Plant them now as they are often good to go before they darken and harden. That is according to Gail Harland who wrote the HPS book on Paeonies.

Should I put them in a pot or in the ground? How do they need to be treated? Why am I so ignorant?

not ignorant at all, why should anyone know everything. I had to ask for help when I first grew them from seed. Totally new to me then. Do you know which plant they have come from [ie colour of flower]

I put them singularly in a 9cm pot about half way down the pot and then cover with compost to the top. Keep them out side and water if very dry. They will appear to do nothing next year but they will, if they germinate, produce a long root. the second year they will produce a leaf.

They will also do just as well in the ground. I have seedlings of the yellow one growing where they have dropped into the garden.

I have seedlings of the yellow one if you'd like to give one/two a home.

Thanks Eileen, very helpful! I've never grown paeonies - how big to the tree ones grow please? That's a very kind offer - am tempted but not sure where I'd put one Would the little yellow ones need planting out now or could they stay in a pot for now? I would love a bit of advice before plunging in. And could they put up with what can sometimes be a very windy site? Will try to remember to discover what colour the seeds came from.

I keep my yellow one topped t 6ft as I prune it when it gets too big.

They can stay in a pot for years and be in a big ornamental pot if you didn't want it in the ground.

I suspect they would be ok in a windy site. Happy to send you one to try and if it doesnt survive then not to worry.