When does black walnut bloom?

Black walnut typically flowers in May and June, producing separate male catkins and small female flower clusters on the same tree.

What light conditions does black walnut need?

Black walnut grows best in full sun but tolerates part sun and part shade, especially as a young tree before the canopy fills in.

How much water does black walnut require?

This tree does well with medium soil moisture and has a deep taproot that allows it to handle drier periods once established.

What insects are associated with black walnut flowers?

Bees and beetles have been observed visiting black walnut flowers, though the tree also relies heavily on wind for pollen dispersal.

What kind of growth form does black walnut have?

Black walnut is a single trunked tree that can reach large heights and develops a broad, rounded crown at maturity.

Is Black Walnut toxic to dogs?

Yes. Black Walnut is listed as toxic to dogs by the ASPCA Animal Poison Control Center (aspca.org). If your pet has been exposed, call the ASPCA Animal Poison Control Center at (888) 426-4435.

Is Black Walnut toxic to cats?

Black Walnut is not on the ASPCA Animal Poison Control Center toxic plant list for cats (aspca.org).

Is Black Walnut toxic to livestock?

Black Walnut is listed as toxic to grazing livestock such as cattle, sheep, and goats (slight severity) by the USDA PLANTS Database. This is separate from pet (dog and cat) toxicity.

Is Black Walnut HOA-friendly?

Black Walnut takes more care to look intentional in a front yard. Consider it for backyard or mid-zone beds rather than the street edge.

Black Walnut

Name: Pollinator Patch
Author: Pollinator Patch

Juglans nigra

Last reviewed: September 2026

Black walnut is a large deciduous tree that blooms in May and June and grows well in part shade with medium moisture, often found along river valleys and mixed hardwood forests across the central and eastern United States.

Black Walnut (Juglans nigra) — Photo: Chris Light

Black Walnut is toxic to dogs.

Listed as toxic by the ASPCA Animal Poison Control Center (opens in new tab) (last reviewed 2026-05-21). If your pet has been exposed, call the ASPCA Animal Poison Control Center at (888) 426-4435and your veterinarian's emergency line.

Pollinator Patch flags toxic plants so you can choose a pet-safe native alternative for your yard.

Black Walnut is listed as toxic to grazing livestock (cattle, sheep, and goats) at a slight level by the USDA PLANTS Database (opens in new tab). This is a livestock indicator and is separate from pet toxicity.

Light

part shade

Water

medium

Size

300"–600" H × 300"–600" W

Bloom

May, Jun

Native to

AL, AR, CT, DE and 29 more states

Pollinators

bees, beetles

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Black walnut is a large native shade tree that can reach 25-50 feet tall with an equally wide canopy. It produces edible nuts in fall and has distinctive compound leaves that turn yellow in autumn. The tree is allelopathic, meaning it releases chemicals that can inhibit the growth of many other plants nearby.

Growing Black Walnut

Grow Black Walnut in part shade and medium water. Mature plants reach 300 to 600 inches tall and spread 300 to 600 inches wide. Expect high maintenance to keep it looking intentional in a front yard.

In an HOA neighborhood

Black Walnut takes more care to keep looking intentional in a front yard. Maintenance level: high. Consider it for backyard or mid-zone beds rather than the street edge.

Works well in: backyard only.

Extremely large size inappropriate for most residential lots
Drops messy nuts and leaves requiring constant cleanup
Allelopathic properties can damage nearby ornamental plants

Wildlife value

Host plant for luna moth, viceroy butterfly, banded tiger moth.

Black walnut supports bees and beetles during its spring bloom period. The nuts provide food for squirrels, chipmunks, and other wildlife throughout fall and winter.

Common questions

When does black walnut bloom?: Black walnut typically flowers in May and June, producing separate male catkins and small female flower clusters on the same tree.
What light conditions does black walnut need?: Black walnut grows best in full sun but tolerates part sun and part shade, especially as a young tree before the canopy fills in.
How much water does black walnut require?: This tree does well with medium soil moisture and has a deep taproot that allows it to handle drier periods once established.
What insects are associated with black walnut flowers?: Bees and beetles have been observed visiting black walnut flowers, though the tree also relies heavily on wind for pollen dispersal.
What kind of growth form does black walnut have?: Black walnut is a single trunked tree that can reach large heights and develops a broad, rounded crown at maturity.
Is Black Walnut toxic to dogs?: Yes. Black Walnut is listed as toxic to dogs by the ASPCA Animal Poison Control Center (aspca.org). If your pet has been exposed, call the ASPCA Animal Poison Control Center at (888) 426-4435.
Is Black Walnut toxic to cats?: Black Walnut is not on the ASPCA Animal Poison Control Center toxic plant list for cats (aspca.org).
Is Black Walnut toxic to livestock?: Black Walnut is listed as toxic to grazing livestock such as cattle, sheep, and goats (slight severity) by the USDA PLANTS Database. This is separate from pet (dog and cat) toxicity.
Is Black Walnut HOA-friendly?: Black Walnut takes more care to look intentional in a front yard. Consider it for backyard or mid-zone beds rather than the street edge.

These answers were drafted with an AI model from this plant's data. Verify care details with a local expert.

Native range data from vouchered herbarium specimen records and regional native plant society lists. Pollinator and host plant associations compiled from GBIF, iNaturalist, and published ecological literature.

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