Mine are an annual thing - I buy 100 or so reticulata, poke the bulbs in pots and get rewarded with jewels in February...but then the leaves elongate ridiculously and the bulbs diminish so much that I simply tip the lot into the compost bin and re-order in autumn - they are amazingly cheap. Less keen on histriodes although Katherine Hodgkin has a better rate of return (as also the yellow danfordiae). Have failed to buy any last year (it was the year of little blue bulbs for the wood) so nothing for me this February.

I have had a love/hate thing going on with the winter flowering Algerian iris - when happy against a south facing wall, it is a glorious sight for months on end...but when miserable, it just looks like a ratty bunch of leafage.

In fairness, iris as a genus have rarely floated my boat - I am happy to grow the easy Siberians but have more or less totally abandoned the bearded Germanicas as too wasteful of space and too fleeting in bloom. If I had the damp acidic soil, I would be very tempted by some of the US natives.

Nice pics, Lin - always loved houses which have steps to the front door and the bed with rocks/stones is a favourite scheme of mine too.

I liked the Lousiana iris in a pond (but ducks loved them too....sigh), I have grown the small bulbous iris, and agree, they don't persist...and yes same with Katherine (persisting at least three years). I have the algerian iris as well, and yes, it's wonderful when it blooms, but problematical with the weather each year.

I rather like iris cristata, while the blooms are VERY fleeting, it's delicate and a good ground cover in a small area. It does spread quite rapidly if happy, but it's so small, that it can never get out of control. Who doesn't love flowers that look like this (below...err no above)

I am in zone 8b and reticulata will not return unless I dig them up and store dry until time to plant or if they are in a pot, they need to be placed where they will get no water during the summer.

As for iris cristata, they return but don't multiply very quickly in zone 8b. I have to really watch closely for them because they are planted in shade and are dwarf so they don't stand out like other flowers often do.

I haven't tried Iris histrioides here but don't think they will do much here in this zone.

Yes, bulbs of more northerly species begin to fizzle south of zone 6. You need to look at warmer growing species I guess.

An invaluable book for those of us in the south is Garden Bulbs for the South by Scott Ogden.

Yes, I think I have it (somewhere). Moves...boxes, etc.

Even in the north, I don't find that Iris reticulata multiplies, but it does come back for me. I plant it under the eaves along a southern foundation deeper than recommended for several reasons. It blooms in March, about the only thing other than Hamamelis vernalis that is that early in central NH. The warm foundation helps the early bloom, and the deep planting and dry summer spot help keep it coming back. Being at the back of the garden, I can see the blooms before any other perennials are up, but then the elongating foliage is hidden by perennials as they grow.

Iris cristata does spread for me in a bright shady spot.

Humidity and hot soil will do them in.