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.
Classified as a slow grower, this small maple will perform best in the dappled shade of its larger counterparts. Japanese maples generally grow at a rate of 12 to 24 inches per season. An average height is 10 to 15 feet in 15 years of growth, with much of their growth coming in earlier years. Most Japanese maples attain a mature height ranging from 10 to 25 feet.