Quick Facts

Quick facts

• Box Elder (Acer negundo) is a small to medium sized, often multi-stemmed, deciduous tree that can grow to 20 m but is commonly only 8 m tall.
• It has characteristic V-shaped fruiting bodies (made up of two linked winged fruits) that spin like propellers when they fall to the ground.
• Various cultivars and varieties are available, including white-variegated forms.
• It was introduced as an ornamental and has been widely cultivated in parks, streets and home gardens.
• It has become an invasive weed, especially on riverbanks and in moist forests and disturbed areas in damp soils.
• It is a riparian weed in temperate zones and has the potential to spread to many similar areas.

What Does It Look Like?

What is it?

Box Elder (Acer negundo) is a small to medium, slender, deciduous, often multi-stemmed, tree that can grow up to 20 m high (but mostly only to about 8 m high in weedy situations) It has smooth light grey or grey-brown bark (becoming fissured or flaky with age) and an open, irregular, broad crown. The large leaves are mostly 20–30 cm long, divided into  3–7 (sometimes 9) leaflets that are oval to egg shaped or lance shaped. The petiole or leaf stalk is 5–12 cm long. Leaves may be entirely green or white-variegated, and turn yellow before falling in autumn. Variegated forms of Box Elder revert to wholly green-leaved plants in the wild (Walsh 1999), including the often planted Acer negundo 'Variegatum' that has broad white-margined leaves (Blood 2001).

Flower heads appear before or with the leaves and usually has male and female flowers on different plants. The small flowers are greenish, yellowish green or sometimes pinkish, either male or female, and lack petals. Male flowers hang in clusters, while female flowers occur along a drooping branched stalk.

The dry, winged fruits (called samaras) are pale yellowish green, turning pale brown, 3–4 cm long, with the yellowish wing strongly veined. 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 (Coombes 1992; Walsh 1999; Blood 2001; Sainty and Associates 2001; Wilson 2002; Weber 2003; Richardson et al. 2006).

For further information and assistance with identification of Box Elder contact the herbarium in your state or territory.

Flower colour

Yellow, Green, Pink

Growth form (weed type/habit)

Tree

Where it currently grows? Preferred habitat

Box Elder is widely cultivated and grows best in cooler areas. It tolerates frost, full sun, shade (once established), air pollution and flooding, as well as drought to some extent. The tree has become invasive along watercourses and in wet forests and woodlands, as well as roadsides and other disturbed open sites with moist soil (Carr et al. 1992; Hosking 1997; Blood 2001; Sainty and Associates 2001; Wilson 2002; Weber 2003; Richardson et al. 2006).

Are there similar species?

Sycamore Maple (Acer pseudoplatanus), a native of Europe where it is also sometimes naturalised, differs from Box Elder in having simple lobed leaves (with 3–5 lobes) and growing to a larger size (to 30 m high) (Wilson 2002). Other introduced species of Acer (the maples), as well as species of Fraxinus (the ashes), with compound (divided into leaflets) leaves, may also be confused with Box Elder. Ashes have single-winged fruits, while those of maples are arranged in pairs forming a V-shaped propeller-like fruiting body (Kodela 2008 pers. comm.).

Why Is It A Weed?

What are its impacts?

Native ecosystems: Box Elder is a fast growing species that invades bushland and is a serious weed in riparian environments (e.g. along watercourses) and sheltered moist forests (Carr et al. 1992; Hosking 1997; Sainty and Associates 2001; Richardson et al. 2006). It crowds and shades out native plants in sensitive bushland along watercourses, and has become a major riparian weed of a some waterways. It is also thought that dense long-term infestations of this species may cause significant damage to waterways by trapping sediment, causing erosion and depleting oxygen levels in the water as a result of shedding large quantities of autumn leaves. It is a successful and persistent invader once established, displacing native shrubs and trees and preventing their regeneration (Weber 2003). Box Elder is quick growing and out-competes other vegetation, mainly by shading, its extensive root system, and creation of a heavy leaf-fall (Blood 2001).

Urban areas: Also a weed in amenity areas and park and gardens, and can come up en-mass in garden beds. The root system seeks water and can invade pipes (Blood 2001). 

How does it spread?

Box Elder is spread by seed in the prolifically produced winged fruits that may be carried by wind and moving water. It can also be spread by dumped garden waste, and by seeds in chipped pruning used as mulch (Blood 2001). Box Elder re-sprouts after damage and forms root suckers (Weber 2003).

What is its history in Australia?

Box Elder was introduced as an ornamental tree, being widely planted in parks, gardens and streets. The earliest records of it being naturalised in Australia are from riverbanks of the Nepean River in the Sydney area from about 1959 onwards. It appears to have become naturalised around Armidale, New South Wales, before 1975 (Hosking 1997; National Herbarium of New South Wales 2007). The earliest cultivated herbarium record is from New South Wales in 1936 (AVH 2021).

How To Manage It?

Best practice management

Prevention: The best control of Box Elder is to avoid planting it, especially in parks and gardens adjacent to or near natural areas with riverbanks, moist gullies and wet forest or woodland (Kodela 2008 pers. comm.).

Non-chemical control: Hand removal of seedlings and small trees has proven successful. 

Chemical control: Established trees can be cut at ground level and the cut stems treated with herbicides, while seedlings and saplings can be hand pulled or dug out (Weber 2003). Use the cut and paint method or stem injection.

See the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

Box Elder is a deciduous tree that flowers and produces leaves in spring. Flowering (from early September) usually occurs before leaf growth. Fruits persist on the plant until, or during, winter. Mass germination of seed occurs in spring, and this can form extensive carpets of seedlings (Coombes 1992; Blood 2001).

Where Is It Found?

Which states and territories is it found?

ACT, NSW, QLD, SA, VIC, WA

What areas within states and territories is it found?

Box Elder is widely cultivated in southern Australia. It is occasionally naturalised in New South Wales, especially in cooler districts such as the tablelands, but also in the Sydney region, and in the Australian Capital Territory around Canberra (Wilson 2002; National Herbarium of New South Wales 2007). 

There are scattered populations in southern and north-eastern parts of Victoria, for example, along the Plenty River in the outer Melbourne metropolitan area (Walsh 1999). 

In south-eastern South Australia (Barker et al. 2005) it is founded in the higher rainfall ares in the Adelaide hills and Mid north, Fleurieu Peninsula and the wetter southern part of Eyre peninsula 

It is possibly naturalised in south-eastern Queensland (Bostock 2008 pers. comm.).

In Western Australia found around Perth and the south-east (AVH 2021).

Where does it originate?

Box Elder is native to North America where it is commonly found in riparian forests, on riverbanks and floodplains, usually in moist soil (Coombes 1992; Wilson 2002; Weber 2003).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

ACT

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Acer negundo

Other scientific names (synonyms)?

Does it have other known common name(s)?

Box Elder Maple, Ash-leaved Maple, Black Maple