The botanical name is Dietes bicolor , common name Yellow Wild Iris. Dietes previously belonged to the Moraea group but was seperated as it has a rhizome rather than a corm like Moraea. The plant naturally occurs near streams and marshy places in the Bathurst district of the Eastern Cape. Though occuring near wet places it is drought hardy (and frost hardy). It grows best in full sun with lots of water and well composted soil though light shade is also ok.
I have found that it needs a lots of water to flower well. Afrikaans people refer to it as as a Rainlily because it often flowers just after good rains. Another name is the Peacock Flower.
You can divide the clumps if it gets too crowded after a few years but it is not really necessary and has a detrimental effect on the plant. It does not need to be cut down each year either. I have found that trimming the plant every so often of all dead or discoloured or straggly leaves and the heavy seed/fruits keeps it looking neat. You should try to find someone with the white wild iris (Dietes grandiflora) and do a trade. The white one has larger flowers , flowers more and is very pretty with its white flower with purple and yellow markings.

Garrick