Butternut, or white walnut, is a medium-sized tree with a short trunk dividing into several ascending limbs that form an irregular or round-topped crown.
Leaves are alternate, feather-compound, 10–20 inches long, with sticky hairs on the leaf stalk. Leaflets 11–19, 2–4 times longer than broad to lance-shaped, 2–5 inches long, 1½–2 inches wide; margin with small teeth, tip pointed; upper surface yellow-green with fine hairs; lower surface paler, with sticky hairs when young; leaves turn yellow in autumn.
Bark is gray to light brown, sometimes whitish, grooves deep, ridges broad, smooth, flat, short, roughly forming diamond-shaped patterns, chocolate-colored when cut.
Twigs are stout, brown to grayish-brown, hairy; pores white, conspicuous; end bud large, ½–¾ inch long, hairy; pith of twig dark brown, separating into chambers when cut lengthwise.
Flowers April–May. Male flowers in catkins, female flowers in a short spike on the same tree.
Fruits September–October, in clusters of 1–5, drooping, odor strong, 1½–3 inches long, rather cynindrical (broadest in the middle and narrowing at two equal ends), with 2–4 lengthwise ridges, light brown, sticky with rust-brown hairs, not splitting open to expose the nut; nut conspicuously 4-ribbed, sometimes with 4 fainter ribs, light brown, broadest in the middle and narrowing at both ends, 1–2½ inches long; seed sweet, oily, edible.
Key identifiers:
- Leaves long, alternate, feather-compound, with sticky hairs on the leaf stalk
- Leaflets 11–19, toothed, upper surface with fine hairs
- Fruits distinctive, sticky with rust-brown hairs, with strong odor, not splitting open to expose the fruit
- Bark gray, tan, or whitish, deeply grooved with rather diamond-shaped patterns, ridges broad
- Twigs stout, with chambered pith
Similar species:
- Black walnut (Juglans nigra) is closely related and much more common in Missouri. Its fruits and the nut within are rather spherical; the leaf scars have the upper edge notched (not straight) and are not bordered by a well-defined velvety ridge (as butternut's leaf scars are).
- The mild-tasting English (or Persian) walnut is the species J. regia. It is native to Eurasia and when cultivated in Missouri does not escape. The state of California grows nearly all of the US commercial supply of English walnuts.
- Walnuts are in the same family as hickories and pecans.
Height: to 60 feet.
Scattered and declining in the eastern two-thirds of Missouri, mostly in low and moist soils. Generally absent from western and northwestern prairie sections of the state.
Habitat and Conservation
Butternut occurs in moist woods at the bases of slopes and bluffs, and along streams, where soil is rich and moist but well drained. Butternut trees cannot survive being shaded and do not compete well with other trees. Several varieties of butternut have been developed for cultivation; special traits of these include thinner shells that are more easily cracked.
Status
Unfortunately, butternut is in serious decline throughout its range because of butternut canker, a usually fatal fungal disease that girdles the branches and stems. This species is on the road to extinction unless a cure is found. One route to its salvation might be through cross-breeding butternuts with a canker-resistant species, then breeding resistant hybrid offspring with butternuts to regain more traits of the butternut while retaining the resistance to the canker. Overharvesting butternuts commercially for lumber has contributed to this tree's decline.
Human Connections
Butternut wood is not as hard as black walnut, but it is nevertheless valuable for furniture and woodcarving.
Native Americans and white settlers harvested the buttery fat left from boiling the nuts, giving the plant its name.
People in New England make maple-butternut candy.
In the 1800s, people often dyed their homespun cloth a yellowish-brown using butternut bark and fruit hulls, and people who wore these fabrics were called "butternuts." Confederate soldiers were called butternuts apparently because when their gray uniforms faded, the color resembled this homemade cloth.
Butternut extracts have been used medicinally in the past.
Ecosystem Connections
Many animals relish the sweet, oil-rich nuts, notably mice and squirrels.
Many insects eat the wood, leaves, fruits, and other parts of the tree, including weevils, borers, lace bugs, and bark beetles.
The hickory horned devil, the large and spectacular caterpillar of the royal walnut moth, eats walnut and hickory leaves.
Like black walnut, butternut produces juglones, chemicals that inhibit growth of many plants nearby the tree.
