Acer pseudoplatanus
(sycamore)

A. pseudoplatanus is a vigorous, fast-growing tree with high light demands, and it can easily become invasive by the spread of seedlings. It is considered to be a threat to natural woodlands, particularly those on fertile soils, and in several countries is a threat to rare species assemblages or the integrity of semi-natural communities.

Broadleaved
Perennial
Seed propagated
Tree
Woody

The native distribution of A. pseudoplatanus is wide, encompassing most of central and southern Europe between 51°N and 35°N. Native range areas include Germany (Harz Mountains), Russia (Crimea and Caucasus), Spain (Pyrenees), southern and central France, the Swiss Alps, Italy, Bosnia, northern Greece and the Carpathian mountains in Poland, Slovakia and Romania. It is not native to the UK, Ireland, Belgium, Netherlands, northwest France, northern Germany and Scandinavia. All specimens of A. pseudoplatanus recorded from eastern Anatolia, Turkey have proved to be A. heldreichii subsp. trautvetteri. An incorrect record for Tanzania in a previous edition has been deleted.

Binggeli (1999) comments on the apparent disparity between the lack of published material on the invasiveness of A. pseudoplatanus outside the UK and New Zealand, and more widespread short accounts of it naturally regenerating or behaving as a weed in other countries including Russia, Germany, Denmark, Argentina and USA. It is possible that other countries have overlooked the potential invasiveness of this species and its introduction may be associated with other invasive events in the future.

A. pseudoplatanus usually forms a natural component of birch (Betula sp.) and fir (Abies sp.) forests. Binggeli (1999) compiled an extensive review of the world distribution of this species including detailed accounts of its associations within and outside its native range. In its native central European range, Binggeli (1999) reports that the distribution of A. pseudoplatanus is closely allied to that of beech (Fagus sylvatica) and that it occurs as minor component of mature beech, fir and spruce (Picea abies) forests. It is also found in wet lowland and riparian communities in association with alder (Alnus), ash (Fraxinus) and elm (Ulmus) (Binggeli, 1999). Binggeli reports that it has a low competitive ability in comparison with beech but is able to become a dominant species on unstable strata such as scree slopes.

Cronk and Fuller (1995) report that this species invades semi-natural woodlands and nutrient-rich wasteland. Where the species occurs outside its native range and has naturalized or become invasive, namely in the UK, Ireland, Chile and New Zealand, habitats include river corridors, planted forest, roadsides, abandoned farmland, urban wasteland, railway lines, gardens, hedgerows, native and semi-natural woodland, high country tussock grassland especially in New Zealand, also laurel forest in Madeira, Portugal (Binggeli, 1999).

Studies cited by Binggeli (1999) describe this species as a weed in Christmas tree (Picea abies) plantations in Denmark and commercial beech (Fagus sylvatica) plantations in Sweden.

Genetics

A. pseudoplatanus ecotypes have been identified which follow an altitudinal range (Mayer, 1977). Results of the comparison between six UK and four other European provenances in height and root-collar diameter show that of the four continental European provenances, two from Denmark and Germany performed better than the UK provenances (Cundall et al., 1998). Variability of progeny characteristics has been studied by Bojovic (1991) and Weiser (1996). In vitro growth of A. pseudoplatanus callus on metal-enriched media has allowed the identification of some lines particularly adapted to metal stress (Watmough and Dickinson, 1995). Isoenzyme analysis of A. pseudoplatanus has been used for clonal identification (Konnert, 1992). Most of the subspecies and varieties described in the literature should be treated as forms, but many of them may only deserve cultivar status (van-Gelderen et al., 1994). Several nurseries and research stations have selected or developed cultivars for landscaping. In cultivation, hybrids between A. heldreichii subsp. tautvetteri and A. pseudoplatanus frequently occur (van-Gelderen et al., 1994). A number of hybrid trees can be found in various arboreta, sometimes labelled correctly as A. x pseudo-heldreichii Fukarek & Celjo.

Physiology and Phenology

A. pseudoplatanus is a shade tolerant species that can live for up to 500 years (Binggeli, 1999). It is able to produce seed within the first few years of growth and although seedling production is prolific there is high mortality of self-sown plants within the first year and thus in describing the spread of this species it is important to distinguish between seedlings and saplings older than one year (Binggeli, 1999).

Reproductive Biology

Each flower is monoecious. A. pseudoplatanus is generally outbreeding and can produce in the order of 10,000 wind-dispersed seeds each year (Cronk and Fuller, 1995).

Environmental Requirements

A. pseudoplatanus is found over a wide range of latitudes, from the Peloritani Mountains in Sicily to the Carpathian Mountains in Poland. Best growth occurs where mean annual rainfall exceeds 1200 mm and mean annual temperature is about 12-13°C. However, it is very resistant to cold, tolarating absolute minima of -30°C, probably due to the late flushing which protects it from early and late frosts. Both winter and bimodal rainfall regimes are tolerated, with preferred mean annual rainfall in the range 600-1600 mm, but only short dry seasons of less that 3 months are tolerated.

A. pseudoplatanus can grow on a wide variety of soils, but best growth is found on moist fertile soils over limestone or chalk. The only soil it will not tolerate is pure clay. The pH level of the soil ranges from 5 to 8. More often found in places rich in available nitrogen, though it can survive infertile and saline soils and on sites contaminated with heavy metals. The altitudinal range is generally between 500 and 1900 m.

Associations

Binggeli (1999) reports that the distribution of A. pseudoplatanus is closely allied to that of Fagus sylvatica, and that it occurs as minor component of mature Fagus, Abies and Picea forests. It is also found in wet lowland and riparian communities in association with Alnus, Fraxinus and Ulmus (Binggeli, 1999).

Although A. pseudoplatanus is exposed to a number of fungal attacks, few are serious. One serious pathogen is Verticillium sp. which can cause both chronic and acute wilting of the foliage and crown, and Cristulariella depraedans causes spotting and withering of the leaves (Moore, 1959). By far the commonest cause of tar spot of A. pseudoplatanus is Rhytisma acerinum, and in Europe it is common wherever A. pseudoplatanus is grown, except in the polluted atmosphere of large industrial towns (Jones, 1944) and in very upland or montane areas (Maxwell, 1933). Though in severe attacks, R. acerinum causes some premature defoliation, and some may regard its black stromata as unsightly on trees grown for ornament, its effects are rarely serious. The imperfect fungus Cryptostroma corticale has been found in the USA and in the UK, France and Germany (Plate and Schneider, 1965). It causes wilting and dieback of affected branches, and infected trees usually die within a few years. Virus-like symptoms (leaf deformation and mottling) related to the tobamovirus group have been detected on A. pseudoplatanus in western Germany (Fuhrling and Buttner, 1998). A. pseudoplatanus can harbour root galls (van-Gelderen et al., 1994). A. pseudoplatanus is not particularly subject to serious insect infestations (Johnson and Lyon, 1988). However, Gilman and Watson (1993) note that in the USA it is susceptible to several pests and diseases which have a negative impact on tree health or appearance.

Animal feed, fodder, forage

• Fodder/animal feed

Environmental

• Agroforestry
• Shade and shelter
• Windbreak

General

• Ornamental

Genetic importance

• Gene source

Materials

• Carved material
• Miscellaneous materials
• Wood/timber

Containers

• Boxes

Furniture

Sawn or hewn building timbers

• Carpentry/joinery (exterior/interior)
• Flooring
• For light construction

Veneers

Woodware

• Brushes
• Industrial and domestic woodware
• Musical instruments
• Tool handles
• Toys

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Manual removal of seedlings and saplings is possible, i.e. hand pulling and digging up, but the roots must be completely removed, or cut stumps must be treated with a herbicide in order to prevent regeneration (Weber, 2003).