It is useful to distinguish native trees (which arrived in Ireland naturally) from introduced, or alien, trees which have been brought in by man for ornament, timber or other uses.
Note that many now familiar trees of the modern Irish landscape, such as beech (Fagus sylvatica), poplars (Populus x canadensis etc), horse-chestnut (Aesculus hippocastanum), sweet chestnut (Castanea sativa), sycamore (Acer pseudoplatanus), Norway maple (Acer platanoides), lime (Tilia spp.) and all coniferous trees except yew (Taxus baccata) and juniper (Juniperus communis) have been deliberately introduced to Ireland.
The trees which are native to Northern Ireland are:
| Elm | Ulmus glabra |
| Oak | Quercus petraea and Q. robur |
| Hazel | Corylus avellana |
| Birch | Betula pubescens and B. pendula |
| Ash | Fraxinus excelsior |
| Yew | Taxus baccata |
| Alder | Alnus glutinosa |
| Aspen | Populus tremula |
| Rowan and whitebeams | Sorbus spp. |
| Holly | Ilex aquifolium |
| Elder | Sambucus nigra |
| Cherry | Prunus avium |
| Bird-cherry | Prunus padus |
| Blackthorn | Prunus spinosa |
| Hawthorn | Crataegus monogyna |
| Purging buckthorn | Rhamnus catharticus |
| Alder buckthorn | Frangula alnus |
| Spindle | Euonymus europaeus |
| Crab | Malus sylvestris |
Scots pine (Pinus sylvestris) became extinct before 1700, but was re-introduced from Scotland and other parts of northern Europe.
| © National Museums and Galleries of Northern Ireland and Environment and Heritage Service, 2000-2004 |