<Li> The Mergozzo Elm . A four - hundred - year - old Ulmus minor, 5.55 metres in girth, survives in the town of Mergozzo in Piedmont .' L'olmo di Mergozzo', like its French counterparts' l'orme de Biscarosse' and' l'orme de Bettange', is hollowed out by age, its life prolonged by pollarding . </Li> <Li> The "bleeding" elms of Saint Nicholas the Martyr, Thessaly . In the grounds of the Greek Orthodox monastery of Saint Nicholas near Vounaina (Βούναινα), Thessaly, built on the site of the slaughter, c. 720, by maurauding Avars, of the Byzantine ascetic St Nicholas the Martyr (Άγιος Νικόλαος ο εν Βουνένοις) and his followers, stands a group of revered elms that in May on the anniversary of the martyrdom "bleed" a purplish fluid, believed by many of the Orthodox faith to have miraculous healing properties . The phenomenon, possibly related to wetwood, attracts large crowds to the monastery every year . </Li> <Ul> <Li> The Preston Twins in Preston Park, Brighton, England, are the two oldest English elms in the world . Both trees are aged over 400 years and exceed 6 metres in girth . They have been regularly pollarded for many years and both trunks are hollow . The smaller, nearer the A23 London Road, can be entered from the east side; two people can stand comfortably inside it . The trees may be associated with the Medieval Manorial Scrolls kept in the County Records Office in Lewes . </Li> </Ul> <Li> The Preston Twins in Preston Park, Brighton, England, are the two oldest English elms in the world . Both trees are aged over 400 years and exceed 6 metres in girth . They have been regularly pollarded for many years and both trunks are hollow . The smaller, nearer the A23 London Road, can be entered from the east side; two people can stand comfortably inside it . The trees may be associated with the Medieval Manorial Scrolls kept in the County Records Office in Lewes . </Li>

How many types of elm trees are there