Opuntia monacanthos

Opuntia monacanthos is a succulent spiny cactus growing up to 5 m tall. 
It is often with a clear trunk, much branched with drooping upper branches. 
It spreads rapidly via seed and from broken cladodes, forming impenetrable thicket.

The trunk of Opuntia monacanthos is much branched at the top and has drooping upper branches. 
The stem segments which are called cladodes or pads are thin, flat and narrowly obovate to oblong-lanceolate in shape. 
The margin of the cladode is undulate toward the apex and the base is somewhat cuneate. 
The cladodes are 10 to 35 cm long and 7.5 to 12.5 cm wide. 
They are bright shiny green in colour when young. 
The cladode bears widely spaced areoles which are grey in colour. 
The areoles on the cladodes are with 1 to 3 grey-yellow or red-brown spines with darker tips, while the trunk areoles have 10 or more spines. 
The straight thorns, usually found single, are 3 to 7 cm long. 
 

The leaves of Opuntia monacanthos are simple, succulent and deciduous. 
They are found on new growth only. 
The leaves are dark red or brown in colour and covered with white spots. 
They are lanceolate in shape. They are about 5 mm long. 
hey are growing at the base of the areoles and single thorns.

The flowers of Opuntia monacanthos are yellow to dark yellow in colour. 
They are 7.5 to 10 cm long and 5 to 8 cm across. 
The outer perianth parts are yellow in colour with a reddish median stripe. 
The inner perianth parts are yellow to orange, with green to white staminal filaments. 
The style is green, about 2 cm long. 
The stigma lobes are cream yellow and less than 1 cm long.

The fruit of Opuntia monacanthos is a fleshy thornless pear-like berry. 
It is red-purple in colour at maturity. Its shape is conical to obovoid. 
It is 5 to 7.5 cm long and 4 to 5 cm across. 
The fruits are persistent on the plant and they are edible.