Storing extra mulch

Hi all -- I have a mound of shredded bark mulch left over from a new bed planting this past weekend that I don't want to get rid of, but I'm not sure where or how to store it. Right now, I have it piled in a garden cart about the size of a wheelbarrow which is sitting in full sun in my back yard. If I leave it in the cart until I need it, will it get moldy or nasty or will it just continue to break down like mulch does in flower beds? The rest of my property is lawn and I don't really have anyplace I can just dump this stuff. Any suggestions for me? Thanks in advance.
Rhonda Richmond, VA Zone 7
=====================Each of us, a cell of awareness imperfect and incomplete Genetic blends with uncertain ends on a fortune-hunt that's far too fleet

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