Looks like a Flower Pot Parasol (Leucocoprinus birnbaumii). I occasionally have them coming up in with my houseplants. They don't seem to cause any harm.

Here is a link that might be useful: Fungi in potted plants

Aaron -- Thank you for the response, and I apologize for my delay in sending this.... The link was very helpful and set my mind at ease about the mushrooms. I have had a few more crop up since this post, and I am really enjoying them. They are rather pretty!

So does my capsicum plant!! Can you please tell me whether these mushrooms are poisonous and if so, what implication will this have on my capsicums?

Thanks,

Helena

I have mushrooms in my staghorn, too, but they are brown and ugly. Will read the posted link. Thank you!!