Acer negundo (box elder)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Plant Type
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Hosts/Species Affected
- Biology and Ecology
- Latitude/Altitude Ranges
- Air Temperature
- Soil Tolerances
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Pathway Vectors
- Plant Trade
- Impact Summary
- Environmental Impact
- Impact: Biodiversity
- Social Impact
- Risk and Impact Factors
- Uses List
- Wood Products
- Similarities to Other Species/Conditions
- Prevention and Control
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Acer negundo L.
Preferred Common Name
- box elder
Other Scientific Names
- Negundo aceroides Moench
- Negundo negundo (L.) Karsten
- Rulac fraxinifolia Adanson
- Rulac negundo (L.) Hitchc.
International Common Names
- English: ashleaf maple; ash-leaved maple
- Spanish: arce; fresno de Guajuco
- French: erable a feuilles de frene
Local Common Names
- Canada: aulne-buis; box-elder maple; érable; érable à feuilles composées; érable à feuilles de frêne; érable à Giguère; érable à Giguère pubescent; érable argilière; érable du Manitoba; érable négundo; inland box-elder; inland Manitoba maple; plaine à giguère
- Germany: Eschen- Ahorn; Eschenahorn
- Iran: afraie-zinati
- Italy: acero a foglie di frassino; acero americano
- Netherlands: vederesdoorn
- Poland: klon jesionolistny
- Sweden: ask lönn
- USA: inland boxelder; Manitoba maple; western boxelder
- ACRNE (Acer negundo)
Summary of InvasivenessTop of page
A. negundo is a small and variable tree of little economic value native to much of North America. It has been widely planted mainly for amenity purposes in non-native parts of North America, Europe and Asia where it is now regenerating freely and spreading, invading riparian zones and urban areas. In the temperate parts of the southern hemisphere the spread of A. negundo is more limited. Although this pioneer species is invasive throughout much of its introduced range, actual impacts are not great. This species has no important negative impacts on human activities. In natural habitats the species becomes an important component of the vegetation in riparian systems and increases siltation.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Spermatophyta
- Subphylum: Angiospermae
- Class: Dicotyledonae
- Order: Sapindales
- Family: Aceraceae
- Genus: Acer
- Species: Acer negundo
Notes on Taxonomy and NomenclatureTop of page
Although A. negundo is now firmly part of the genus Acer, until relatively recently its taxonomic status has often been debated (de Jong, 1976). The differences, and its reproductive biology (e.g. dioecy) in particular, exhibited by A. negundo when compared to other species of the genus lead some taxonomists to ascribe the species to a separate genus negundo. A number of varieties has been described in its native range in North America (Rosario, 1988). These are: var. negundo L., var. interior (Britt.) Sarg., var. violaceum (Kirchn.) Jaeg., var. texanum Pax., var. californicum Sarg. and var. arizonicum Sarg. These varieties are differentiated on the basis of morphological characteristics, mainly pubescence or colour of the branches and/or samaras, and sometimes leaf shape (Anon., 1963; Rosario, 1988). Being an important ornamental tree, many cultivars exist but the variegated forms are the most commonly planted (Gelderen et al., 1994).
DescriptionTop of page
A. negundo is an often multi-stemmed tree reaching a height of no more than 20 m and a stem diameter of up to 1 m (Rosario, 1988). In more open vegetation the canopy usually exhibits a broad and open crown and may even become shrubby, whereas in the face of competition in a forest stand the trunk tends to be single-stemmed and straighter. Shoots are green and turn violet in the second year. The bark is grey-brown becoming dark grey and is shallowly cracked. Buds are opposite, small, 2-5 mm, two-scaled and silky white. The leaves are 15-35 cm long, pinnate with 3-5 (or 7) leaflets and light green but paler below. The leaflets are lobed and serrated. Leaflet shape is variable, for instance in var. interior the first pair of leaflets is 3-lobed. Male flowers are born in corymbs with pendent stamens whilst female flowers are in small pendent racemes. Both types of flowers are small and pale yellowish-green in colour. There is much variation in the morphology of pistillate flowers with the presence of stamens on a proportion of the flowers (Hall, 1951). The fruit consists of two fused winged samaras to 4 cm long, diverging at an angle of less than 60 degrees. The samaras separate when shed and contain a single wrinkled seed.
Plant TypeTop of page Perennial
DistributionTop of page
The natural distribution of A. negundo ranges from southern Canada to the mountains of Mexico and as far as Guatemala, is absent from western North America but occurs along the Atlantic coast. The various recognized varieties appear to represent fairly distinct geographic races but these often intergrade (Rosario, 1988). The range of the species has greatly expanded in North America through planting and subsequent natural regeneration and is spreading in the western USA. In Canada, although only native to the southern tip of Ontario, A. negundo is now naturalized in western provinces from Ontario to Nova Scotia (Anon., 1963). The species is widespread in urban areas throughout much of Europe following centuries of horticultural and landscape planting. It is probably more widespread in other temperate regions of the world but is absent from the tropics.
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Planted||Reference||Notes|
|China||Present||Introduced||Planted||Cao et al., 1992|
|-New Brunswick||Present||Introduced||Invasive||Planted||Rosario, 1988|
|-Prince Edward Island||Present||Introduced||Invasive||Planted||Rosario, 1988|
|-Yukon Territory||Present||Introduced||Bennett et al., 2010|
|-New Hampshire||Present||Native||Natural||Rosario, 1988|
|-New Jersey||Present||Native||Natural||Rosario, 1988|
|-New Mexico||Present||Native||Natural||Rosario, 1988|
|-New York||Present||Native||Natural||Rosario, 1988|
|-North Carolina||Present||Native||Natural||Rosario, 1988|
|-North Dakota||Present||Native||Natural||Rosario, 1988|
|-South Carolina||Present||Native||Natural||Rosario, 1988|
|-South Dakota||Present||Native||Natural||Rosario, 1988|
|-West Virginia||Present||Native||Natural||Rosario, 1988|
Central America and Caribbean
|Argentina||Restricted distribution||Introduced||Planted||Simberloff et al., 2002|
|Austria||Restricted distribution||Introduced||Invasive||Planted||Drescher and Magnes, 2002|
|Bulgaria||Present||Introduced||Planted||Tutin et al., 1968|
|Czech Republic||Restricted distribution||Introduced||1835||Invasive||Pysek et al., 2002; Pysek and Prach, 2003|
|Germany||Restricted distribution||Introduced||1736||Invasive||Sachse, 1991; Kowarik, 1992|
|Hungary||Restricted distribution||Introduced||Invasive||Planted||Török et al., 2003|
|Poland||Restricted distribution||Introduced||1800||Invasive||Zajac et al., 1998; Medrzycki and Pabjanek, 2001|
|-Central Russia||Restricted distribution||Introduced||Planted||Adamowski, 1991|
|-Northern Russia||Restricted distribution||Introduced||Planted||Adamowski, 1991|
|-Russian Far East||Restricted distribution||Introduced||Planted||Adamowski, 1991|
|-Southern Russia||Restricted distribution||Introduced||Planted||Adamowski, 1991|
|-Western Siberia||Restricted distribution||Introduced||before 1940||Invasive||Planted||Adamowski, 1991|
|Slovakia||Present||Introduced||1699||Tutin et al., 1968; Lohmeyer and Sukopp, 1992|
|Spain||Present||Introduced||Planted||Tutin et al., 1968|
|Sweden||Restricted distribution||Introduced||Invasive||Planted||Stöcklin et al., 2003|
|Switzerland||Present||Introduced||Planted||Tutin et al., 1968|
|UK||Restricted distribution||Introduced||1688||Not invasive||Planted||Clement and Foster, 1994|
|Ukraine||Restricted distribution||Introduced||Invasive||Planted||Mosyakin and Yavorska, 2002|
|-New South Wales||Restricted distribution||Introduced||Invasive||Planted||Howell and Benson, 2000|
|-Queensland||Present||Introduced||Planted||Groves and Hosking, 1997|
|-Victoria||Present||Introduced||Invasive||Planted||Groves and Hosking, 1997|
|New Zealand||Present||Introduced||Invasive||Planted||Webb et al., 1988|
History of Introduction and SpreadTop of page
A. negundo was introduced to the UK in 1688. It was then planted throughout much of Europe but the history of introduction and spread through the continent is fragmentary. It was reported as spreading in Slovakia in 1699 (Lohmeyer and Sukopp, 1992). Pysek and Prach (2003) stated that it was first introduced to the region now known as the Czech Republic in 1835 and first recorded in the wild in 1875. It reached the Brandenburg region of Germany in 1736 (Kowarik, 1992) and the first record in the wild was in 1919, hence a time-lag of 183 years between the species introduction and its spread. In Berlin, the tree was only observed to spread in 1945 (Kowarik, 1992). It was thought to have been introduced to Poland around 1800 (Zajac et al., 1998). In Siberia, A. negundo has been cultivated since at least the 1940s and was planted in the Novosibirsk Botanical Garden in 1954 (Adamowski, 1991). In Australia and New Zealand the spread of A. negundo is recent; for example, in Australia it was only recorded as naturally regenerating in 1987 (Groves and Hosking, 1997; Williams et al., 2002).
Risk of IntroductionTop of page
In Australia, a native alternative to A. negundo is being promoted and more species are to be identified by the horticultural trade (Lewis and Stephens, 2001). In New Zealand, as part of a Conservation Weed Risk assessment it has gained a relatively high score but experts have ranked the species as a minor weed because it has yet to become a conservation weed (Williams et al., 2002).
HabitatTop of page
A. negundo is widespread in riparian and palustrine plant communities and has been reported from a variety of vegetation types in the USA (Rosario, 1988). It is most commonly associated with deciduous forest communities but also occurs in scrub- and grass-dominated vegetation types. In continental Europe it is now common in many urban areas and along many river systems (Sachse, 1991) and in Toronto, Canada it is reported as invading all habitat types (Havinga, 2000). In Europe, A. negundo is invading ecosystems that are now rare and protected such as virgin forest, e.g. Bialowieza in Poland (Adamowski et al., 2002) and riparian reserves (Drescher and Magnes, 2002).
Habitat ListTop of page
|Terrestrial – Managed||Rail / roadsides||Present, no further details||Harmful (pest or invasive)|
|Urban / peri-urban areas||Present, no further details||Harmful (pest or invasive)|
|Terrestrial ‑ Natural / Semi-natural||Natural forests||Present, no further details||Harmful (pest or invasive)|
Hosts/Species AffectedTop of page
Some abandoned pastures, for instance in Poland, are readily colonized by A. negundo (Falinski, 1998). It is an occasional invader of cropland and forested areas including plantations.
Biology and EcologyTop of page
The chromosome number is 2n=26 (Foster, 1933). The sex expression of this dioecious species is believed to be genetically controlled and therefore no sex switching occurs (Dawson and Geber, 1999).
Physiology and Phenology
A. negundo is a fast growing and relatively short lived species with a maximum life span of 100 years but more typically of about 75 years. Sexual dimorphism in A. negundo has long been noticed. Lysova and Khiznyak (1976) reported greater height and stem diameter in male compared to female individuals and Ramp and Stephenson (1983) found that males produced more leaf biomass and females more radial growth. Willson (1986) reported that fruit production had no detectable effect on shoot extension growth of female trees compared to male individuals. Fruiting branches grew less than asexual branches in one year out of two but the degree of incremental growth reduction was independent of fecundity levels. These studies indicated that genders responded differently to water availability leading to a segregation of genders (Dawson and Ehleringer, 1993). However, Ward et al. (2002) demonstrated this was true of wet years, with female individuals exhibiting higher growth rate and being more profligate water users, whereas in dry years both sexes showed similar growth and physiological responses. Increasing precipitation would thus favour female trees and also alter the water flux from riparian ecosystems. Flowers of both male and female trees usually appear in spring well before the leaves. The fruits often persist on the tree well into the winter. In North America, large seed crops are produced annually.
Unlike other species of maples which are all hermaphroditic with a wide array of sex expression, A. negundo is a dioecious species (de Jong, 1976). The sex ratio is variable and often skewed towards males especially on drier ground away from streamsides (Lysova and Khiznyak, 1976; Sachse, 1992; Ward et al., 2002). The tree may start bearing fruit when it is just 5 years old (Sachse, 1992). There are approximately 30,000 seed/kg (Olson and Gabriel, 1974). The tree is both wind-pollinated and wind-dispersed, although dispersal by birds and squirrels also occurs. Vegetative reproduction is common on damaged individuals. Exposed or damaged roots will produce new shoots. Shelterbelt trees whose bole had died as a result of drought have been known to recover by producing root sprouts (Rosario, 1988). Germination under test conditions varies widely from 0 to 96% (Williams and Winstead, 1972; Olson and Gabriel, 1974). In the USA, Williams and Winstead (1972) found that northern populations required shorter stratification periods, germinated at colder temperatures and with a higher germination rate than southern populations. Under natural conditions it regenerates readily on disturbed and moist soils and does tolerate medium shade (Rosario, 1988) but poor establishment or high seedling mortality occurs in dense ground cover or under closed canopy (Sachse, 1992).
A. negundo is generally a temperate species tolerant of a wide range of environmental conditions. It is tolerant to water logging (Howell and Benson, 2000) and is highly sensitive to water stress (Ward et al., 2002), but it is also recognized as a drought-tolerant tree once established (Rosario, 1988). Dawson and Ehleringer (1991) have shown that juveniles depend solely on precipitation or stream water for approximately the first ten years, whereas older trees rely on groundwater. Although often classified as pioneer species (Tickner et al., 2001) it is moderately shade-tolerant (Niinemets, 1998). This fast-growing species is hardy and is resistant to cold (Rosario, 1988). In North America, its upper and lower altitudinal range varies greatly ranging from 680 to 3048 m with a range no greater than 1800 m and usually less than 500 m in any one state (Rosario, 1988). Branches readily break during stormy weather and being thin-barked, trees are readily injured by fire (Rosario, 1988).
As A. negundo favours disturbed ground and higher light intensities it becomes established in the earlier stages of succession.
Latitude/Altitude RangesTop of page
|Latitude North (°N)||Latitude South (°S)||Altitude Lower (m)||Altitude Upper (m)|
Air TemperatureTop of page
|Parameter||Lower limit||Upper limit|
|Absolute minimum temperature (ºC)||0||0|
|Mean annual temperature (ºC)||0||22|
|Mean maximum temperature of hottest month (ºC)||0||0|
|Mean minimum temperature of coldest month (ºC)||0||0|
RainfallTop of page
|Parameter||Lower limit||Upper limit||Description|
|Dry season duration||0||4||number of consecutive months with <40 mm rainfall|
|Mean annual rainfall||400||2000||mm; lower/upper limits|
Soil TolerancesTop of page
- seasonally waterlogged
Notes on Natural EnemiesTop of page
A number of insect pests or fungal diseases have been noted on A. negundo (e.g. Gilman and Watson, 1993) but few have been reported to adversely affect the species. It is susceptible to heartrot and some insect pests but these rarely kill it. The boxelder bug, Boisea trivittata (Say) feeds primarily on seed-bearing trees by sucking sap from the leaves, tender twigs and developing fruits, and although they cause little damage they are a nuisance in dwellings (Vail et al., 2002).
Means of Movement and DispersalTop of page
Natural Dispersal (Non-Biotic)
A. negundo, like all other maple species, is chiefly wind-dispersed. Dispersal in maples is usually localized, no more than 100 m from the seed source, but may occasionally be spread over several kilometres if seeds are released when hard snow lies on the ground and very windy weather prevails (Binggeli, 1992). In riparian systems, samaras are probably also dispersed by water but the importance of this dispersal mechanism is unclear.
Vector Transmission (Biotic)
Limited dispersal by birds and squirrels may occur.
In several parts of the world the tree has been extensively planted in hedges and as a windbreak. The current importance of this practice, and in its introduced range in particular, is unknown.
There is a low risk of accidental introductions.
Because A. negundo is an important ornamental tree species with a number of varieties, nearly all new introductions will be intentional. Even where already present the introduction of new varieties/ecotypes may result in the establishment of weedy strains.
Plant TradeTop of page
|Plant parts liable to carry the pest in trade/transport||Pest stages||Borne internally||Borne externally||Visibility of pest or symptoms|
|Fruits (inc. pods)||fruits|
|True seeds (inc. grain)||seeds|
Impact SummaryTop of page
|Fisheries / aquaculture||None|
ImpactTop of page
No relevant instances are documented, but it has been reported that the tree may be poisonous to livestock (Rosario, 1988).
Environmental ImpactTop of page
Sediment deposition in an A. negundo stand was found to be greater than in native vegetation after a major flood event (8.4 ± 0.4 kg/m² vs 5.8 ± 0.7 kg/m²) (Brunet and Astin, 1997). Other effects of A. negundo on the environment have not been quantified.
Impact: BiodiversityTop of page
No relevant instances are documented. As it becomes a major component of the ecology of European riparian vegetation, its presence will probably result in a shift in species composition reducing the presence of some species. For instance, in France A. negundo is now an important component of the Loire Valley vegetation but its impact on the populations of the re-introduced European beaver is unknown (Fustec et al., 2001).
Social ImpactTop of page
This species does not to have deleterious attributes such as spines or health-inducing risks and as such probably has limited social impacts. However, in the USA the insect Boisea trivittata (Say), after feeding on pistillate trees, over-winters on or near buildings. In spring, when it starts disperse to breed, this largish insect (over 1 cm long), may enter houses in large numbers and stain walls and curtains with brown faecal material. When crushed they produce a foul odour and may bite if handled carelessly (Vail et al., 2002). This harmful social impact has yet to be reported from Europe and other regions where the species has been introduced.
Risk and Impact FactorsTop of page Invasiveness
- Proved invasive outside its native range
- Highly adaptable to different environments
- Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
- Has high reproductive potential
- Damaged ecosystem services
- Ecosystem change/ habitat alteration
- Highly likely to be transported internationally deliberately
UsesTop of page
Little economic use is made of this species as its timber has undesirable characteristics, being light, soft, close grained and of low strength. Locally, the wood may be used to make boxes and in rough construction, but it is only occasionally used to produce cheap furniture and other wooden products. Formerly, the wood was used for posts, fencing and fuel. However, it is a poor fuel as the wood is soft and spongy (Rosario, 1988). In North America, the foliage of A. negundo has poor nutritional value for livestock. It is a browse species of secondary importance to deer whereas the seeds are an important food source for birds and squirrels. It has a good value as cover for both wildlife and livestock and has been used to revegetate riparian areas (Rosario, 1988).
Uses ListTop of page
- Shade and shelter
Wood ProductsTop of page
- Roundwood structures
Similarities to Other Species/ConditionsTop of page
If no fruiting material is observable, the species, because of its mainly pinnate foliage, could be readily ascribed to a genus other than Acer. However, when present, the distinct samaras clearly indicate that the species belongs to the maple (Aceraceae) family.
Prevention and ControlTop of page
To date, little effort has been undertaken to control this species although its control has been advocated, for instance in Austria (Drescher and Magnes, 2002). No information is available for cultural, chemical or mechanical control although cutting and stump treatments used on other tree species may prove effective. A. negundo has not been considered for biological control though numerous insect pests are recorded on the species. The use of male trees only in amenity planting would eliminate risks of spread in the introduced range.
ReferencesTop of page
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Adamowski W, 1991. Naturalization of Acer negundo in the environs of Novosibirsk (West Siberia). Phytocoenosis, 3:41-42.
Adamowski W; Dvorak L; Ramanjuk I, 2002. Atlas of alien woody species of the Bialowieza Primaeval Forest. Phytocoenosis, 14:1-304.
Anon., 1963. Native trees of Canada. Bulletin No. 61. Ottawa, Canada: Department of Forestry.
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Brunet R-C; Astin KB, 1997. Spatio-temporal variations in sediment nutrient levels: the River Adour. Landscape Ecology, 12:171-184.
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Lysova NV; Khiznyak NI, 1976. Sex differences in trees in the dry steppe. Soviet Journal of Ecology, 6:522-527.
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Mosyakin SL; Yavorska OG, 2002. The nonnative flora of the Kiev (Kyiv) Urban Area, Ukraine: a checklist and brief analysis. Urban Habitats, 1:3-23. http://www.urbanhabitats.org/v01n01/nonnativekiev_pdf.
Niinemets U, 1998. Adjustment of foliage structure and function to a canopy light gradient in two co-existing deciduous trees. Variability in leaf inclination angles in relation to petiole morphology. Trees Structure and Function, 12:446-451.
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Török K; Botta-Dukát Z; Dancza I; Németh I; Kiss J; Mihály B; Magyar D, 2003. Invasion gateways and corridors in the Carpathian Basin: biological invasions in Hungary. Biological Invasions, 5:349-356.
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Vail, K. , Klingeman W, Williams H, 2002. Boxelder bugs and red-shouldered bugs. Agricultural Extension Service, The University of Tennessee SP341-H. www.utextension.utk.edu/publications/spfiles/SP341-H.pdf.
Ward JK; Dawson TE; Ehleringer JR, 2002. Responses of Acer negundo genders to interannual differences in water availability determined from carbon isotope ratios of tree ring cellulose. Tree Physiology, 22:339-346.
Webb CJ; Sykes WR; Garnock-Jones PJ, 1988. Flora of New Zealand Volume IV. Naturalised Pteridophytes, Gymnosperms and Dicotyledons. Christchurch, New Zealand: DSIR Botany Division, 1365 pp. http://floraseries.landcareresearch.co.nz/pages/Book.aspx?fileName=Flora%204.xml
Williams RD; Winstead JE, 1972. Population variation in seed germination and stratification of Acer negundo L. Transactions of the Kentucky Academy of Science, 33:43-48.
Willson MF, 1986. On the cost of reproduction in plants: Acer negundo. American Midland Naturalist, 115:204-207.
Zajac A; Zajac M; Tokarska-Guzik B, 1998. Kenophytes in the flora of Poland: list, status and origin. In: Falinski JB, Adamowski W, Jackowiak B, eds. Synathopization of plant cover in new Polish research. Phytocoenosis, 10:107-116.
Distribution MapsTop of page
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