My weed/wildflower is about 12 to 18 inches tall. Single stem with long slender grass like leaves about 6 - 8 inches long , medium green colour, with with a deep centre vein that cups the leaf into a "V" shape at the stem, and growing from nodes about 1.5 inches apart up the stem. My speciman has 7 leaves. Some of the plants have several of these stems growing in the same cluster, presumably from the same root. On top of the stem is a yellow flower about 2 inches across with 8 slender petals. Inside the flower are some mahogony coloured stamens. Hope someone can help me. I've never seen this before in our area and now have several growing in the long grass behind the shed.