There are two types of oak native to Ireland. These are Sessile Oak (Dair ghaelach) and Pedunculate Oak (Dair ghailda). These trees can hybridise making it often very difficult to say with confidence at which oak you are looking at! As a loose rule however the Sessile Oak is more likely to be found on poorer soils making it the tree more likely to be found on the upland, western and northern parts of Ireland. The Pedunculate oak by contrast is usually found on better soils. The leaves of both oaks are similar in that they are usually almost oval with between 9-5 deep lopes on either side.