Some sort of fungus living on the decaying organic matter. Not a problem. Just don’t let the baby eat the compost. 😉 (For our American readers .... for compost read ‘medium’)

Hard to see but perhaps the early stages of bird’s nest fungus. If so, it’s harmless.

tj

use your compost in the garden.. and use proper media for seed starting ...

and going one step further.. sterilize your seedlings media to avoid bugs.. shrooms.. etc.. in your pots ... especially if they are coming indoors ...

its easier to avoid problems.. than cure them ..

and to be clear .... this is not a problem.. they are continuing the decomposition process ... breaking down other materials.. which might be a fancy way of saying your compost wasnt fully finished ... for this use anyway ...

ken

https://tipnut.com/sterilize-soil/

Thanks for the advice. I'd have used proper media if we were able to get something decent locally but a bit stuck where we are and the stuff we could get delivered was either out of our budget or couldn't get delivered here.

Would also have kept it all outside of we could but greenhouse still hasn't arrived and it's been snowing.

Didn't know sterilising soil was a thing.

Abi, don’t worry. I’ve never sterilised sowing or planting compost and never had any problems. And I’ve grown plenty of things in my home made compost. One can’t always get to a garden centre when one wants to. I’m guessing you’re in the U.K. where we say compost for both compost and media.

What are are you growing? This spring is cold and I’ve barely sown anything yet. Plenty of time still.

Thank you. Very reassuring. Yes, uk based. I've pushed my sowing a bit later than usual. Mainly due to seeds arriving late and a bit of hectic life with a new baby. Currently sown dwarf beans, broad beans, nasturtium, cherry tomatoes, salad tomatoes, marigold, strawberries, two types of lettuce, curly kale, Cavolo nero, everlasting sweet peas, calendula, peppers, Aubergine, onions, spaghetti squash and courgettes.

Buy a water meter. Usually, mushroom growth is a sign of overwatering. The mushrooms won't cause problems, but the overwatering will.

Thank you. They're all indoor sown and will start to harden off the broad beans after the weekend as the weather looks to be getting a bit better.

I'm not overly fond of runner beans so have left them out this year but maybe next year.

I was a bit over zealous with the water just after I planted because of the change in weather (I sowed them during the hot Easter weekend so did a good bit of watering as they were getting dry quickly). I've cut right back this week though.

Thank you again!