The 25th July 2021 marks 400 years of botanical research and teaching by the University of Oxford.

As a celebration and count-down to this anniversary, the University of Oxford Botanic Garden and Harcourt Arboretum, together with the Oxford University Herbaria and the Department of Plant Sciences, will highlight 400 plants of scientific and cultural significance. One plant will be profiled weekly, and illustrated with images from Oxford University's living and preserved collections.

  • Plant 48: Rosmarinus officinalis
  • Plant 47: Ptelea trifoliata
  • Plant 46: Acer saccharum
  • Plant 45: Brassica oleracea
  • Plant 44: Helianthus annuus
  • Plant 43: Ricinus communis
  • Plant 42: Simmondsia chinensis
  • Plant 41: Chara sp.
  • Plant 40: Zingiber officinale
  • Plant 39: Aristolochia clematitis
  • Plant 38: Allium cepa
  • Plant 37: Galium tricornutum
  • Plant 36: Artemisia annua
  • Plant 35: Rosa canina
  • Plant 34: Nepenthes rajah
  • Plant 33: Dianthus caryophyllus x Dianthus barbatus
  • Plant 32: Taraxacum sp.
  • Plant 31: Victoria cruziana
  • Plant 30: Lathyrus odoratus
  • Plant 29: Heliconia rostrata
  • Plant 28: Senecio squalidus
  • Plant 27: Paulownia tomentosa
  • Plant 26: Urtica dioica
  • Plant 25: Euphorbia characias
  • Plant 24: Heliamphora nutans
  • Plant 23: Laurus nobilis
  • Plant 22: Tulipa sylvestris
  • Plant 21: Pleurococcus sp.
  • Plant 20: Gleditsia triacanthos
  • Plant 19: Tillandsia usneoides
  • Plant 18: Marchantia polymorpha
  • Plant 17: Daphne mezereum
  • Plant 16: Citrus medica
  • Plant 15: Coffea arabica
  • Plant 14: Gossypium species
  • Plant 13: Stachyurus praecox
  • Plant 12: Encephalartos ferox
  • Plant 11: Aloe vera
  • Plant 10: Araucaria angustifolia
  • Plant 9: Isoetes echinospora
  • Plant 8: Hamamelis virginiana
  • Plant 7: Lithops species
  • Plant 6: Sequoiadendron giganteum
  • Plant 5: Commiphora saxicola
  • Plant 4: Buxus sempervirens
  • Plant 3: Picea abies
  • Plant 2: Cinnamomum verum
  • Plant 1: Taxus baccata

  • Follow us on Twitter @Plants400

    The data and images available on this site may only be used for scientific purposes. They may not be sold or used for commercial purposes. All images are copyright of the University of Oxford, unless otherwise indicated.

    The specimens at the Oxford herbaria and the living collections of the Oxford Botanic Garden and Oxford University Herbaria are being digitized using BRAHMS.


    Dr Alison Foster (

    Dr Stephen Harris (

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    Plant 49

    Fraxinus excelsior L. (Oleaceae)


    Common ash


    Common ash, also known as European ash, is one of more than 45 species in the genus, with the greatest diversity in North America and Asia. It is a deciduous broadleaved tree with a widespread natural distribution from Ireland, in the west, to continental Russia (almost to the River Volga), in the east. It reaches to 64° N in Norway and to the northern parts of Italy, Spain and Greece in the Mediterranean, and as far south as 37° N in Iran. It will survive on a wide variety of soil types, but good growth is generally limited to fertile, alkaline, soils.

    Ash features in a range of ways in European culture: the rhyme, Oak before Ash, in for a splash, ash before Oak, in for a soak, which notes the pattern of spring leaf flushing is also found in German and Norwegian. In Norse mythology, Yggdrasil was the hollow ash tree from which the first man, Ask ('Ash') emerged. Throughout its distribution its wood is widely used, its flexibility giving it particular value in tool handles and sports equipment. In Ireland there is high demand for ash trees to make 'hurleys' used in the Gaelic sport of hurling. Ash leaves have been used as fodder and the unripe ash keys (fruit) in cooking as alternatives to capers.

    Ash is wind pollinated with the flowers opening before leaf flush in spring. With a range of flower types: male, female and hermaphrodite, some trees are entirely male, others female and others hermaphrodite, with mixtures of male and hermaphrodite or female and hermaphrodite flowers on the same tree. Some trees will even change sex from one year to the next, with hermaphrodite trees becoming more female or male.

    Common ash has proven particularly susceptible to dieback caused by the fungus Hymenoscyphus fraxineus, with more than 60% of trees dying in parts of Europe, since its spread west from first observation in Poland in 1992. Its detection in Britain in 2012 resulted in a media frenzy and the start of intensive projects to sequence the ash genome and to find trees with resistance or low susceptibility to the fungus. On the horizon is another threat, the emerald ash borer which has been observed close to Moscow and already caused large scale damage to Fraxinus species in the USA. Key to the future of Fraxinus excelsior will be its high levels of genetic diversity.

    The British Ash Tree Genome Project 2014.

    Fraxigen 2005. Ash species in Europe: biological characteristics and practical guidelines for sustainable use. University of Oxford.

    Nornex 2014.

    David Boshier