How to identify walnut and butternut

Black walnut (*Juglans nigra*) and butternut (*Juglans cinerea*) are the two native walnuts of eastern North America. Both are valuable trees -- for timber, nuts, and wildlife -- but they are under serious threats. Butternut is in decline across most of its range due to butternut canker disease..

—- title: "How to identify walnut and butternut" slug: how-to-identify-walnut-trees hub: plants category: "Identification guide" description: "Identify black walnut and butternut by their large compound leaves, chambered pith, and distinctive nuts. Includes how to spot butternut canker before it kills your tree." date: 2026-06-10 updated: 2026-06-10 author: "Thomas A." reading_time: 8 —-

Black walnut (Juglans nigra) and butternut (Juglans cinerea) are the two native walnuts of eastern North America. Both are valuable trees — for timber, nuts, and wildlife — but they are under serious threats. Butternut is in decline across most of its range due to butternut canker disease. Understanding what separates these two species, and how to identify each with confidence, matters for landowners and naturalists.

Genus-level identification

Chambered pith: Per Penn State Extension, cut any twig lengthwise with a pocketknife. The center of the twig is divided into small, dark, chamber-like sections separated by thin cross walls. Hickory, ash, and most other hardwoods have solid, continuous pith. The chambered pith is definitive for Juglans.

Large compound leaves: Walnut leaves are alternate, pinnately compound, and large — 12–24 inches in total length with 11–23 individual leaflets. The terminal leaflet is often smaller than the adjacent lateral leaflets or absent — which is the opposite of hickory's pattern. Per NC State Extension, the large leaf size, strong spicy-nutty fragrance when crushed, and terminal leaflet reduction together separate walnut from hickory at a glance.

Leaf scar shape: The leaf scar left when a leaf drops is prominent. In both walnut species, the upper margin of the scar has a notched or pad-like cluster of lenticels that resembles a "monkey face." Per UMass Amherst Extension, this distinctive leaf scar shape is often cited as a winter identification tool.

Black walnut (Juglans nigra)

Range and size: Zones 4–9, eastern and central United States. A mature black walnut can reach 70–100 feet with a broad, open crown. Per Missouri Botanical Garden, black walnut is one of the most valuable native hardwood timber trees in North America, with figured wood commanding premium prices.

Bark: Dark gray to nearly black on mature trees, with deep, diamond-shaped to interlacing ridges. Per NC State Extension, the dark, deeply furrowed bark is distinctive — darker and more regularly ridged than butternut.

Leaves: 12–24 inches, typically 15–23 leaflets. The leaflets are narrow, lance-shaped, and finely serrated. The terminal leaflet is usually small or absent. Crushed leaflets produce a strong, characteristic walnut/spice scent.

Nuts: Round to slightly oval, 1.5–2.5 inches in diameter, in a green-yellow, unsplit husk. The husk does not split at maturity (unlike hickory). Inside is the familiar, deeply ridged black walnut shell. Per USDA NRCS, the husk contains juglone and produces a persistent dark brown or black stain on anything it contacts — hands, concrete, clothing.

Juglone toxicity: Black walnut roots and decomposing hulls release juglone, a compound toxic to many plants. Per Penn State Extension, sensitive plants include tomato, apple, blueberry, azalea, and many others. Resistant plants include most native trees, grasses, corn, beans, and squash. The toxic zone roughly extends to the drip line and a few feet beyond.

Butternut (Juglans cinerea)

Range and size: Zones 3–7, eastern North America — slightly more cold-hardy and northerly in distribution than black walnut. Smaller tree, typically 40–60 feet. Per USDA NRCS, butternut is in serious decline across much of its range due to butternut canker (Ophiognomonia clavigignenti-juglandacearum).

Bark: Gray, with broad, flat ridges and a network of interlacing fissures. Distinctly lighter gray than black walnut's nearly black bark. The ridges are smooth-topped, not as sharply cut as black walnut. Per UMass Amherst Extension, bark color alone — light gray vs. very dark — separates butternut from black walnut in the field.

Leaves: 15–30 inches, with 11–17 leaflets. The terminal leaflet is larger and well-developed in butternut — opposite of black walnut's reduced terminal leaflet. Per NC State Extension, this terminal leaflet size difference is a reliable leaf-level separator.

Nuts: Distinctly elongated-oval, not round — 1.5–2.5 inches long, roughly egg-shaped or torpedo-shaped. The husk surface is sticky with glandular hairs. Per Missouri Botanical Garden, the elongated nut shape is the single fastest field separator from black walnut when nuts are present.

Taste: Butternut kernels are notably milder and sweeter than black walnut — hence the alternative common name "white walnut."

Species comparison table

Butternut canker

Butternut canker (Ophiognomonia clavigignenti-juglandacearum) has killed an estimated 75–91% of butternuts in some parts of the range, per USDA Forest Service. It was first identified in Wisconsin in 1967 and has spread throughout the range.

Symptoms: Elongated, sunken, dark cankers on branches and the main trunk. Killed branches show discolored wood extending below the visible canker. Multiple cankers on the main stem usually indicate a fatal infection. Per Penn State Extension, there is no effective chemical treatment; removal of infected branches when less than 30–50% of the crown is affected may extend tree life.

ID confusion with black walnut: Because butternut is in severe decline, trees labeled "butternut" in nurseries or old records may have been replaced by black walnut or hybrids. Natural hybrids (Juglans × bixbyi) exist but are uncommon.

Recommended gear: Best evergreen and deciduous azaleas by zone — our buyer's guide covering picks for every budget, ranked by Extension publication consensus and personal use.

Frequently asked questions

Can I eat black walnuts? Yes. Per Penn State Extension, black walnuts are edible with a strong, distinctive flavor preferred by some for baking. Hulling is difficult — the hulls stain persistently. Hull removal is easiest when husks are still green; driving over them with a car or using a purpose-built huller are common methods.

How do I remove juglone-stained concrete? Per Penn State Extension, juglone staining on hard surfaces is very difficult to remove completely. Power washing while fresh reduces it; oxalic acid cleaners can help. Juglone breaks down in well-aerated soil over months to a few years.

Should I plant black walnut in my yard? Black walnut is a large, long-lived, wildlife-valuable tree — it produces nuts, provides habitat, and grows in zones 4–9. The juglone concern is real but manageable by maintaining a planting-free zone under the canopy. Per Penn State Extension, many common landscape plants are tolerant. The primary practical concerns are: size (70–100 ft), fruit drop mess, and the constraint on what you can grow nearby.

How do I distinguish hybrid butternuts from pure species? Per USDA Forest Service, confirmation of pure butternut vs. heartnut (Juglans ailantifolia) hybrids requires either a nuts-in-hand comparison (heartnut nuts are heart-shaped at the tip; butternut nuts are rounded at both ends with a pointed tip) or genetic testing. Many trees sold as butternut in the nursery trade are hybrids.

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Sources:

1. Penn State Extension — Black walnut
2. NC State Extension — Juglans nigra
3. NC State Extension — Juglans cinerea
4. Missouri Botanical Garden — Juglans nigra
5. USDA NRCS — Juglans nigra
6. USDA NRCS — Juglans cinerea
7. USDA Forest Service — Butternut canker
8. UMass Amherst Extension — Walnut and butternut