Common ash is the most widely spread ash species in Regional unit Kranj. Flowering ash is less present, while the presence of narrow-leaved ash was notconfirmed in the research. Common ash reaches the highest shares in compartments located near bigger rivers and on lowlands. It grows on moist andfresh sites, on silicate and carbonate grounds. Flowering ash is distinctlya species of dry, southern sites on carbonate grounds. Collected speciments showed considerable variability of leaves by all three species. Forthis reason by ash determination, especially by common and narrow-leaved ash, the consideration of bigger number of signs is necessary. That is why thedetermination keys, which consider a bigger number of signs, are more appropriate for determination of ash species. Common ash is a fast growing tree species, which can with appropriate and timely silviculture grow high quality wood. Therefore the graduation thesis includes some guidelines for silviculture of common ash. Flowering ash is an important tree species of protective forests.