ClimateWatch

An initiative of Earthwatch Institute

  1. Xanthorrhoea-australis_davidfrancis34_flickrcc Xanthorrhoea-australis_DavidFrancis34_FlickrCC

Grass-tree

Xanthorrhoea sp

Appearance

Gass-like tree. Trunk resembles a tree above ground or exists under the earth’s surface. Trunk is woody and made up of tiny packed leaves.   

Leaves: clustered in a terminal crown, 30-140 cm long, rhombic (kite-shaped) to wedge-shaped in cross-section, tapering at the ends.   

Flowers: borne as flower clusters on a cylindrical and spike-like woody axis. 

Fruits/Seeds: Fruit case distally pointed, containing 1-2 black seeds.

 

What to Observe

  • Presence
  • Health assessment (see below)
  • First fully open single flower along its flower spike (less than 25% of flowers open)
  • Full flowering (when 50% or more of the spike is in flower)
  • End of flowering (when 95% of the flowers on the spike have faded)
  • Not flowering

Grass Tree Health Assessment (include photos and ‘additional comments’ if necessary). Please submit multiple sightings if more than one photo is required. 

  • ALIVE (A) – Grass Tree foliage is green with lots of fresh growth. Often some browned (not yellow) foliage hanging down over the trunk/base of the plant but extensive healthy growth prevailing. Some individual leaves may show browning or yellowing, but this is not dominant.
  • ALIVE WITH SYMPTOMS (WS) – Grass Tree still has some green foliage. Yellowing or browning (signs of chlorosis) are significant and obvious - possibly some limited fresh new growth. OR, Grass Tree is showing mild signs of browning/yellowing. Note that it is important to distinguish between the naturally forming skirt present on un-burnt grass-trees, which is a natural death of old fronds, and the chlorosis of live fronds. 
  • DEAD (D) – Grass Tree foliage completely brown or absent. Trunk may be decaying, collapsing or a hollow in the ground.

Symptoms of early Phytophthora infection are the same as drought/climate stress symptoms (Connelly; personal communication). Take photos and make assessments to your best ability as long-term monitoring can help identify causes. 

IMPORTANT: Please stay on walking tracks to stop the spread of Phytophthora dieback. Populations of many species of grass-tree have been devastated by Phytophthora cinnamomi, previously known as Cinnamon Fungus. This water mould kills plants by infecting the roots and restricting movement of water and nutrients through the plant tissue. Rotting the roots of grass-trees causes dieback and eventual plant death (see pictures). 
If you do step off the track where grass-trees occur, make sure you always (before and after) brush off any soil material with a stiff brush (e.g. a dish scrubber), and sterilise your boots with a mix of 70% methylated spirits and 30% water. This mix sterilises the tough spores that can lay dormant in the soil where Phytophthora dieback has occurred.
 

*Grass Tree Health Assessment fields adapted from NatureWatch and VNPA Grass Tree Monitoring Instructions, 2016. 

 

ClimateWatch Science Advisor

Plants are expected to alter their shooting and flowering periods as a result of climate change impacting temperature, rainfall and fire regimes. They may also start appearing in new areas, as climate change enables them to live in environments that were previously unsuitable for them. 

Some grass-trees are stimulated by fire, while others are fire-sensitive. Increasing fire events due to climate change may stimulate grass-tree flowering. Fire history can also be determined by the grass-tree’s trunk.

Help scientists answer the question: "How are our animals, plants and ecosystems responding to climate change?"

 

When To Look

Year-round.

Flowering occurs twice to three times each year in mature plants and can occur en masse after a fire.

Note: ClimateWatch is looking for any changes in the timing of these events so remember to keep a lookout all year!

 

Where To Look

Grass-trees are found in all Australian states and territories, especially on the east and west coast. The Austral Grass Tree (X. australis) is one of the most widely distributed species, growing in Tasmania, Victoria, New South Wales, Australian Capital Territory and South Australia. 

If you are able to identify your grass-tree sighting to species level, you can enter these details in ‘additional comments’. Xanthorroea species are sometimes difficult to distinguish from each other. Features which are required include trunk height, ratio of length of spike and leaf colour. 

 Grass Tree distribution map - GBIF

Grass Tree distribution map - GBIF

Sightings

  1. Search Species

  1. What Else?

    Grass-trees without an emergent stem (eg. young Xanthorroea australis and all Xanthorrea minor) are easily confused with Lomandras and other sedges. Grass-tree fronds are not flat (while the sedges are) and don’t grow in a fan-shape.

    Xanthorrhoea is a genus of about 28 species of flowering plants endemic to Australia. Vegetatively, Xanthorroea species are sometimes difficult to distinguish from each other. Features which are required include trunk height, ratio of length of spike and leaf colour. 

    • X. australis has a stem up to 3 m long, often branched. It’s flower spike can be quite long, with its flower-bearing part 110–250 cm long. 
    • X. resinosa has a stem that is absent or up to 0.6 m long and it’s flower-bearing part is shorter than X. australis, 60-120 cm long. At the base of its leaves, X. resinosa produces a yellowish resinous fluid, whereas X. australis produces a red-brown resinous fluid.
    • X. minor (commonly found at Wilson’s Promontory National Park) has a stem that is almost totally subterranean, branched under ground and its flower-bearing part is shorter, 5-30 cm long. 
    • X. glauca found in Central and Northern Victoria can only be reliably distinguished by the longer scape (stem-like flowering stalk of a plant; >65 cm) and pointed to spoon-shaped bracts (modified leaves that surround the flowers). These two species also appear to have different flowering cues – X. glauca regularly flowers in the absence of fire. In contrast, flowering in X. australis is typically restricted to mass events in the year following fire.

    If you are able to identify your grass-tree sighting to species level, you can enter these details in ‘additional comments’. 

     

  1. Did You Know?

    • A reference to its yellow resin, Xanthorrhoea literally means "yellow flow" in Ancient Greek.
    • The common name grass tree is a misnomer: Xanthorrhoea are not grasses, nor are they trees. They are actually distantly related to lilies (Patykowski, J., 2018)
    • Some species provide a resin which was used by Aboriginal people as an adhesive in the manufacture of tools. The stem was also used for the lower part of a spear (Oates & Seeman 1979). In the bush the flowers could reveal directions, since flowers on the warmer, sunnier side – usually north – of the spike often open before the flowers on the cooler side facing away from the sun (Gardening Australia, 2007).
    • Grass-tree can grow for up to 600 years.
    • By examining the size of a grass-tree’s ‘skirt’, we can estimate when a fire last occurred. The grass-tree’s ability to resprout and produce flowers quickly after fire  makes them a vital life-line for animals living in recently-burnt habitat.
    • Populations of many species of grass-tree have been devastated by Phytophthora cinnamomi, previously known as Cinnamon Fungus (a misnomer)