Juglans ailantifolia
NPPA pest plant
Common name
Japanese walnut
Family
Juglandaceae
Flora category
Vascular – Exotic
Structural class
Trees & Shrubs - Dicotyledons
Conservation status
Not applicable
Habitat
Terrestrial.
Features
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)
Flowering
October, November
Flower colours
Red/Pink, Violet/Purple
Life cycle
Perennial.
Year naturalised
1983
Origin
Japan
Reason for introduction
Ornamental
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.