Answer: In the gardening world, almost anything can happen. It is unusual, but occasionally, micro-organisms in mulches can become a nuisance. The shotgun or artillery fungus (Sphaerobolus) may cause problems. While it decays the mulch, it also produces fruiting structures that resemble tiny cream or orange-brown cups that hold a spore mass resembling a tiny black egg (1/10 inch in diameter). This fungus shoots these spore masses high into the air. They stick to any surface and resemble small tar spots on leaves of plants, on cars or on the siding of homes. To avoid damage to cars and houses do not use mulches that contain cellulose (wood). Use pure bark mulches, especially pine, or if the mulch is already in place, cover the hardwood mulch with pine needles. Closer inspection of the leaves may help you determine if the leaves are simply a fungal spot or if your mulch is the culprit.
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