What Does It Look Like?
What is it?
Mysore Thorn (Caesalpinia decapetala) is a prickly and sprawling shrub or climber that grows to 20 m height. The bark is rough at the base, smoother and cream-green above and the stems are prickly and densely hairy. The leaf stalk is 3–8 cm long and prickly. Each leaf has 4–10 branches that bear 5–12 pairs of oblong to egg shaped hairy leaflets, 7–18 mm long and 2–6 mm wide.
The flowering heads are terminal and 15–35 cm long. The flower petals are almost round, 10–15 mm long and white to pale yellow with the uppermost petal smaller and narrower. The flowers have relatively short stamens (male part of the flower) with whitish or pinkish coloured filaments.
The oblong, brown hairy fruit is 6–10 cm long, 2.3–2.5 cm wide, with a prominent thorn-like straight or gently curved beak and is prominently veined on one side. Inside are 4–9 roundish brown and black seeds (George 1998).
For further information and assistance with identification of Mysore Thorn contact the herbarium in your state or territory.
Growth form (weed type/habit)
Where it currently grows? Preferred habitat
Mysore Thorn grows along road verges and near-coastal creek banks in disturbed forest or woodland, forming large clumps (George 1998), but will also invade pasture (Rolles 2006).
Are there similar species?
Mysore Thorn is very similar to Dwarf Poinciana (Caesalpinia gilliesii), Pride of Barbados (Caesalpinia pulcherrima), Honey Locust (Gleditsia triacanthos) and Parkinsonia (Parkinsonia aculeata).
Mysore Thorn is a prickly plant that has compound leaves bearing several pairs of branchlets. Its pale yellow or whitish-coloured flowers have relatively short stamens (male part of the flower) with whitish or pinkish coloured filaments. The elongated flower clusters are somewhat hairy and the flowers are 10-15 mm long.
While Dwarf Poinciana has compound leaves, each leaf has numerous pairs of branchlets and this species is also distinct from Mysore Thorn by being thornless. It has yellow flowers with very long stamens with distinctive bright red filaments. The elongated flower clusters are covered in sticky hairs and the flowers are 20-25 mm long.
Pride of Barbados is a prickly plant that has compound leaves bearing numerous pairs of branchlets. Its bright yellow, orange and yellow, or red and yellow flowers have very long stamens with yellow or bright red filaments. The elongated flower clusters are hairless and the showy flowers are more than 25 mm long.
Honey Locust is a spiny plant that has compound leaves bearing several pairs of branchlets. Unlike Mysore Thorn it has very small, inconspicuous greenish or creamy-yellow flowers with small hairy stamens.
Parkinsonia (Parkinsonia aculeata) is a spiny plant that has compound leaves bearing a few pairs of long strap-like branchlets. Its bright yellow flowers have relatively short stamens with yellow filaments. The elongated flower clusters are hairless and the flowers are about 10 mm long (Navie 2004).