Ulmus 'Densa'

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Ulmus densа is an elm from Central Asia. It was first described from trees growing near Ashkhabad (now Ashgabat) and named Ulmus densa Litv. in 1908. Since then, scientists have debated how it should be classified. Some consider it a separate species, while others see it as a form of Ulmus minor with a very dense crown. In 2020 the Moscow State University herbarium listed Ulmus minor as the accepted name for U. densa Litv.

Taxonomy around U. densa is complex. Litvinov suggested that Ulmus minor 'Umbraculifera'—which has a denser, more rounded crown—was a cultivar of U. densa, naming it U. densa var. bubyriana. Rehder (1949) and Green (1964) treated U. densa as a synonym of 'Umbraculifera'. Flora Iranica (1979) also viewed 'Umbraculifera' as a cultivar of Ulmus minor. In short, different authorities disagree about whether U. densa is a distinct species, a form of U. minor, or linked to the 'Umbraculifera' cultivar.

In appearance, U. densa resembles U. minor but with some differences: it tends to have erect branches and a dense, oblong crown. Leaves are usually smaller, and the branches are smooth and lighter in color. Its compact crown helps the tree conserve moisture, a trait seen in some other drought-tolerant elms.

Habitat and cultivation history show it was widely grown in Turkestan. Locally it is one of several elms called karagach or karagatch (meaning "black tree"). In Western Europe, U. densa Litv. was distributed in the 1930s by Hesse's Nurseries of Weener, Germany.

Natural range overlaps with Ulmus pumila in the mountains of Turkestan, Ferghana, and Aksu, but the extent of any hybridization between the two is not known. Meyer (1912) identified three cultivars of U. densa: 'Stamboul', 'Kitaisky', and 'Seda'.

A large, well-grown specimen grows in Dushanbe Botanic Gardens, Tajikistan (photo from 2019). The gardens also house one of the oldest elm cultivars, 'Umbraculifera', and other elms brought to the West by the Späth nursery of Berlin. The tree or its cultivar form 'Umbraculifera' has been linked to the hybrid Ulmus × androssowii, which involves crossing with Ulmus pumila.