Black Walnut.

At a glance

Care level

Easy

Plant type

Deciduous tree

Light

Full sun

Indoor light

Direct sun

Water

Every 7 to 14 days

Mature size

100 feet

Growth rate

Medium

Hardiness

USDA 4 to 9

Bloom time

Mid to late spring

Care

Plant this tree in a location with plenty of space to accommodate its large canopy and root system. Keep an eye out for signs of thousand cankers disease or walnut twig beetle activity. Ensure the soil remains moist but well drained for the best nut production.

Watering

Young trees need consistent moisture until they are well established.

Feeding

Apply a balanced fertilizer in early spring if the tree shows signs of slow growth.

Pruning

Prune during the dormant season to remove dead or crossing branches.

Repotting

This species is a large tree and is not suitable for container cultivation.

Soil

Deep, rich, moist, well drained soil

Soil pH

6.0 to 7.5

Temperature

-35 to 35°C

Humidity

40 to 70%

Safety

People

The husks and roots contain juglone, which can cause skin irritation in sensitive individuals.

Pets

Moldy hulls and nuts can carry tremorgenic mycotoxins that cause tremors and seizures in dogs if eaten, so keep dogs away from fallen, decaying nuts.

Children

The heavy, falling nuts can pose a risk of injury to small children if they are playing under the tree during harvest season.

Contact allergens

Contact with the green husks may cause dermatitis in some people.

Airborne allergens

Pollen from the male catkins can trigger seasonal allergies in sensitive individuals.

Edibility

The green husks can stain skin and clothing, and nuts must be thoroughly dried and cleaned before consumption.

How to identify it

• Deeply furrowed, dark brown bark
• Compound leaves with many leaflets
• Large, round, green husked nuts
• Strong, distinct spicy fragrance

Height

20 to 40m

Spread

15 to 30m

Leaves

green, yellow, deciduous

Flowers

green, yellow, 0.5 to 1cm

Fruit

green, brown, Autumn

Problems to watch for

• Thousand Cankers Disease · A fungal disease spread by the walnut twig beetle that causes branch dieback.
• Walnut Caterpillar · Larvae can defoliate branches during the summer months.

Growing it

Propagation

seed

When to plant

Spring, Autumn

Choose plants that are known to be juglone tolerant to fill the space under the canopy.

Grows well with

• Black Raspberry · This berry is one of the few plants that can tolerate the juglone produced by the walnut.
• Daylily · Daylilies are generally resistant to the allelopathic effects of the walnut tree.

Keep away from

• Tomato · Tomatoes will wilt and die if planted within the root zone of a black walnut.
• Apple · Apple trees often suffer from stunted growth or death when planted near black walnuts.

Similar species

• Butternut · It is a smaller relative with longer, more oblong nuts.

Science

Family

Juglandaceae

Genus

Juglans

Order

Fagales

Class

Magnoliopsida

Native range

Eastern and Central North America

Conservation

This species is not currently endangered, but it is often harvested for its valuable timber.

It is a fast growing tree that thrives in deep, moist, well drained soils along river valleys.

Value to wildlife

food source for squirrels, nesting habitat

Pollinators

bees, beetles

Uses

timber production, nut production, shade tree, wildlife habitat

Taxonomy resolved against GBIF.

Questions people ask

Can I grow vegetables under a black walnut?

Most vegetables, especially tomatoes and peppers, will not grow well due to the juglone in the soil.

How long until it produces nuts?

Trees typically begin producing nuts when they are 10 to 15 years old.

Where the name comes from

The name nigra refers to the dark color of the heartwood, while Juglans is the Latin name for walnuts.

Good to know

• Black walnut wood is highly prized for furniture and gunstocks.
• The roots can extend far beyond the canopy, affecting sensitive plants nearby.
• Native Americans used the husks to create a dark brown dye.
• The nuts are a favorite food for squirrels and other rodents.