In tree form it has a thickly branched crown and occasionally can reach up to about 20m. The younger branches are reddish-brown in colour and become ash-grey with maturity. Some of the shoots develop red-brown thorns that can be up to 2cm long, and are normally found on the ends of branches. Despite this defence it is less resistant to grazing than other species such as juniper and gorse, whose leaves are also spinose.
The leaves are alternate and deeply lobed; the upper surface is dull green and the lower glaucous. In June hawthorn flowers profusely (Vedel and Lange,1978). Its fruits, known as " haws" give it its name and are consumed by birds aiding its distribution. When closely set it forms an almost impenetrable barrier and combined with its speed of growth it is suitable for hedgerow formation. It is also found in scrub-land and under deciduous woodland where it has a much less dense form and is sometimes coppiced (Tansley, 1939).