Fairly normal on home made compost. Either ignore it or take of the top centimetre and replace with grit or gravel.

You are aware that your platycodon will disppear under the soil and reappear quite late on next spring, I hope?

No, I didn't! It's in a pot by the way, if that helps.. thankyou you two,( I thought it had got the lurgy!)

Does it have to be in a pot? It means that your pot will apear to be empty for several months!

this mould also appears if the compost is too wet. is the pot raised up off the ground a 1/2 " or so to help it drain? I'd pop some winter bedding in your pot too. :o)

Well I only bought it recently and didn't know much about it, so I didn't know if it would be ok outside during the winter, Spritz. And as I only have a small garden, with minimal flower beds, I tend to have most things in pots, and just keep upsizing them as they grow bigger. the plants not the pots.. As for the compost being wet, it might have been, cos it was outside in really heavy rain for a few days. Is winter bedding what they also call mulch? I'll do that Seaburn ...(Istill know so little!.. but there is SO MUCH to learn about gardening.. )

No - Sbg means plants like pansies/violas/primulas etc.

Mulch is when you pile compost around a plant's roots to help it survive, or spread it across the flowerbeds to feed the soil.

Hope that helps, Mazzie. :-))