Answer: Check how deeply the water is penetrating by poking a soil probe (any long metal rod or wooden stick) into the soil. It will move easily through moist soil, stopping abruptly where soil is dry. If the soil is really wet to a depth of a foot, I don't think adding more soil on top will make much difference for flower growing. If it is only wet to about 6 inches or so, it could help. Most flower roots grow to a depth of 12 inches. Roots also need oxygen to thrive and in constantly wet soils they don't get any, so they rot. You could plant bog-type plants, that naturally grow in those conditions, or try to do something about the lawn run-off. I wouldn't bother trying to plant other flowers in soil that wet as it will be a losing battle. Another possibility is to plant in containers and set them in this area. Most plants that take wet soil and shade are woodland plants native to other parts of the country. Some of them include baneberry, pearly everlasting, goat's beard, bog rosemary, astilbe, ferns, marsh marigold, sedges, sweet woodruff, japanese iris, bloodroot, and black snakeroot. I hope this info helps.
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