Celtis australis

Celtis australis in Europe: distribution, habitat, usage and threats

D. Magni, G. Caudullo Celtis australis L., commonly known as southern nettle tree or European hackberry, is native in South Europe from the Mediterranean Basin to Asia Minor. It prefers sunny exposures in thermophile mixed deciduous forests, well adapted to rocky soils lacking in humus, where it is able to crush rocks entering their fissures with its strong roots. Thanks to its frugality, this tree is used for afforestation in difficult terrains against erosion. It is also an ornamental tree because of its dome-shaped crown. During the last 50 years nettle tree has been showing decline symptoms especially in urban areas due to a combination of climate change effects and the action of different pathogens. The nettle tree, or European hackberry, (Celtis australis

L.) is a deciduous tree which usually grows 15-20 m in height, Frequency only exceptionally reaching 25-30 m1. Its shape appears as < 25% 25% - 50% 2 a low dome, with a wide, regular, dense, light green crown . 50% - 75% The trunk is vertical, robust and enlarging at the bottom with > 75% Chorology 3 age, with girth of 3 m, exceptionally up to 6 m . The bark is Native thin, grey or pale brown, and smooth, with horizontal wrinkles similar to beech; sometimes becoming more rugged with warty excrescences in old age2-4. The leaves are simple, from 5 to 15 cm long, usually wavy, alternate, lanceolate or oval- lanceolate, serrate with regular jagged teeth (except near the base), acuminate or twisted apex, and cuneate or rounded slightly asymmetric base3, 4. They are dark green and scabrous above, green-greyish and tomentose beneath3-5. This species is andromonoecious, the flowers are small, greenish, solitary or grouped in 3-5 elements, forming in the branches developed in the current year6. The fruits are drupes, ovoid or spherical, 10-12 mm in diameter, with a scant sweetish fleshy part6. The fruit colour changes from whitish to brown-reddish and then Canopy of a large plant in the botanical garden of Villa Carlotta (Como Lake, North Italy). 1, 2, 6 Map 1: Plot distribution and simplified chorology map. to blackish when the fruits ripe in late summer or autumn . (Copyright Davide Fumagalli: CC-BY) Frequency of Celtis australis occurrences within the field observations as reported by the National Forest Inventories. The chorology of the native Distribution spatial range for C. australis is derived after several sources23-27. The nettle tree is native to the Mediterranean basin and Western Asia. It occurs from Morocco and the Iberian Peninsula to Syria comprising the Mediterranean islands, up to the Black Sea and the Caucasus. It grows in lowlands and low hills from sea level to 1 200-1 300 m in Spain and Northwest Africa1-3, 6-8. In the Middle East its distribution area overlaps with the Caucasian hackberry (Celtis caucasica Willd.)3, 7, 9. They are very similar and difficult to identify; some authors consider them as subspecies10. Outside its natural range it is present as an ornamental plant in Central Europe with a northern limit set by severe winter frosts5. Outside Eurasia, this species is naturalised in Australia and in south-western United States11, 12.

Oval-lanceolate leaves with serrated margins. Habitat and Ecology (Copyright Vito Buono, www.actaplantarum.org: AP) The nettle tree grows in woods, meadows, riverbanks, cliffs, in dry and poor areas especially on rocky soils. Its strong and References 13 [1] E. Barroso, et al., Inventario Español de los [13] M. Goldstein, G. Simonetti, M. Watschinger, widely developed roots can crack rocks . It is a heliophilous Conocimientos Tradicionales relativos a Alberi d’Europa (A. Mondadori, 1995). species, preferring sunny exposures, and suffers during intense la Biodiversidad, M. Pardo de Santayana, [14] European Environment Agency, EUNIS, R. Morales, L. Aceituno, M. Molina, eds. 2 the European Nature Information System cold and late frosts . The fruits are very appetizing for birds (and (Ministerio de Agricultura, Alimentación (2015). http://eunis.eea.europa.eu. y Medio Ambiente, Madrid, 2014), pp. also for foxes, badgers and martens), which are responsible for [15] A. Bertaccini, L. Mittempergher, M. Vibio, Spherical drupe fruits in different stages of maturity. 264–269. 1 Annals of Applied Biology 128, 245 seed dissemination . It can also reproduce vegetatively by root (Copyright Vito Buono, www.actaplantarum.org: AP) [2] O. Johnson, D. More, Collins tree guide (1996). 3 (Collins, 2006). suckers . This species can be often found in thermophile mixed [16] N. Anselmi, A. Saric, G. P. Cellerino, [3] H. J. Elwes, A. Henry, The Trees of Great Informatore fitopatologico 30, 11 (1980). deciduous forests together with downy oak (Quercus pubescens), to treat liver problems (the internal part of the bark)1. The bark is Britain and Ireland Vol. 4 (Privately printed, Edinburgh, 1909). [17] L. Mittempergher, A. Sfalanga, M. Vibio, hop-hornbeam (Ostrya carpinifolia), manna ash (Fraxinus ornus), also used to make a dye, yielding a yellow pigment. The foliage A. Bertaccini, Acta Horticulturae 496, 87 [4] A. F. Mitchell, P. Dahlstrom, E. Sunesen, (1999). common hazel (Corylus avellana), and maples (Acer spp.), or in (and in some regions also the bark and thin branches) can be C. Darter, A field guide to the trees of Britain and northern Europe (Collins, [18] T. Annesi, R. Coppola, E. Motta, Forest riparian vegetation with willows (Salix spp.), poplars (Populus spp.) used as fodder for cattle1, 3, 9. 1974). Pathology 33, 405 (2003). and elms (Ulmus spp.), very rarely as the dominant species14. [5] W. J. Bean, Trees and Shrubs Hardy in the [19] T. Annesi, L. D’Amico, D. Bressanin, British Isles Volume 1: A-C (John Murray, E. Motta, G. Mazza, Phytopathologia This tree has a high growth rate and in its native range can live Threats and Diseases 1970), 8th edn. Mediterranea 49 (2011). up to 1 000 years and attain significant size2, 3. Decline of nettle tree has been registered in its Mediterranean [6] C. Navarro, S. Castroviejo, Flora Iberica: [20] A. P. Ramos, M. F. Caetano, I. Melo, Revista plantas vasculares de la Peninsula de Ciências Agrárias 31, 159 (2008). distribution area for more than fifty years, especially in towns, IbeÌrica e Islas Baleares, Volume 3: [21] L. Luongo, et al., Plant Disease 99, 155 Importance and Usage Plumbaginaceae (partim)-Capparaceae, (2015). where more than 50 % of trees were already affected by the S. Castroviejo, et al., eds. (Real Jardìn The grey-whitish wood is heavy, elastic, water resistant 1980s15, 16. Symptoms of tree weakness are evident in drought Botánico, CSIC, Madrid, 1993), pp. [22] EPPO, EPPO Bulletin 35, 456 (2005). and lasting. It has been used in the past in carriage-building, 248–250. [23] H. Meusel, E. J. Jäger, Plant Systematics years and cold winters. One of the causes seems to be the [7] H. Meusel, E. Jager, S. Rauschert, and Evolution 162, 315 (1989). in boat-building, for door or window lintels, and to make tools presence of phytoplasmas belonging to the aster yellows and E. Weinert, Vergleichende Chorologie der [24] Anthos, Information System of the plants 1, 3 Zentraleuropäischen Flora (Gustav Fischer of Spain (Real Jardìn Botánico, CSIC - and tool-handles needing good resistance . The wood was also elm yellows groups, affecting sprouting buds, fruit-set and Verlag Jena, 1978). Fundación Biodiversidad, 2015). appreciated for cabinet-making and lathe works and to produce adventitious buds15, 17. In Italy the decline of nettle tree is also [8] EPPO, EPPO Reporting Service 6 (2013). http://www.anthos.es. musical instruments (e.g. flutes, small drums) and toys for Art. 134. [25] Tela Botanica, eFlore (2015). increased by the eriophide mite Aceria bezzii, responsible for [9] P. Hanelt, ed., Mansfeld’s Encyclopedia http://www.tela-botanica.org children in the last century. Due to mechanization in agriculture the delayed sprouting of buds and loss of fruit production17. of Agricultural and Horticultural Crops [26] Sociedade Portuguesa de Botânica, Flora- and the availability of new more resistant materials, the wood (Springer, 2001). On: Flora de portugal interactiva (2014). In southern European towns the fungus Inonotus rickii was [10] C. C. Townsend, Flora of Iraq, vol 4, C. C. http://www.flora-on.pt. industry of nettle tree is in clear decline and its use is now limited discovered to contribute to the decline of the species, causing Townsend, E. Guest, eds. (Ministry of [27] J. Jalas, J. Suominen, Atlas Florae 1 Agriculture & Agrarian Reform, Baghdad, Europaeae: distribution of vascular to local handmade manufacture . This tree also produces good decay and cankers. This fungus is able to infect several ornamental 1980), pp. 65–75. plants in Europe Vol. 3 Salicaceae to 3 [11] USDA NRCS, The PLANTS database (2015). Balanophoraceae (Committee for Mapping coppice shoots when cut and yields high quality fuel wood and species making it particularly invasive and widespread in the Flora of Europe and Societas Biologica 13 National Plant Data Team, Greensboro, charcoal . Nettle tree is principally used for afforestation in urban areas18-20. The oomycete Phytophthora megasperma can USA, http://plants.usda.gov. Fennica Vanario, Helsinki, 1976). rocky and difficult terrains against erosion thanks to its frugality, [12] H. J. Hewson, Flora of Australia Volume seriously damage nettle trees, with wilting, dieback and death. 3: Hamamelidales to Casuarinales (ABRS/ for plantations in urban areas and along roads because of its The long-term survival of spores in the soil makes this threat CSIRO, Australia, 1989). pollution tolerance, and as ornamental plant for its domed crown, rather dangerous21. In its easternmost Asian Minor distribution, 13 with long arching branches . The fruits are edible and contain with a possible future extension into the Mediterranean basin This is an extended summary of the chapter. The full version of this chapter (revised and peer-reviewed) will be published online at seeds from which sweet oil can be extracted. They are also used because of the hot dry climatic conditions, nettle tree is affected https://w3id.org/mtv/FISE-Comm/v01/e0145f9. The purpose of this to produce specialist liqueurs or, in the past, to substitute sugar summary is to provide an accessible dissemination of the related by Xylotrechus namanganensis (namangan longhorn beetle or main topics. 1 during famine periods . This tree has applications for natural willow longhorn beetle). Symptoms of the presence of this pest This QR code points to the full online version, where the most medical remedies (e.g. in India and Spain) for amenorrhoea, updated content may be freely accessed. are wilting and drying leaves, holes made by larvae in the trunks, Please, cite as: diarrhoea and colic (fruits), to reduce blood pressure (leaves), as large branches and at the bases of infested trees, and beetles on Magni, D., Caudullo, G., 2016. Celtis australis in Europe: 22 distribution, habitat, usage and threats. In: San-Miguel-Ayanz, a diuretic agent or to reduce cholesterol (fruits and leaves), and the flowers and trunks . J., de Rigo, D., Caudullo, G., Houston Durrant, T., Mauri, A. (Eds.), European Atlas of Forest Tree Species. Publ. Off. EU, Luxembourg, pp. e0145f9+ 80 European Atlas of Forest Tree Species | Tree species