Can I keep iris bulbs until the spring or should I plant them now?

My aunt has given me a lot of iris bulbs but it's a bit late for potting now (read somewhere that planting time is Aug/Sept.  Is it ok to keep these in a cool dark place (was thinking of the garden shed, wrapped in a paper bag) until the spring?  Or is it ok to plant them now but keep them inside for the winter?

Thanks!

I would plant them now but just add lots of grit. I am a little confused, are these rhizomes? When are you expecting them to flower? Mine are hardy why do they need to go inside?

http://www.gardenersworld.com/how-to/projects/propagating/how-to-divide-iris-rhizomes/169.html

http://www.gardenersworld.com/how-to/projects/planting/how-to-plant-irises/170.html

Whether they are bulbs or rhizomes plant them outside now.

 If they are rhizomes follow instructions here http://mrbrownthumb.blogspot.co.uk/2009/10/how-to-plant-iris-rhizomes-in-your.html

it's a bit late but they are living things and will not survive if you do not plant them now.

If they are iris bulbs/corms (like little daffodil bulbs) plant them now following the instructions here http://www.crocus.co.uk/plants/_/bulbs/other-bulbs/iris-harmony-reticulata/itemno.BU30000721/.  Again, if you keep them they will deteriorate over the winter and die.

It's only a few days past September, the plants can't read the calendar - better late than never in this case - but definitely plant them in the autumn, not the spring.  They need to start growing now and experience the cold winter in order to make them flower in the spring. 

That's great, thanks so much.  What was concerning me is that we've already had frost and I was afraid if I potted them and left them out that the frost would kill them before they'd had a chance to root properly. 

That's my job for today!!