Cultivated plants in Northern Ireland

This website gives an insight into the huge diversity of plants cultivated within Northern Ireland which come from all the corners of the globe, with the emphasis on trees and shrubs rather than herbaceous plants. The trees include those planted in gardens or parks or as wayside amenity plantings, shelter belts etc.

Please note it is currently under development and further species and information will be added from time to time.

How many species?

The total number of species of ferns and seed plants (collectively called the 'vascular plants') living on earth today is estimated at about 250,000. The total number of wild vascular plant species living in Northern Ireland is probably around 1500 at most. Of these about 900 or so are natives and the remainder are introductions (aliens) brought in by man.

However, the total number of species (mostly foreign) cultivated in Northern Ireland is vastly in excess of this number, perhaps as many as 30,000. The total for the entire British Isles is probably about 55,000 - about a quarter or so of the entire world vascular plant flora!

Why so many foreign species? - the climatic factor

A combination of climatic/geographical factors has produced one of the most equable climates in the British Isles, which can therefore support an exceptionally wide range of plants; this encompasses tender species from Chile, Tasmania and New Zealand in the southern hemisphere. One other result has been the encouragement of the growth of many 'champion' trees in Northern Ireland.

  • The 'Continental' effect, of very cold winters with lots of frost, and hot, dry summers, is at a minimum, as Northern Ireland is at the extreme western edge of Europe; it therefore benefits greatly from the ameliorating effects of the Atlantic Ocean, and in particular from the North Atlantic Drift, the great current which brings warm water from the West Indies to Europe. This contributes to ..........
  • Usually very mild winters, giving greatly extended growing seasons - spring starts earlier and winter arrives later, and is shorter than in many other areas of the British Isles, which also contributes to ..........
  • Quite high humidity, which is also relatively constant ie with little variation, and few droughts - therefore many more temperamental/delicate plants requiring constant humidity can survive, which would not last in eastern regions of the British Isles, where there are both greater variation and greater extremes.
  • The east coast of Northern Ireland is particularly favoured, with more hours of sunshine, giving averagely higher summer temperatures, which, allied with long day length in the summer, produce ideal growing conditions in peak growing months.

Severe weather

The impoverishment, both catastrophic and gradual, of important collections in the south and east of the British Isles, means that those in the west and north have become relatively more and more valuable, as they have not suffered to the same extent.

  • Northern Ireland did not experience the two 'great' gales of 1987 and 1990, when catastrophic damage was done to the south of England, with the loss of many mature trees.
  • Because of the windier climate in the north and west, trees here have become accustomed to the stresses of gales.
  • The south and east of Great Britain is gradually getting drier (spreading at a suggested rate of 10km per year), with the summer climate more like that of the Mediterranean; many gardens, therefore, have suffered from drought, and lost important species, some of which now are only represented in the British Isles in Northern Ireland.

Notable features

  • Northern Ireland's climate is excellent for the growing of trees from North America, New Zealand and many other countries. Some of our most familiar semi-wild shrubs and trees, like the fuchsia from Chile, the sycamore from Europe or the snowberry from North America, are fairly recent introductions from abroad. Unfortunately some of these species have become pests and nuisances, like Japanese knotweed and Rhododendron ponticum.
  • The great plant collections of Northern Ireland estates and gardens contain many rare plants collected from all over the world, some of which may now be extinct in the wild, meaning that the genetic diversity represented in these collections is particularly valuable on a world scale. Great plant collectors are well represented in these gardens as well.
  • The degree to which gardens here have successfully tried and adopted exotics is highlighted by the escape and naturalisation of many garden species, some of which in other regions of the British Isles are regarded as tender - ranging from flowering currant, New Zealand privet and hebe to fuchsia, New Zealand flax and daisy bushes. Some species, such as Olearia paniculata, grow much larger than they do in their native habitats.
  • The presence of so many exotics means that gardens in Northern Ireland, with their great ranges of rhododendrons, bamboos, tree ferns and many other species, present a noticeably different appearance - the colour palette alone has acquired brilliant azaleas and rhododendrons and the grey-greens of the New Zealand flora.


This huge collection of introduced flora, which is distributed through large gardens, demesnes, parks, ordinary suburban gardens and wayside plantings, is a significant reservoir of plant biodiversity. Some species are commoner in cultivation than they are in their wild homes and may one day provide a source for re-introduction into the wild. Unfortunately, the genetic diversity of many cultivated plants is much smaller than that of the wild populations and some species are only known in cultivation as a single clone or genotype (such as Japanese knotweed).

Economically Important Plants

As well as the plants grown for ornament ('garden plants') the introduced flora also includes all the economically important crop plants and timber-producing trees. Virtually none of the species of crop plants, whether of cereals, fruit, other food plants, oil-producing plants or fibre-producing plants, is indigenous to Northern Ireland.

The only exceptions are the forage plants such as the grasses and clovers which are sown in artificial leys, and even in these cases many of the commercial varieties of these species are derived from sources outside Ireland and are consequently genetically distinct from our wild populations.

The Wild Plants of Northern Ireland

If you want to know more about the wild flora of Northern Ireland go to our Flora of Northern Ireland web site.

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