Answer: First you need to figure out if what you have is truly a wet spot or a vernal pool. Does it dry up later in the season (a vernal pool) or does it continue to be wet throughout the summer?
You say it is "in" your lawn. Are you going to put a bed of plants or shrubs there?
If it's a naturally wet area, such as a spring-fed ditch or a low, wet spot you might consider making a "Bog Garden". You could plant some candelabra primroses, marsh marigolds, astilbes, rheums, ligularias, cinnamon fern and water iris.
If you are not going to add a bed to the lawn and would rather keep it in grass, I would suggest you will need to do some "serious" soil amending. If that's the case, come visit us again "www.garden.org" and perhaps we can help you with that.
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