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.
Sow seed directly outdoors in the fall or plant stratified seed in the spring. Seed of the sugar maple (Acer saccharum) should be stratified for 40 to 90 days at 33 to 41 F, while seed of the Norway maple (Acer platanoides) require 90 to 120 days at 41 F. Plant the seed (fruit) 1/4 to 1 inch deep.