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Ulmus minor Mill.
Common names: olmo, olma, olmo común, negrillo, álamo negro, llameda, om (catalan), lamaguiro, ulmeiro (galician), zumarr (basque).
The common elm is the tallest species among the three, reaching 25 m like the individual of Somontes in El Pardo, Madrid, or 33 m like the one in the Camino de la Estación in Aranjuez (Madrid). This is also the species that can reach greater trunk girth.
It’s common for samples of this species, especially the ones living in poor conditions, to have corky wings along twigs.
The leaves have a short petiole (5-12 mm), more or less pubescent. The leaf blade has 11 to 14 pairs of secondary veins. The asymmetrical base involves difference of < 7 mm between the two halves. The upper side is coarse in some lineages, smoother in others. On the lower side, there are hairs in the main vein axils and on them.
Flower clusters grow attached to the branchlets. Flowers consist of an external, short, conic, membranaceous, part with 4-8 not deep and ciliate lobes; the male part is made up of 3-5 stamens with exserted, prominent anthers; the female part consists of a pistil with an obovate ovary, a little hairy and very compresses, with two divergent, whitish and very papillate stigmata.
Fruits are initially green and, in full maturity, brownish-yellow. Samaras are 2 cm long, with a glabrous margin and the seed located in the upper half.
Biology and phenology
The sexual maturity is achieved early, generally at 7 years of age. It has a profuse bloom, several weeks after the leaves sprout, very resistant to frosts.
Flowers are cross pollinated by the wind (anemogamous) thus being sensitive to rainfalls, and among different individuals. The period until fertilization is short since fruits are promptly formed.
Fruits are already mature at the beginning of the spring, just after the leaves sprouting, and are quickly scattered, especially in windy days (anemochory). The annual production is regular, but a significant amount of seeds –sometimes even all- are vain, they lack embryo. In natural conditions, seed longevity is very short.
Distribution and ecology
Ulmus minor is a colonizing plant species. Its dispersal strategy is related to the end of winter, thus taking advantage of the opportunity of occupy the lands when the grass layer is not fully emerged or in non-vegetated lands coming from new sediment yields or from soil erosion produced during autumn-winter.
In the Iberian Peninsula, Ulmus minor grows from sea level to 1,500 m (Sierra Nevada). It is hydrophile and likes foodplains and riverbanks, although can live in different sites wherever the soils moisture is high enough during the summer. It grows both in calcareous and in siliceous soils. This elm has a relative large temperature range tolerance, it withstands cold winter and hot summer temperatures, in a similar rate to Quercus ilex.
Its natural areas, especially floodplains, were gradually transformed into agricultural lands since the early Neolithic Age. Although on the other hand, this species was also widely spread because of the value of its wood and other applications. The magnitude of its habitat transformation is so intense that nowadays only a few of natural populations remain. That is why its authoctonous nature was questioned in a recent past, yet this issue has already been settled. Recently, some wood, leaves and pollen fossils have been found, thus confirming its natural condition in the Iberian Peninsula; nevertheless, there is no unanimity of opinion about the extension of its natural distribution. Nowadays it is abundant in the Duero and Tajo basins and the upper parts of Guadiana, Guadalquivir, Ebro and the rest of the great Mediterranean watersheds. It is also present in Mallorca and Menorca islands, becoming rare in Galicia and the Cantabrian basins. In Tenerife it is a feral species.
Its wood was used for producing a variety of pieces (cart axes, kitchen tools, naval construction, etc.), as vineyard stakes, etc. This species has also been used for providing livestock fodder and ornamentally.
This species has also been named as Ulmus campestris and Ulmus procera, although the latter taxon is considered independent by some authors.