The grey alder (Alnus incana) grows in dry, mesic habitats and is the first tree species to take over unmanaged meadows and fields. Grey alders do not grow very old or tall, and their tops do not curve like those of common alders. Grey alders decay even faster than common alders.
You can find both common and grey alders in Pornaistenniemi, with the former growing by the shore and the latter growing in the inner parts of the cape. The grey alder does not like growing near the sea, due to which it is absent from shore areas and especially islands. The grey alders of Pornaistenniemi are the southernmost grey alders found in Helsinki.