Perennials in 9cm pots...Pot on or Plant out?

[IamEarthymama]

As the title really.

I have ordered perennials and shrubs online
They are in 9cm pots

Should I plant them straight out in the borders or would it be better to put them in larger pots for a while?

I have knophia, delphiniums and ceonothus amongst others

I'd pot up the delphiniums, the slugs are extremely partial to them.

I'd pot them up and put them somewhere sheltered for now, it's very chilly at the moment and they won't be used to being in an exposed garden border. Or just leave them in their pots, if they're not too big - I bought some yesterday that 've just put down the side of the greenhouse until I see what the weather is like at the weekend.

Thank you both for replying.
I have potted them up and they are on a cwtched up in a sheltered corner..