Elm
tree of the family Ulmaceae (European Hackberry, Elm, Zelkova).

Etymology: of the Latin name ulmus, of Celtic and Indo-European origin; the same root " Al " as in Hawthorn and Alder is found.

Origin: Western Europe, from the Tertiary (65 M of years).
Hardiness: the Smoothleaf Elm is very resistant to cold. it supports cold until -35 °C or -31 °F (zone 4).
Trunk: straight.
Rate of Growth: fast.
Roots: the roots of the elm deeply enter the earth; they often form a pitchfork instead of a tap root, and sometimes two or three.

Varieties: in Europe, Smoothleaf Elm, smooth Elm, mountain Elm; in North America, white Elm of America. They all have:
- a bark smooth in their youth which deeply cracks by maturing, blackish reddish-brown for the Smoothleaf Elm, grey silvery for the mountain Elm,
- a deciduous foliage, leaves in arrangement alternate and distichous. They are asymmetrical at the base (as those of the Hackberry) and double toothed,
- fruits contained in a green membrane (samara) as a pastille - clearly, grouped in bowl, from March-April, before leaves, which gives a characteristic pace to elms.

Legends and traditions: In Greek mythology, tree of Oneiros, God of dreams and of the night, son of Hypnos, God of sleep, himself brother of Thanatos, the demise. Devoted also to Hermes. The winged fruits accompanied souls of the deceaseds owing the supreme judge. In Germania: female blest tree # ash, masculine tree. In The Middle Ages, in the South of France, the justice was held in the shade of an elm. In Celtic astrology, the elm is significant of " generosity ".
The Elm is described in the Encyclopédie ou Dictionnaire raisonné des sciences, des arts et des métiers (written between 1751 and 1772 under the direction of Diderot).

Uses: The wood of the elm is hard and it resists humidity. It is traditionally exploited in framework, hubs of wheels, mills with water, pulleys. The stilts of Venice are in Elm and in Alder. The Elm was widely planted in cities at the time of the king François I^er (16th century) and Henry IV (end of 16th century), undoubtedly because its trunk resists pressure, and because it served for fabricating carriages and cannons. Mary de Médicis introduced the fashion of "courses " planted of trees giving shade as elm: course is the transcription of Italian "Corso", in clearer, in zones of new urbanization (the first is it Courts the Queen, along the Seine, from the castle of Tile factories).
Diseases:
The elm is decimated since 1925 by Dutch elm disease: a mushroom is spread by coleopterans (scolytes) which dig galleries in the wood. Inside these, the mushroom forms its spores, which are then dispersed by the insect. The mushroom also spreads by forms levuroïdes which pass in the sap. It obstructs sap vessels and produces a toxin. The leaves of the tree tan and fall, stems bend down and die, the whole tree droops during years before dying. Its wood is coloured in blackish reddish-brown. Since then, elms are progressively replaced with trees resistant to pollution (Cedrela, Hackberry, wingnut for example).

White elm of America.
Hardiness: zone 6 (it supports cold until -23 °C or -9 °F).
Height: 40 m tall. Flowers in March in 1 cm glomerules. Fruits in March appearing with leaves. They fall in July.