Maine Tree Species  Fact Sheet

Common Name: Butternut (White Walnut, Oilnut)
Botanical Name: Juglans cinerea
Tree Type: Deciduous

Physical Description:

Growth Habit: Butternut is a close relative of the black walnut.  It is a small to medium-sized, short-lived tree.  It grows best on streambanks and on well-drained soils; it is seldom found on dry, compact or infertile soils.  On young trees, the bark is smooth and the branches are light gray.  On older trunks, the bark is deeply divided into long, broad, flat-topped whitish ridges.  The inner bark becomes yellow with exposure to air.  The twigs are stout, brittle, and greenish-gray in color, often hairy and easily identified by the dark-brown furry growth, or “mustache” found just above most leaf scars.  The leaves are alternate, pinnately compound, 10-20 inches long with 11 to 19 leaflets (each leaflet 2-5 inches long). They are dark green and finely pubescent above and glandular beneath.  The margins are serrate and the leaf stalk is hairy where it joins the stem.

Height:  The butternut reaches a height of 30-40 feet with a spread of 30-50 feet and a trunk diameter of 1-2 feet.  This species is hardy in Zones 3 to 7.

Shape:  The butternut has stout spreading limbs, which extend horizontally from the trunk to form a low, broad, rounded head.   The tree is usually round-topped with a short, forked or crooked trunk and somewhat open wide-spreading crown or large horizontal and stout stiff branches.

Fruit/Seed Description/Dispersal Methods:

The butternut flowers from April to June, depending on its location.  The species is monoecious.  Male and female flowers are both small and do not have petals.  They are clustered in catkins.  The male catkins are greenish, up to 4 inches long and hanging.  The female catkins are short and borne separately.

The fruit is an oblong-ovoid pointed nut, 1 ½ to 2 inches long.  They mature in September and October.  The nuts occur singly or in clusters of 2 to 5 and are enclosed in a pointy, sticky green husk.  They usually remain on the tree until after leaf fall.  The kernel of the nut is sweet, oily and edible.

Range within Maine:

The butternut occurs statewide on rich moist soil and on rocky hills, especially along fences.

Distinguishing Features:

Butternut has an elongated, rough, sweet, edible oily nut, which is enclosed in a pointed, sticky green husk in clusters of up to five.  The twigs have a dark-brown, furry “mustache” just above most leaf scars.  The pith of Butternut is chambered and dark brown as opposed to the light brown-chambered pith of the black walnut.

Interesting Features:

The wood is coarse-grained, light soft and weak.  It is occasionally used for making cabinets, toys and novelties.  Butternut is more valued for its nuts than its lumber.  The nuts are especially popular in New England for making maple-butternut candy.

Relationship to Wildlife:

The common grackle has been reported to destroy immature fruit and may be considered a pest when populations are high. 

Landscape Use:

The butternut prefers the moist, deep, rich soils of bottomlands.

Common Problems or Pests of the Tree in Maine:

Some insects commonly found on butternut include wood borers, defoliators, nut weevils, lacebugs, and bark beetles.  The most serious insect pest is the butternut curculio, which injures young stems and fruit.

The most serious disease of the butternut is butternut decline or butternut canker, which is caused by a fungus.  Symptoms of the disease include dying branches and stems.  Bunch disease also attacks butternut.

References:

Forest Trees of Maine, Twelfth Edition.  Maine Forest Service/Department of Conservation. 1995.

Know Your Trees. Cope, J.A. and Fred E. Winch, Jr. Cornell Cooperative Extension. 1992.

Manual of Woody Landscape Plants, 5^th Edition.  Dirr, Michael A.  Publishing L.L.C. 1998.

United States Dept. of Agriculture: Silvics of North America:

http://www.na.fs.fed.us/spfo/pubs/silvics_manual/volume_2/juglans/cinerea.htm

Smithsonian Handbook: Trees.  Coombs, Allen J. Dorling Kindersly. 2002.

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