This is commonly known as Artillery Fungus (Sphaerobolus stellatus). This a wood rotting fungus that can grow in your mulch. It literally shoots spores out from the mulch up to 20 feet and sticks to your siding, car anything else that in the area.
How do you prevent? We suggest to freshen(raking) the mulch a couple times a year. Add a thin lay of mulch about 1-2 years. Keep downspouts from pooling water in the mulch. See Youtube video for more suggestions:
How do I remove it from my siding? Once the spores shoot out and stick to your sidling it becomes very tough to remove. We suggest hiring a professional to come out and clean it. Check out the hyperlink below for many more suggestions!