy part of the flower.
Ovary - 3-5 celled. half inferior to inferior.
Style - Short.
Stigma - small, terminal.
Sepals - Usually joined into a flower cap (operculum)
Petals - Joined to the sepals or forming a flower cap of their own.
Operculum - conic to hemispheric.
Stamens - Many, in several rows, usually creamy white or sometimes yellow or red. Filament is thread like.
Anthers - Usually attached by the back and versatile.

Fruit:

Woody capsule, 3-5 valved, triangular or awl shaped. Releases seed when ripe. Often bell shaped to conical.

Seeds:

Smooth and glossy rarely winged.

Roots:

Taproot or lignotuber.

Key Characters:

Mature leaves alternate.
Flowers mainly in axillary umbels
Sepals and petals united in the shape of a cap (operculum) which is shed when the bud opens.
Fruit a 3-10 celled capsule
Mainly large trees or mallees.
Adapted from John Black

Biology:

Life cycle:

Perennial. Seeds usually germinate in autumn or spring often with a flush after fire. Saplings usually grow for several years before producing flowers. Some species are very long lived.

Physiology:

Reproduction:

By seed or growth from the lignotuber.

Flowering times:

Very variable and erratic.

Seed Biology and Germination:

Seeds often germinate after fire or smoking.
Sugar Gum seed viability is less than 6 months (Dixon pers comm.)

Vegetative Propagules:

Lignotuber in some species. Many will re shoot or coppice if damaged.

Hybrids:

Many.

Allelopathy:

Population Dynamics and Dispersal:

Spread mainly by seed and intentional planting.

Origin and History:

Mainly Australian natives.

Distribution:

ACT, NSW, NT, QLD, SA, TAS, VIC, WA.

Habitats:

Climate:

Most climates.

Soil:

Most soil types.

Plant Associations:

Significance:

Beneficial:

Valuable source of timber and gums.

Detrimental:

Some species are invasive outside their native range.

Toxicity:

Most have no recorded toxicity.
Sugar Gum (Eucalyptus clodocalyx) and Red Box (Eucalyptus polyanthemos) have been implicated in stock deaths due to cyanide poisoning. Sheep, cattle and goats have been affected.

Symptoms:

Sudden death after eating leaves of suckers or mature trees especially if wilted and between May and September.

Treatment:

As for Cyanide poisoning.
Remove stock from areas where suckers occur or limbs have been brought down by storms or clearing.

Legislation:

None.

Management and Control:

Control introduced species that show a propensity to invade.

Thresholds:

Eradication strategies:

Basal bark application of 1 L of Access® in 60 L of diesel is usually effective.
Cut stump applications of glyphosate or triclopyr are usually effective.
Foliar sprays of metsulfuron, triclopyr or triclopyr plus picloram are usually effective.
Most areas have been controlled by bulldozing, chaining, blade ploughing and burning.
They are relatively tolerant to glyphosate as a foliar spray.

Herbicide resistance:

None reported.

Biological Control:

Unlikely because of the many closely related native species.

Related plants:

Melaleucas
Bottle brushes
Peppermints (Agonis species)

Plants of similar appearance:

Wattles with phyllodes.

References:

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P600. Diagrams.

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

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

Harden, Gwen J. (1991). Flora of NSW. (Royal Botanic Gardens, Sydney). Volume . P76. Diagrams. Photos.

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).

Marchant et al (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P401. Diagram.

McBarron, E.J. (1983). Poisonous plants. (Inkata Press, Melbourne). P135. Diagram.

Acknowledgments:

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