Flora of New Zealand Series

Japanese walnut

Widespreading tree to c. 15 m high. Shoots with glandular hairs; lf scars not prominent. Buds brown-tomentulose. Lvs to c. 60 cm long; petiole and rachis to c. 40 cm 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 × 3-8 cm, oblong or oblong-ovate. ♂ catkins to c. 15 cm long, with glandular hairs. ♀ catkins 9-22-flowered, ± tomentose with purplish glandular hairs; stigmas 6-7 mm long, prominent, pink. Fr. 2.5-4 cm long, broad-ovoid, beaked, viscid, tomentose, ferrugineus. Shell rugose, thick, ± subcordate at base; sutures thick and raised, dividing with difficulty; beak often sharply acute. Seed convoluted.

N.: N. Auckland (north side of the Hokianga), Auckland, Bay of Plenty, Waikato, Waitomo State Forest, Raglan, near Rotorua (Te Mu), Levin.

Japan, Sakhalin 1983

An escape from cultivation around settlements.

FL Oct-Nov.

Japanese walnut is cultivated in many parts of N.Z., especially in the Bay of Plenty, Waikato and Auckland areas. Seedlings sometimes occur in large numbers in the vicinity of parents. Some cultivated trees in N.Z. approach var. cordiformis (Maxim.) Rehder, heartnut, a thin-shelled var. with a broad-cordate base, but this var. has not been collected wild. The sp. has been previously known in N.Z. as J. sieboldiana.