This little plant happily invaded a grassy area on dry soil in southeastern MA, Zone 6b, on the coast. The area was mulched with pine wood chips eight or nine years ago and then part of it was used as a parking area while the rest got colonized with grass and other volunteers.

I'd thought it was Waldsteinia fragarioides until I realized that the leaves are five part, not three part.

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The plant spreads by runners.
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The five-petaled flowers emerge from bunches of leaves along the runners.
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What do I have here?

Thanks,
Claire