Juglans ailantifolia
NPPA pest plant
Environmental Weed (2024)
Common names
Japanese walnut
Biostatus
Exotic
Category
Vascular
Structural class
Trees & Shrubs - Dicotyledons
Flower colours
Red/Pink, Violet/Purple
Detailed description
Widespreading tree to around 15m high. Shoots with glandular hairs; leaf scars not prominent. Buds brown-tomentulose. Leaves to approx. 60cm long; petiole and rachis to about 40cm long, densely clothed in glandular hairs. Leaflets 9~17, sessile or nearly so, becoming glabrous or nearly so above, densely hairy with simple and stellate hairs on the veins beneath and midrib glandular, serrulate with teeth often sparse; base obliquely truncate or subcordate; apex acute to acuminate; lowest pair of leaflets often smaller; terminal leaflet mostly of similar size to lateral leaflets. Lamina of terminal leaflet 6~18 x 3~8cm, oblong or oblong-ovate. Male catkins to around 15cm long, with glandular hairs. Female catkins 9~22-flowered, generally tomentose with purplish glandular hairs; stigmas 6~7mm long, prominent, pink. Fruit 2.5~4cm long, broad ovoid, beaked, viscid, tomentose, ferrugineus. Shell rugose, thick, usually subcordate at base; sutures thick and raised, dividing with difficulty; beak often sharply acute. Seed convoluted. (- Webb et. al., 1988)
Habitat
Terrestrial.
Conservation status
Not applicable
Detailed taxonomy
Family
Juglandaceae
Ecology
Flowering
October, November
Year naturalised
1983
Origin
Japan
Reason for introduction
Ornamental
Life cycle and dispersal
Perennial.
Other information
National Pest Plant Accord species
This plant is listed in the 2020 National Pest Plant Accord. The National Pest Plant Accord (NPPA) is an agreement to prevent the sale and/or distribution of specified pest plants where either formal or casual horticultural trade is the most significant way of spreading the plant in New Zealand. For up to date information and an electronic copy of the 2020 Pest Plant Accord manual (including plant information and images) visit the MPI website.
Environmental Weed (2024)
This plant is named in a list of 386 environmental weeds in New Zealand 2024 prepared by DOC. 759 candidate species were considered for inclusion on this new comprehensive list of environmental weeds in New Zealand. The species considered were drawn from published lists of weed species, lists of plants that must be reported or managed by law if observed, existing national and regional programmes and agreements for pest management, and species already managed by the Department of Conservation (DOC). Candidate species were then assessed to see if they were fully naturalised and whether they have more than minor impacts in natural ecosystems. Read the full report here.