Maryland Native Keystone Plants
Juglans nigra – Black Walnut
Juglans nigra, known as Black Walnut, is a common native tree of eastern North America. Reaches a height of 75 feet as well as a 75-foot spread of its branches, though it will grow thinner and taller in a forested area, reaching a maximum height of 150 feet. Dark gray bark with a ridged diamond pattern. Leaves are alternate, pinnately compound and have 13-23 leaflets. Flowers are insignificant and bloom in spring, being pollinated by themselves or by the wind. Black walnut trees begin producing walnuts within 12 to 15 years. Drops walnuts shortly after their leaves fall in autumn. Distinctive, spicy odor comes from the crushed leaves, stems, and walnut shells.
What makes this a Keystone Plant? 125 Lepidoptera species use Juglans species as a host plant.
Black Walnuts have significant wildlife value. Walnuts are an important source of food for the Eastern Fox Squirrel, woodpeckers, flying squirrels, and some other species of birds. Over 125 Lepidoptera feed on the leaves, such as Has been recorded as a host plant for the Banded Hairstreak, Luna Moth, Regal Moth, Imperial Moth, Walnut Sphinx Moth, Fall Webworm Moth, Walnut Caloptilia, Pecan Leafminer Moth, Monkey Slug Moth, Skiff Moth, Sad Underwing Moth, Bride Underwing Moth, Penitent Underwing Moth, Yellow-gray Underwing Moth, Widow Underwing Moth, Banded Tussock Moth, Angus’s Datana Moth, Walnut Caterpillar Moth, Red-humped Caterpillar Moth, Black-blotched Prominent Moth, Closebanded Yellowhorn Moth, Walnut Shoot Moth, Pecan Leaf Casebearer Moth, American Plum Borer, Hickory Shuckworm Moth, Pecan Bud Moth, Gray-edged Bomolocha Moth, Sleeping Baileya Moth, and Small Baileya Moth. Eastern screech-owls use the limbs of black walnut trees for roosting.
Juglone Information
Unfortunately, Black Walnuts have a bad reputation because they release a chemical (juglone) into the soil to suppress growth of plants in its immediate vicinity, but many of our native plants are tolerant of this chemical. In fact, many plant species release chemicals to help slow other plant growth and helping them get an edge. Check out this list of tolerant plants published by Penn State Extension: link (Some of the plants on this list are non-native and we would not recommend them).
Other Information
Besides being great wildlife trees, Black Walnuts are edible for humans and provide more nutrients than English Walnuts! We also carry Juglans cinerea, or Butternut.
Plant Information
Common Name: Black Walnut
Type: Tree
Family: Juglandaceae
Height: 50.00 to 75.00 feet
Spread: 50.00 to 75.00 feet
Bloom Time: May to June
Bloom Description: Yellowish-green
Sun: Full sun
Water: Medium
Maintenance: Medium
Suggested Use: Shade Tree
Flower: Insignificant
Leaf: Fragrant
Fruit: Showy, Edible
Tolerate: Rabbit, Drought
(Information from North Carolina Extension and US Forest Service)