I'm developing a fondness for simple-flowered irises.
I don't have any, but I've been admiring them. They're usually a clear blue to purple color, and seem to form robust clumps, flowering seemingly without fuss in spring.
That's my kind of perennial.
They don't seem to fit my 'working for a living' screen for our garden, as they seem to be a horticultural selection of a native species from elsewhere in the world. But, to be fair, our native irises aren't exactly a wildlife magnet, either. Maybe that's their strategy!
This iris near the Geology Museum was photographed in dim light, so isn't as vibrantly colored as it actually is.