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An initiative of Earthwatch Institute

  1. Flickr_forestandkimstarr_swampoak_droopingbranchlet Swamp oak drooping branchlet_ForestandKimStarr_Flickr
  2. Flickr_forestandkimstarr_swampoak_coneandfemaleflower Swamp oak cone and female flower_ForestandKimStarr_Flickr
  3. Ala_swampoak_leaves_gregtasney_cc ALA_Swamp oak leaves_GregTasney_CC
  4. Rbg_kwilson_swampoak_bark Swamp oak bark_kWilson_BRG
  5. Flickr_forestandkimstarr_swampoak_flowers Swamp oak flowers_ForestandKimStarr_Flickr
  6. Flickr_dougbeckers_swampoak_prostrateform Swamp oak_prostrate form_DougBeck_Flickr

Swamp She-Oak

Casuarina glauca

Appearance

Short description: Evergreen tree, greyish-brown bark has oak-like appearance, branchlets spreading or drooping. Can be found solo or in dense stands.

Size: Usually 8 – 15 metres high. Can (rarely) reach a maximum of 20 metres high and only reaches 2 metres high on clifftops. The trunk can be up to 35cm in diameter. This tree is also found in prostrate form (lying flat on the ground), reaching 30cm high and 2 metres in width.

Leaves: Segmented branchlets with very small teeth-like leaves (0.6 - 0.9mm long), 12 – 17 leaves arise at the nodes of segments. New growth is strongly recurved (bent or curved backwards or downwards) and become erect as they mature. 

Flowers: This species is dioecious (male and female reproductive structures develop on different individuals). Male inflorescences (arrangement of flowers) are spikes, growing 1.2 – 4cm long with 7-10 whorls per cm (ring of floral parts borne at the same level) and a 0.8mm long anther (pollen-bearing part of the stamen).

Fruits/Seeds: Cylindric, ovular cones are 9-18 mm long and 7-9 mm in diameter are found on a 3-12 mm long stalks. Cones range from rust-coloured to white; they are pubescent (covered with short, soft, erect hairs).

Samaras (dry fruit with wings that do not open) are 3.5 – 6mm long (including the wings).

 

What to Observe

  • First fully open single flower
  • Full flowering (record all days)
  • End of flowering (when 95% f flowers have faded)
  • No flowering
  • Fruiting
  • Seed pods present/absent

ClimateWatch Science Advisor

We expect plants to start shooting and flowering earlier in the year as a result of climate change warming the Earth.  They may start appearing in new areas, as warmer temperatures enable them to live in new environments that were previously too cold for them.  Help scientists answer the question: "How are our animals, plants and ecosystems responding to climate change?"

When To Look

This species is native to coastal regions of New South Wales and Queensland, growing in or near brackish waterways. It is often planted as an ornamental plant, and sometimes for soil stabilisation along creeks, rivers and estuaries. Found in Western Australia, Northern Territory, South Australia, Queensland, New South Wales, Australian Capital Territory and Victoria.

Evergreen tree, although there is a peak in branchlet fall in summer, less in winter. 

August and September see mass flowering of male flowers. Female flowers are less obvious, occurring in small numbers throughout spring. 

In summer, young fruit can be seen and will reach maturity by autumn. Fruit falls more commonly in the winter months.  Cones mature in winter, causing prolific seed fall.

 

Note: ClimateWatch is looking for any changes in the timing of these events, or occurances outside their known ranges, so remember to keep a lookout all year and all regions!

Where To Look

Swamp she-oak distribution map - GBIF

Sightings

References

Clarke, PJ & Allaway, WG, ‘Litterfall in Casuarina glauca coastal wetland forests’, Australian Journal of Botany, vol. 44, no. 4, pp. 373–380, viewed 27 March 2020 

Links

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  1. Did You Know?

    Sheoaks are very unusual plants because they have separate male and female plants. Each year the males will turn a dusky red colour as they release their pollen. The female trees have small red flowers and lots of seed cones.

     

    The sheoak doesn’t have big leaves, instead they have branchlets with different segments. They do have miniature leaves that you can see when you snap a branchlet on one of its joins.

     

    The sheoak is also called a casuarina because their branchlets look very similar to a cassowary feather.

     

    She oak foliage is not made up of leaves, but rather very fine ridged branches or ‘branchlets’. The tiny teeth-like points, which are the true leaves, are at the end of each branchlet. The number of teeth will tell you which species the tree belongs to.

     

    Swamp Oak’s can live to 100-200 years and can regenerate after fire by growing from the root.