Ulmus glabra Nana - Elm

The Ulmus glabra 'Nana' is a variety of mountain elm that is quite unusual and interesting for its wide and compact habit, which deserves to be highlighted. This small tree has a very slow growth and develops a very dense hemispherical crown. It is also characterised by often bilobed leaves, dark grey bark, a purplish-brown flowering in late winter, light red winged fruits, and foliage that turns yellow in autumn. Very hardy, it thrives in sunny locations with light, moist to wet, even limestone soils.

The Ulmus glabra 'Nana' has an unknown origin, and some sources suggest that it is a witches' broom discovered on a classic mountain elm. It can be found in the French catalog of Simon-Louis from 1869 under the name Ulmus montana 'Nana'. In horticulture, it is not uncommon to find this cultivar called "dwarf Wych elm". The wild mountain elm is found in forests and ravines in the mountains of North America, as well as Western and Central Europe. It can be found up to 1700 m (5577ft) in altitude, in regions with harsh climates, on limestone soils that are moist but well-drained.

The Ulmus glabra 'Nana' reaches, after many years, a height of approximately 5 m (16ft) with a spread of 7 to 8 m (23 to 26ft). Its growth is very slow, estimated at less than 1 m (3ft) in 10-12 years. Its trunk is particularly short, branching very close to the base. The tree has a wide, globular crown supported by short, semi-horizontal branches that bear thick, sinuate twigs. The bark is initially smooth and dark grey, but becomes deeply furrowed over time. The deciduous foliage falls in autumn. The leaves are obovate, measuring 5 to 9 cm (2 to 4in) in length, with doubly dentate margins and a bilobed tip. They are rough and dark green on the upper side, while the lower side is pubescent and lighter green. In autumn, the foliage turns golden yellow and then brown. Flowering occurs in March, before the leaves appear. It consists of small brown to reddish flowers grouped in small clusters on 2-year-old twigs. These are followed by the formation of clusters of winged fruits called samaras, measuring 2 to 5 cm (1 to 2in) in diameter, which turn from green to light red. This elm, with great ornamental value, is susceptible to Dutch elm disease.

The Ulmus glabra 'Nana' can be planted either as a standalone tree or in the centre of a designed bed around it. Its graphic silhouette can be enhanced by a boxwood border, a ground cover with yellow flowers such as Forsythia Marée d'Or, variegated ivy like Hedera algeriensis 'Gloire de Marengo', or even a Trachelospermum jasminoides used as a ground cover, for example.