a similar australian plant (kingia australis).
2. grass tree ·- an australian plant of the genus xanthorrhoea, having a thick trunk crowned with a dense tuft of pendulous, grasslike leaves, from the center of which arises a long stem, bearing at its summit a dense flower spike looking somewhat like a large cat-tail. these plants are often called "blackboys" from the large trunks denuded and blackened by fire. they yield two kinds of fragrant resin, called botany-bay gum, and gum acaroides.