Juglans cinerea (Butternut)
|Also known as:||White Walnut|
|Life cycle:||perennial woody|
|Habitat:||part shade, sun; average moisture; hardwood and mixed forest, river terraces, banks, swamps|
|Bloom season:||May - June|
|Plant height:||60 to 80 feet|
|Wetland Indicator Status:||GP: none MW: FACU NCNE: FACU|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Male and female flowers are borne separately on the same branch (monoecious). Male flowers are in clusters called catkins, 2 to 5½ inches long, pendulous in flower, single in the leaf axils of 1 year old branchlets, the flowers yellowish-green with up to 15 stamens per flower. Female flowers are in a short spike at the tip of this year's new branchlets with up to 7 flowers in the spike, the flowers with a stout, green ovary covered in sticky hairs and a pair of broad, spreading, red stigma at the top.
Leaves and bark:
Leaves are alternate, usually crowded at branch tips and appearing whorled, 1 to 2 feet long, compound with 11 to 17 leaflets. Leaflets are lance-oblong, 2 to 4½ inches long, 1 to 2 inches wide, finely toothed around the edges, with an abrupt taper to a pointed tip, asymmetrical and rounded to straight across at base, and very short-stalked. The upper surface is dark green and sparsely hairy, the lower is paler in color and covered in branched hairs, especially in the vein axils, and sometimes glandular-hairy. The compound leaf stalk is green and covered in sticky hairs.
Buds are light brown and covered in short fuzz, the terminal bud cone-shaped and slightly flattened. New twigs are green to olive-brown, variously covered in a mix of glandular and non-glandular hairs, becoming smooth the second year. Leaf scars are more or less T-shaped, straight to slightly convex across the top, often with a pad of dense hairs along the upper edge. Branch pith is chambered and dark brown.
Older bark is gray to gray-brown with scattered pale lenticels (pores), smooth but developing narrow, flat ridges and broader, shallow furrows with age. Trunks can reach up to 2 feet diameter at breast height (dbh).
Fruit is oval-elliptic, 1 to 3 inches long, longer than wide, the outer husk greenish with about 8 longitudinal ridges and densely covered in short, sticky hairs. Inside is a sweet nut with a hard shell. Fruits are usually in clusters of 3 to 5 at branch tips.
Butternut was once a common forest species in the eastern half of North America, but throughout its range it's being ravaged by butternut canker, a fungal disease thought to be introduced in the 1960s though its exact origin is unknown. The disease manifests as black, open wounds in the bark of trunks, twigs and branches, and can be carried in the husks of fruit, killing any offspring of an infected mother tree. According to the DNR, it was first discovered in southeast Minnesota in the 1970s and has spread throughout the state. Listed as a Special Concern species in 1996, it was elevated to Endangered in 2013. Fortunately, a small percentage of trees appear to be immune so there is some hope of saving the species from extinction. Time will tell. Butternut closely resembles the related Black Walnut (Juglans nigra), which is distinguished by more spherical fruits that are single or in pairs and not sticky, light brown pith in the twigs, the leaflet hairs are not branched, the terminal leaflet is either missing or much smaller than the lateral leaflets, and leaf scars are notched at the tip and lack the band of velvety hairs along the top edge. Black Walnut fruits can also stain your hands black, and broken twigs and crushed leaves give off a strong, pungent odor. Butternut does neither of these.
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- Butternut tree
- Butternut tree
- upper branches
- bark of mature tree, with evident black cankers, ©Illustratedjc
- comparison of Juglans cinerea and Juglans nigra leaf scars
- comparison of Juglans cinerea and Juglans nigra pith
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