Alder trees are found in all parts of the northern hemisphere and they are often found on poor and/or wet soil. Alders have simple leaves with a toothed edge. The male flowers are in the form of hanging catkins and the female flowers are much smaller catkin-like structures "(see image)." The pollen is transferred from the male to the female flower by the wind. The female flower parts develop into little, green, rounded cone-like fruits which turn brown in autumn and open to release the seeds. 