Common name: Box-elder Maple, Box Elder, Ash-leaved Maple
Acer negundo L. APNI* 
Description: Small to medium, often multi-stemmed, deciduous tree to 20 m high (in weedy situations mostly recorded to c. 8 m high); usually dioecious. Bark light grey or grey-brown, becoming fissured or flaky with age; canopy open, irregular, broad.
Leaves pinnately compound, mostly 20–30 cm long; leaflets usually 3–7 (sometimes 9), elliptic to ovate or lanceolate, lateral leaflets (3-)4–12 cm long, 2–4.5 cm wide, terminal leaflet larger (to 15 cm long and 8 cm wide) and with longest petiolule, margins regularly to irregularly coarsely toothed or ± lobed, entirely green or white-variegated (there are many ornamental variegated cultivars), turning yellow before falling; veins on lower surface finely hairy; petiole 5–12 cm long.
Inflorescences appearing before or with the leaves, axillary. Flowers greenish, yellowish green or sometimes pinkish, unisexual, lacking petals and disc; pedicels slender; male flowers clustered and pendent; females flowers in raceme-like inflorescences.
Samaras erect, 3–4 cm long; wing strongly veined, yellowish. Two samaras are fused together at their bases to form a V-shape and these fruits spin like propellers when they fall to the ground.
Flowering: spring.
Distribution and occurrence: Widely cultivated, occasionally naturalised, especially in cooler districts (e.g. around Canberra and the tablelands); also in the Sydney region. Native of America. Acer negundo tolerates frost, full sun, shade (once established), air pollution and flooding, as well as drought to some extent. It has become an invasive weed along watercourses (e.g. in riparian vegetation on riverbanks) and in wet forests and woodland, as well as along roadsides and other disturbed open sites with moist soil.
NSW subdivisions: *CC, *NT, *SWS, *ST
Other Australian states: *Vic. *S.A.
Formerly in Aceraceae. Box-elder Maple was introduced as an ornamental tree, being widely planted in parks, gardens and streets. The possible earliest records of it being naturalised in Australia are from riverbanks of the Nepean River in the Sydney Basin, from c. 1959 onwards. It appears to have been naturalised around Armidale prior to 1975. Acer pseudoplatanus (Sycamore Maple), a native of Europe, is also sometimes naturalised but differs from A. negundo in having simple, palmately lobed leaves (with 3-5 lobes). Fraxinus species (the ashes), with compound leaves, differ from Acer (the maples) in having single samaras, i.e. the single-winged fruits are not fused as they are in Acer where they are arranged in pairs forming a V-shaped fruiting body. See also Weeds in Australia profile compiled by P.G. Kodela (2008).
Text by Peter G. Wilson (2002); revised by P.G. Kodela (Feb 2008)
Taxon concept: Flora of NSW 2, revised edn (2002)
APNI* Provides a link to the Australian Plant Name Index (hosted by the Australian National Botanic Gardens) for comprehensive bibliographic data
***The AVH map option provides a detailed interactive Australia wide distribution map drawn from collections held by all major Australian herbaria participating in the Australian Virtual Herbarium project.
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