Progesterone. Print | Email article to a friend | Last updated: January 14, 2015. Progesterone is a hormone released by the corpus luteum in the ovary. It plays important roles in the menstrual cycle and in maintaining the early stages of pregnancy. It may also be involved in the growth of certain cancers.
Maple helicopters fall before the leaves drop from the trees. Maple trees (Acer spp.) produce winged seeds called double samaras, which twirl to the ground in late summer or early fall. They resemble helicopters in motion, earning them the common name of helicopters or whirligigs.
The birch seedling tree trunks will start to turn white when the plants are a few years old, but that can vary. Birch trees grow fast, and the Beauty of Birch is a tree you will enjoy for many years. Our favorite is the European White Birch, which has that classic white trunk.