Ulmus glabra

Ulmus glabra, the wych elm or Scots elm, has the widest range of the European elm species, from Ireland eastwards to the Ural Mountains, and from the Arctic Circle south to the mountains of the Peloponnese and Sicily, where the species reaches its southern limit in Europe; it is also found in Iran. A large deciduous tree, it is essentially a montane species, growing at altitudes up to 1,500 m (4,900 ft), preferring sites with moist soils and high humidity. The tree can form pure forests in Scandinavia and occurs as far north as latitude 67°N at Beiarn Municipality in Norway. It has been successfully introduced as far north as Tromsø and Alta in northern Norway (70°N). It has also been successfully introduced to Narsarsuaq, near the southern tip of Greenland (61°N).

The tree was by far the most common elm in the north and west of the British Isles and is now acknowledged as the only indisputably British native elm species. Owing to its former abundance in Scotland, the tree was occasionally (primarily historically) known as Scots elm; Loch Lomond is said to be a corruption of the Gaelic Lac Leaman interpreted by some as 'Lake of the Elms', 'leaman' being the genitive plural form of leam or lem, 'elm'.

Closely related species, such as Bergmann's elm U. bergmanniana and Manchurian elm U. laciniata, native to northeast Asia, were once sometimes included in U. glabra; another close relative is the Himalayan or Kashmir elm U. wallichiana. Conversely, Ulmus elliptica from the Caucasus, considered a species by many authorities, is sometimes listed as a regional form of Ulmus glabra.

The word "wych" (also spelled "witch") comes from the Old English wice, meaning pliant or supple, which also gives definition to wicker and weak. Jacob George Strutt's 1822 book, Sylva Britannica attests that the Wych Elm was sometimes referred to as "Wych Hazel", a name now applied to the unrelated genus Hamamelis, commonly called "wych hazels".

Some botanists, notably Lindquist (1931), have proposed two subspecies:

Much overlap is seen between populations with these characters, and the distinction may owe to environmental influence, rather than genetic variation; the subspecies are not accepted by either Flora Europaea or Plants of the World Online.

The type sometimes reaches heights of 40 m (130 ft), typically with a broad crown where open-grown, supported by a short bole up to 2 m (6.6 ft) diameter at breast height (DBH). Normally, root suckers are not seen; natural reproduction is by seed alone. The tree is notable for its very tough, supple young shoots, which are always without the corky ridges or 'wings' characteristic of many elms. The alternate leaves are deciduous, 6–17 cm long by 3–12 cm broad, usually obovate with an asymmetric base, the lobe often completely covering the short (<5 mm) petiole; the upper surface is rough. Leaves on juvenile or shade-grown shoots sometimes have three or more lobes near the apex. The perfect hermaphrodite flowers appear before the leaves in early spring, produced in clusters of 10–20; they are 4 mm across on 10 mm long stems, and being wind-pollinated, are apetalous. The fruit is a winged samara 20 mm long and 15 mm broad, with a single, round, 6 mm seed in the centre, maturing in late spring. The roots can be of extraordinary length: one at Auchencraig, Larg, Ayershire, Scotland has roots which have been traced for a length of 110 metres from the trunk.

While the species is highly susceptible to Dutch elm disease, it is less favoured as a host by the elm bark beetles, which act as vectors. Research in Spain has indicated the presence of a triterpene, alnulin, rendering the tree bark less attractive to the beetle than the field elm, though at 87 μg/g dried bark, its concentration is not as effective as in Ulmus laevis (200 μg/g). Moreover, once the tree is dying, its bark is quickly colonized by the fungus Phoma, which radically reduces the amount of bark available for the beetle to breed on. In European trials, clones of apparently resistant trees were inoculated with the pathogen, causing 85 – 100% wilting, resulting in 68% mortality by the following year. DNA analysis by Cemagref (now Irstea) in France has determined the genetic diversity within the species is very limited, making the chances of a resistant tree evolving rather remote.