I have a mystery plant in my perennial garden. I found it growing in my lawn previous years, but now it is in my bed. It grows about 30" tall. It looks lily-ish. It has about 4" long by about 2" wide alternate parallel veined medium glossy green leaves. Mid July it was blooming with about 1/2" wide pinkish insides with small green leaves around the blooms (kinda looking like toad lilly blooms) starting about half way up the stalk to the top of the stalk.
Your mystery plant is helleborine (Epipactis helleborine). This orchid is native to Europe, Asia and North Africa and was brought here as a medicinal plant. It can tolerate a variety of conditions but is most often found growing in the shade of trees. It has escaped cultivation and now can be found throughout the eastern half of the United States. Remove this beautiful weed to prevent it from taking over your garden and escaping into our natural areas.