WSU Clark County Extension
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Black Walnut

Scientific name: Juglans nigra
Taxonomy
Family:Juglandaceae
Type:Deciduous tree
Native:NO
Plant Requirements
Zone:4 to 9
Sun:Full to partial sun
Moisture:Dry
Plant Characteristics
Height:75 ft
Width:50 ft
Bloom:Spring flowers
Bloom Time:May
Bloom Color:Yellow
Additional Characteristics
Trees


Fruit

Leaves


Bark
Wildlife value

Poisonous
Description Famous for its use in the cabinet and flooring trade, Black Walnut is a large deciduous shade tree native to the eastern United States.

  Morphology:
Black Walnut is a broadleaf deciduous tree which grows to a height of 75’ and spread of 50’. It hosts a forked, long trunk with an oval to rounded crown.

Leaves are arranged in an alternate fashion, in a large (1’-2’ long) compound pinnate fashion. Typically each leaf consists of 15 leaflets, though this number can vary from 11 all the way to 23. Each leaflet is 2”-3” long, 1”-2” wide, ovate-oblong in shape with an acuminate tip, and a rounded base. The leaflet margins have serrate edges. When crushed the leaves give off a pleasing fragrance.

Male flowers consist of drooping catkins 3”-5” long. Female flowers appear at the terminal ends of twigs in clusters of two to five, ripening in the autumn into a fruit (nut) with a brownish-green, semi-fleshy husk and a brown corrugated nut. The whole fruit, including the husk, drops to the ground in October. The seed inside the husk is a very hard nut with edible meat within. Both humans and squirrels find the nuts delicious!

The bark on a mature tree is dark brown to grayish black, and is divided by deep, narrow furrows.

  Adaptation:
This tree requires full sun in order to thrive. It does best on deep, rich, moist soils, but does tolerate dry soils. The roots and decaying leaves of this species give off juglone, which inhibits the growth of a wide array of garden plants beneath the plant’s canopy.

This tree is used for parks and other large landscape areas. It is not all that suitable for small yards and boulevards because of its large size and messy fruit.

  Pests:
Generally pest free in the Pacific Northwest.
For assistance, contact Dr. Charles Brun (brunc@wsu.edu), (360) 397-6060 5701
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