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In Ireland, like in Britain, sycamore pollen has not been recorded in any pre-17th century pollen diagrams (e.g. Hirons & Edwards 1986, Mitchell 1988, Hall 1990) and this indicates that the species is not native. This is further supported by the fact that no place name derived from sycamore exists in Ireland (McCracken 1971), whereas many originated from other tree species like oak. Sycamore (Crann bán in Irish, Webb 1977) was first recorded in Ireland in 1632 (Fitzpatrick 1933). Plantings of sycamore made prior to 17th century were in shelter belts, orchards and avenues on estates around Dublin and Cork and planting blocks began around 1700 (McCracken 1971). By 1756 in Co. Kerry Dr Smith was urging his readers living near the sea to plant this tree: "of all timber trees none thrive so well near the turbulent element as the sycamore, which will flourish where scarce any other tree will grow. It bears the spray of the sea very well itself, and by its breadth of leaf excellently defends any other tree from it in the summer, and is of so quick a growth that its body and arms soon become qualified to do the same in winter" (Scully 1916). By the 18th century enough sycamore had been grown to be felled and sold; McCracken (1971) reports that out of about 200 advertisements for sale of timber which appeared in Faulkner's Dublin Journal between 1731 and 1763 five list sycamore. The fact that sycamore was added to the list of woods allowed in the making of barrels used in the export of meat, butter, tallow and fish in 1732 underlines its availability and economic importance. The report that "The grand sycamore at the gate of Castlecosby, Co. Cavan] was uprooted, and thrown into the stable yard, carrying the gate and piers..." (Carr 1991, p 77) during the great wind of 1839 indicate that some very large trees existed at that time. The 19th century saw the rise of sycamore and other exotics (McCracken 1971). In more recent times sycamore timber has been of high value for turnery, furniture and flooring. It wears slowly and smoothly and has been sought after for the floors of dance halls (Fitzpatrick 1966). 

Sycamore's altitudinal distribution ranges from sea level up to 280m in Kerry (Scully 1916). There is a large variation in habitat types described as being occupied by sycamore in Ireland, and it is not clear whether this reflects a county to county variation or the observer's perception. In Cos Antrim and Derry, Stewart & Corry (1888) recorded sycamore along several rivers and found it common in plantations and by roadsides. In Co. Kerry sycamore was rather common in hedges, wood, plantations and about houses according to Scully (1916). This century, other authors (e.g. Webb 1977) describe sycamore as being commonly planted and as occurring mainly in hedges, woods and plantations. Brunker (1950) gives thicket as another habitat. 

Perring & Walters' (1962) sycamore distribution map show that it now occurs in most 10km squares, except in Connemara, Mayo and some parts of Central Ireland. In Dublin, sycamore is probably the commonest tree in the inner city (Wyse Jackson & Sheehy Skeffington 1984).

Personal observations indicate that sycamore is very common along the west coast mainly around farmsteads, woods of large estates and along river banks. In many exposed areas ash is the only other tree which may also be common. In the centre of Ireland sycamore has been less commonly planted. For instance, in Co. Kilkenny, horse-chestnut appears to have been favoured instead of sycamore. To the west of the Antrim hills beech is much more frequent. 

Recent surveys of sycamore distribution

Near Knock (Co. Mayo), sycamore occurred in 9.7% of the hedges (6.3% of pre-1837 and 13.3% of post 1837 hedges) and was the eighth most common woody species out of a total of ten species (Condon & Jarvis 1989). In Co. Meath it was the fourth commonest species representing 8% of the total number of trees, but few individuals were represented in the sapling class (Webb 1985). In Northern Ireland, Graham (1980) found that sycamore constituted only 1% or so of the shrub layer composition of hedges in Cos Derry and Antrim. On the other hand sycamores in hedgerows and parklands were common (about 20% composition by volume) and was in all six counties the second or third commonest species. Within all counties of Northern Ireland there is wide variation in occurrence. For example, in Co. Fermanagh, Murray et al. (1991) found that 6% of all field boundaries contained sycamore, but it was more common in hedges and at intermediate altitude and absent in the mountains (Table 3).

Table 3. Percentage of various field boundaries in different landscape units in Fermanagh with sycamore. Landscape units are: A. Lakeland environment, B Small drumlin, C. Larger drumlin, D. Intermediate elevational slopes (100-110m), E. Upland 100-300m, F. Mountain, >300m (data reworked from Murray et al. 1991)

An extensive literature exists on the distribution of sycamore in Northern Ireland, particularly in Areas of Outstanding Natural Beauty (AONBs), following the landscape studies of Cooper and co-workers (e.g. Cooper & Murray 1987, Murray et al. 1991) and Tomlinson et al. (1987). The study of the Mourne AONB (Cooper & Murray 1987) illustrates the importance of sycamore in the Irish landscape. It is the commonest tree around farmsteads and as lines or groups of scattered trees and its importance diminishes in fields and semi-natural woodlands (Table 4).

Table 4. Percentage frequency and rank of sycamore in different habitat types of the Mourne AONB (data reworked from Cooper & Murray 1987).

A survey of Northern Irish private woodlands by Graham (1981) showed that sycamore occupied 6% of the total area of woodland greater than 0.5ha and that most were planted before 1929, and some between 1929 and 1954, but none since. By volume sycamore was the fifth commonest species and represented 12% of the total. Within Northern Ireland large variations were observed. It is the second most important species (20%) in Co. Derry, was common in Tyrone, Antrim, Down and Armagh with about 10% but was absent from Fermanagh. Sycamore occurred mostly on leached soils and sometimes on gleyed soils and was the second most productive broadleaf after beech. In Co. Antrim, Tomlinson et al. (1987) found that ash and sycamore were the commonest tree species and most submature woodland trees belonged to these two species, and they forecast a large change in species composition in future decades.

Sycamore stands in State and private broadleaved woodland of the Republic of Ireland represent about 7% of the total or 3400 ha, but pure sycamore woodlands only account for 69ha (55 stands), the rest consisting of mixtures. Sycamore is the fourth commonest tree species (Fitzsimons 1987, Keogh 1987) in Ireland.

In a recent survey of 200 forest plantations in the whole of Ireland Blackstock (unpublished data) found that the probability of occurrence of sycamore in a plantation increased from 8% in the south-east of the island to 39% in the north-east. The probability of occurrence also decreased with altitude, though at any given altitude the probability was higher at a northern than at a southern location. Blackstock (pers. comm.) suggests that this pattern is typical of a climatically controlled distribution. However, it is difficult to suggest a climatic variable which would produce such a pattern. The 762mm annual average rainfall threshold suggested as a minimum for the spread of sycamore in woods of Great Britain (Pigott 1984) does not appear to apply to sycamore regeneration in Irish plantations. It is possible that the observed pattern reflects the distribution (seed source) of sycamore in Ireland, but no data are available.

In a survey of 26, probably planted, deciduous woodlands in north-east Co. Down, Cooper (1986) found that sycamore was present and often dominant in all base-rich woods and occurred in half of the acidic woods. In both woodland types sycamore and beech were the commonest trees. Sycamore was regenerating in the base-rich woods but was poorer in the acidic woods. He concluded that sycamore's poor regeneration on acid sites is due in part to grazing, but at higher elevations, on more acidic soils, sycamore is likely to be much more common as canopy dominants than it is at present because of regeneration failure of other species.

Semi-natural woodlands and nature reserves

According to the Countryside and Wildlife Branch Warden's Annual Reports for 1987-1988 (Anon 1988a) sycamore was controlled in four out of the 17 reported reserves. Reas Wood, Co. Antrim was not included, though it contains a large population of sycamore and thus the number of reserves containing sycamore is probably much higher. Sycamore is the commonest species on Murlough sand dunes (Co. Down), a National Trust Nature Reserve and has increased by about 200% between 1968 and 1978 (Whatmough 1978).

In an ecological survey of 22 hazel woodlands of North Down and South Antrim, Cooper (1984a) found that four sites contained sycamore or beech as canopy dominants. In woodlands not dominated by exotics, three main groups of vegetation quadrats were identified and sycamore occurred in well drained nutrient-rich samples and acidic samples (30 and 20 stems respectively per ha, stem >5cm DBH), but not in poorly drained nutrient rich samples. One of the sites, Knockagh (Greenisland, Co. Antrim), was investigated in more detail (Cooper 1984b) but sycamore occurred in very few numbers in sample quadrats. However, Cooper (1984b) considered that potential canopy closure by sycamore was a threat to the hazel type of communities and that its prevention should be considered as a priority in any management programme.

A survey of the status of sycamore in woodlands of the north of Ireland carried out by Freeman (1992) reveals that sycamore is present in 76% of the 50 randomly located woodlands but no geographical variation was observable. Sycamore free sites were all classified as semi-natural woodlands dominated by hazel. However it is not clear from the study whether sycamore has invaded woodlands in which it is present or whether it was planted. The assessment of sycamore regeneration does not differentiate between seedlings (<1yr old) and saplings (>1yr old) an important distinction as naturally regenerated sycamores do not usually survive the seedling stage and is therefore not conclusive (see 'Which stage in the sycamore life cycle limits its spread?').

In ash dominated woodlands of Western Ireland, on free-draining soils over limestone, sycamore was recorded at only one site by Kelly & Kirby (1982). In that wood sycamores >20cm DBH had a mean density of 1.7 trees per ha while that of saplings was 20.7 stems per ha. Sycamore was not recorded in hazel scrub in the Burren.

Although the Killarney oak forests are extensively invaded by Rhododendron ponticum (Cross 1982), sycamore is widespread in the Carboniferous area, though regeneration is very local (Kelly 1981). 

Other studies show that sycamore has not invaded some types of semi-natural woodlands. Examples include Gearagh wood (Co. Cork), a floristically rich (38 woody species) alluvial forest, dominated by Alnus glutinosa (White (1985) and three Co. Cork woods investigated by Iremonger (1990).

Evidence of its invasive abilities

The existence of natural regeneration in sycamore was first documented by Dr. Smith in Co. Kerry in 1756, where it was described as sowing itself not infrequently (Scully 1916). During the 19th century conflicting reports appeared. On the one hand J. Templeton (Praeger et al. 1938) wrote "Not yet perfectly naturalized as I have found it nowhere in an uncultivated state except a single tree among the natural wood along the margin of Lough Neagh, February 1796." He added: "Observed several trees about 1 foot [30cm] diameter among oaks and other natural wood on the shore of Lough Neagh in Shane's Castle Park, Sept. 25, 1804" and Stewart & Corry (1888) wrote that sycamore was never really wild. On the other hand, Colgan & Scully (1898) state that sycamore freely reproduces itself from seed in many places, occasionally spreading to peat bogs in the neighbourhood of plantations.

This century, all authors describe sycamore as self-sown (e.g. Praeger et al. 1938, Webb 1977). Praeger (1950) depicts it as windsown in rough glens, on cliffs, and islets in lakes and among native vegetation. Fitzpatrick (1933) describes sycamore as a common tree which "grows freely in the most exposed places, producing an abundance of seed from which self-sown seedlings spring up in great numbers." In the centre of Dublin sycamore seeds itself freely in many habitats and Wyse Jackson & Sheehy Skeffington (1984) believe it is planted much less frequently than it is self-sown. Brunker (1950) writes that sycamore's "windborne seeds are widely scattered, and strike so freely as to become, at times, a nuisance. No doubt a large number of trees, particularly in hedgerows, are due to natural distribution; and it may sometimes be found in wild ground a long way from any possible source of the seed." McEvoy (1944) remarked that sycamore regenerates freely particularly on disturbed ground (e.g. gardens and cut-over woods), but its ability to invade most woodland unaided, is inferior to beech. He adds that regeneration under deep shade suffers severely from tar-spot fungus Rhytisma acerinum and its height growth is less than that of native competitors. Fitzpatrick (1966) has a slightly different opinion: "Fertile limy soils suit it best and, given suitable soil, it is quick to colonise open spaces in woods of other species; it is difficult, however, to establish on new ground."

Praeger et al. (1938), well aware of the self-sowing ability of sycamore, suspected that the capacity was only recently achieved in light of Templeton's evidence. The above review suggests that in some instances this is possible, but it is more likely that the speed of the invasion is slow. 

Mitchell (1976, 1986) has briefly discussed the reason for the spread of sycamore. He suggests that because it buds earlier than natives such as oak and ash (opposite of the New Zealand situation, see Status in New Zealand), sycamore is "taking an advantage of the sunshine", while late budding in natives is an ancestral condition to escape late killing frosts when the climate was less oceanic than today. He implies that sycamore is less frost tolerant than oak and ash. When the ranges of ash and sycamore are compared, ash occurs at higher latitudes whereas sycamore occurs at higher altitudes in the Alps, clearly indicating that factors other than frost are involved in determining their respective distributions. Furthermore, Acer platanoides, a frost tolerant species reaching similar latitudes as ash, also failed to reach the British Isles.