Dutch Iris or Iris reticulata are small bulbs for pots or rockeries.
Flag Iris are big and blousy and grow from Rhizomes.
These pictures of different Iris are grown from bulbs.

The reticulata group produce narrow, triangular leaves and a single, slender bloom per bulb.
Flowers are principally in shades of blue and purple, often with an attractively contrasting orange or yellow mark at the top of the fall.
Iris histrioides ‘George’ is proving to be a good Iris shown top.

Iris Franz Hals above or you could try the unusual Iris ‘Katharine Hodgkin’ below. Its exotic colouring of cream overlaid with a blend of light yellow and greeny-blue comes from its parents.

Read our other article Tips for Growing Spring Iris