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COSEWIC assessment and status report on the Butternut in Canada

COSEWIC Status Report
on the
Butternut
Juglans cinerea
in Canada
2003

Species Information

Name and Classification

Scientific name:
Juglans cinerea
Common names:
butternut, white walnut, lemonnut, oilnut, noyer cendré
Family:
Juglandaceae (walnut family)
Major plant group:
dicot flowering plant



Description

Butternut is a small to medium-sized tree with a broad spreading irregularly shaped crown. It is seldom more than 30 metres in height and 90 cm in diameter at maturity (Rink, 1990). Unless soils are shallow, a taproot is common, along with numerous deep, widespread lateral roots (Harlow et al., 1979). The leaves are pinnately compound with 11-17 leaflets between 9 to15 cm long (Landowner Resource Centre, 1997) that are opposite and almost stalkless (Farrar, 1995). Leaves are yellowish-green and densely hairy on the underside (Farrar, 1995). Twigs are stout, hairy, and yellowish orange in colour (Farrar, 1995) with a chambered pith (Hosie, 1979). The terminal bud is elongated, about 1.0 to 1.5 cm long, somewhat flattened and blunt tipped with lobed outer scales (Farrar, 1995). Lateral buds are much smaller and rounded, often with more than one bud above the leaf scar (Hosie, 1979). The upper margin of the leaf scars are flat and bordered with hair (Farrar, 1995). On younger trees, the bark is grey and smooth while older individuals have bark that becomes separated by narrow, dark fissures into wide, irregular, flat-topped, intersecting ridges (Farrar, 1995). The ovoid fruit is a single-seeded nut with the husk covered with a dense layer of short sticky hairs and an inner shell with jagged ridges.

The species is distinguished from the similar black walnut by such characteristics as its hairy twigs and leaves, terminal leaflet that is as large as the lateral leaflets, and ovoid hairy fruit with jagged ridges on the shell of the nut. In contrast, black walnut has smooth or only slightly hairy twigs and leaves with the terminal leaflet missing or smaller than the lateral ones; the fruit is globular, nearly hairless, and has rounded ridges on the surface of the shell.