Japanese walnut is a deciduous tree up to 15 m high. Its wide spreading foliage limits the growth of other plants.
Japanese walnut is an environmental weed that grows in dense stands. It:
Japanese walnut is a deciduous tree that can grow up to 15 m tall. It has spreading branches that produce a wide canopy up to 15 m. It can live for over 50 years.
Leaves are up to 90 cm long and made up of 4–8 pairs of opposite leaflets with a single leaflet at the end. Leaflets are:
Each tree has both male and female flowers.
Male flowers are:
Female flowers are:
Japanese walnut looks very similar to other walnuts:
It also looks similar to these weed species:
Japanese walnut has been grown as an ornamental tree.
It is a weed around Mt Irvine in the Blue Mountains in the Greater Sydney region. In 2021 plants were found north west of Port Macquarie on the North Coast and these plants are under an eradication program.
It is native to Japan. It has become a weed in New Zealand.
Japanese walnut can grow in a range of soils though it prefers moist well drained soils. It grows best in sunny sites and is frost tolerant. It can grow:
Seeds are spread by water, animals and by people dumping garden waste containing nuts.
Native Plant Trust USA (2021) Go Botany: Dichotomous Key, Juglandaceae, Juglans retrieved 12 April 2021 from: https://gobotany.nativeplanttrust.org/dkey/juglans/#c1,c2
nzflora. Weed Factsheet Juglans ailantifolia. Retrieved 12 April 2021 from: http://www.nzflora.info/factsheet/Weed/Juglans-ailantifolia.html
PFAF Plants for a future. Juglans ailanthifolia - Carrière. Retrieved 12 April 2021 from: https://pfaf.org/user/Plant.aspx?LatinName=Juglans+ailanthifolia
PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved 12 April 2021 from: https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Juglans~ailantifolia
Rietveld, W. J. (1983). Allelopathic effects of juglone on germination and growth of several herbaceous and woody species. Journal of Chemical Ecology, 9(2), 295-308.
Weedbusters New Zealand (2017). Weed Information Sheet Japanese Walnut Juglans ailantifolia. Retrieved 12 April 2021 from: https://www.weedbusters.org.nz/what-are-weeds/weed-list/japanese-walnut/pdf/?nocache=1
If you suspect you have found Japanese walnut contact you local council weeds officer.
Small plants can be hand pulled year-round.
Apply herbicide mixed with diesel to cover the lower stem, all the way around.
Cut the stem and then thoroughly cover the cut stem with herbicide within 15 seconds.
Drill or make cuts into the sapwood and fill with herbicide within 15 seconds.
See Using herbicides for more information.
PERMIT 9907 Expires 31/03/2025
Fluroxypyr 200 g/L
(Comet® 200 herbicide)
Rate: 35 mL per L diesel/kerosene
Comments: Basal bark
Withholding period: Do not graze failed crops and treated pastures or cut for stock feed for 7 days after application. See label for further information.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate
PERMIT 9907 Expires 31/03/2025
Fluroxypyr 333 g/L
(Starane⢠Advanced)
Rate: 21 mL per L diesel/kerosene
Comments: Basal bark
Withholding period: Do not graze failed crops and treated pastures or cut for stock food for 7 days after application. See label for more information.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate
PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L
(Various products)
Rate: One part product to 1.5 parts water
Comments: Cut stump, drill, frill axe or injection
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate
PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L
with Metsulfuron-methyl 600 g/kg (Various products)
Rate: 1:1.5 glyphosate to water + 1 g metsulfuron to 1 L water
Comments: Stem injection
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate
The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.
Area | Duty |
---|---|
All of NSW | General Biosecurity Duty All pest plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable. |
North Coast |
Regional Recommended Measure* (for Regional Priority - Eradication)
Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found. |
*To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfil the general biosecurity duty for this weed click here |
Reviewed 2023