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.
There are 13 species of maple trees native to North America. Some are naturally fast-growing, while others grow slowly. If you want your maple tree to grow fast, you should start with a fast-growing species. Silver maples grow faster than any other maple, but red maples are fast-growing, too. Both species are considered moderately short-lived, with a life expectancy of around 150 years. Once you have your tree, you can do several things to stimulate growth. Red maples are a fairly fast-growing species of maple.