Wikijunior:Summer Flowers of Northern New England/Lysimachia quadrifolia
Whorled Loosestrife is a weedy plant that most people would pull up without giving a second thought. But if you see this plant in bloom, take a close look at the flowers. They have five yellow pointed petals making the flower look like a star. At the center of the flower is a tube called a style. It is surrounded by red triangles, one per petal. Each flower grows at the end of a little stem called a petiole (peh-tee-ole) which attaches to the main stem. Lots of things attach to the main stem at this point - not only four (sometimes five) flowers, but usually four (sometimes five) leaves as well. It almost looks like the flowers are there to light up the plant's surroundings, as if they were the light fixtures in a parking lot or at a ball field.