This grower is fairly sure of this plant identification.
I have lots of small plants which I split last year they grow quickly and have lovely blue flowers in winter good for dry shade or anywhere else for that matter except very wet ground.
Iris unguicularis (Algerian iris). This is an evergreen beardless species. It will produce its flowers deep down among the clumps of grassy dark green leaves, on stems no more than 20cm long. The flower are pale blue but white and darker blue varieties are also available.
They are fully hardy, but some groups may thrive only in specific growing conditions. All irises are best planted in late summer and early autumn. Outdoors you can grow them in well drained, fertile, neutral or slightly acid or alkaline soil in full sun to lightly dappled shade. In order for irises to thrive, most of them need long, hot summers. Irises that require protection from rain or frost should be grown under glass.
Walls, rock garden. Winter/Spring interest.