Prostanthera eurybioides

Prostanthera eurybioides, commonly known as Monarto mintbush, is a species of flowering plant in the family Lamiaceae and is endemic to the south-east of South Australia. It is a low, spreading shrub with densely hairy branches, thick, elliptic to egg-shaped leaves clustered on short shoots, and violet to mid-purple flowers that are white with orange and dark purple dots inside the petal tube.

Description
Prostanthera eurybioides is a low, spreading shrub that typically grows to less than 1 m high and wide and has more or less cylindrical, densely hairy branches. The leaves are thick, elliptical to egg-shaped, strongly aromatic when crushed, 2–2.5 mm long and 1–2 mm wide, clustered on short shoots and sessile. The flowers are arranged singly in twelve to fourteen leaf axils near the ends of branchlets, each flower on a pedicel 0.5–1.5 mm long. The sepals form a tube 2.5–3 mm long with two lobes, the lower lobe 1.5–3 mm long, the upper lobe 1.5–2 mm long. The petals are 10–12 mm long, form a tube 6–7 mm long, and are violet to mid-purple and white with orange and dark purple dots inside the tube. The lower lip of the petal tube has three lobes, the centre lobe spatula-shaped, 2.5–5 mm long and 4–5 mm wide and the side lobes 4–6 mm long and 3–3.5 mm wide. The upper lip is egg-shaped, 3–6 mm long and 7–12 mm wide with a central notch 0.5–2.5 mm deep. Flowering occurs from September to November.

Taxonomy
Prostanthera eurybioides was first formally described in 1855 by Ferdinand von Mueller in his book Definitions of rare or hitherto undescribed Australian plants.

Distribution and habitat
Monarto mintbush grows amongst granite outcrops in mallee woodland in the Monarto and Mount Monster areas.

Conservation status
This mintbush is classified as "endangered" under the Australian Government Environment Protection and Biodiversity Conservation Act 1999 and the Government of South Australia National Parks and Wildlife Act 1972. The main threats to the species are land clearing, quarry operation at Mount Monster, weed invasion, illegal rubbish dumping, trampling by walkers, and trail bike damage.