Butternut, Juglans cinera, is a native tree to much of the eastern United States, ranging from New Brunswick and Maine south to northern Georgia, and all the way west to Missouri. Not a particularly striking tree in the landscape, as the light grayish bark stands out amongst the browns and darker shades in the woods better than most suburban settings. The bark does develop deep fissures when older, with the darker undertones providing some relief to the light.
The tree is normally found in the forest mixing with white ash, sugar maple, red oak, and elm, the classic mix in the Champlain Valley and elsewhere. It prefers well drained, deep soils, with a limestone base. Light hungry, the tree is often dominant or co-dominant in the forest, and is fast growing, with a life span of a short 75 years or so.
A good, tall butternut might reach 30-40 feet, with a spread about 20’ grown all on its own. Julia Ellen Rogers, in a great old book called ‘Among Green Trees’ (more on her later) notes a tendency of the lower buds on a twig or branch to develop, giving the tree therefore a broad spreading form. Fergus notes the tree can be compared in shape to a very large apple tree, with a short trunk branching low.
The tree is called a butternut, obviously, for the plenitude of nuts it produces. The nut is said to be oily, sweet and buttery, and able to quickly go rancid. Charles Fergus in ‘Trees of New England‘ claims ‘like a mild black walnut with a hint of banana’. They bear nuts young, at 20 years of age or so, with best production at 30-60 years. 3-5 nuts hang in clusters, and ripen to a dark tan sticky mess, staining your hands well beyond the ability of soap to quickly wash it away, time doing a better job of it. The plant produces male and female flowers on the same stem, with the female flowers on the new growth, males emerging lower on the stems on older growth from last year.
The leaves are alternate and compound, meaning many leaflets per stem. It tends to have longer stems and less leaflets than a black walnut, with which it is easily confused (at least by me.) The leaves are a yellowish green, with a yellowish brown fall color, and tend to get tattered and dingy throughout the growing season. The tree is one of the last to break bud in the spring, and one of the first to drop in the fall. Rogers claims ‘Until the spraying of shade trees becomes a common practice, let us set them, not in our front yards, but back a little, where the perspective is just right to emphasize their fine stature and luxuriant foliage, while obscuring unpleasant details.’
Butternut-Uses and Ecological Niche
Native Americans used the nuts as an excellent food source, both cooked and raw, even grinding them into rudimentary meal type flour. The Iroquois extracted oil from the seeds, and used it for hair. Some of you may have heard confederate soldiers being called ‘Butternuts’, the name deriving from the dye used in their uniforms. The tan color is easily extracted from most parts of the plant, including the leaves, fruit, and twigs.
The branches and trunk has only a small strip of sapwood, usually very light in color. The majority of the wood is heart wood, a rich brown color with intricate grain. The other common name, White Walnut, derives from this lighter colored wood than Black Walnut. Rogers states (a little snarkily for 1902) ‘Compared with it (butternut), black walnut in a house always looks somber and severe’.
Not only lighter in color, the lumber is also lighter in weight, and was therefore used extensively in high end coaches and carriages, as well as private railroad cars. It is quite stable, very rarely cracking or checking, and prized by carvers and wood turners.
Butternut fruits are also high in anti-oxidants, as well as anti-fungal properties seen in the bark, pointing to potential pharmacological uses.
Butternut is an important tree ecologically in the region. Obviously, the large nuts are useful to squirrels and other wildlife. Bird species favor the tree to, with Fergus noting yellow bellied sapsucker, bluebirds, and starlings all frequenting his trees. Doug Tallamy (in a book you must read, Bringing Nature Home) notes the foliage hosts over 100 species of Lepidoptera, the butterflies and moths family. Several species have specialized in walnuts, including the gregarious walnut caterpillar, Angus’s Datana, the gray edged bomolocha, and the Butternut wooly worm.
Butternut canker, Sirococcus clavigignenti-juglandacearum, is a fungus infecting nearly all butternuts across the United States. Especially virulent, the spores enter the tree through many pathways, including leaf scars and lenticels on small twigs, and on older stems through wounds and cracks. Often the first infection appears high in the tree on smaller growth, and moves downward through the canopy.
A canker is merely a fancy name for an area of dead tissue on a stem. Butternut canker causes the wood to turn dark and mushy beneath the bark, where it destroys the cambial layer. The tree, given enough infection points, eventually starves to death, its vital pathways of nutrients and water cut off under the bark. To add insult to injury, the fungus can live and reproduce in a dead tree for up to 20 months.
Chestnut Blight, another fungus, has effectively killed all large chestnuts across the US. Chestnut is still around, however, based on its ability to sucker from the base, as the blight only infects older trees. Dutch Elm disease is similar, only infecting trees at about 30 years old, well after the tree’s reproductive years start. Butternut canker, though, is a complete killer, infecting even young trees before reproductive age, and it is conceivable that butternut could be completely eliminated as a species.
First identified in Wisconsin in 1967, research now points to it being seen up to 70 years ago on the southern end of its range. Once seen in 1967, it promptly killed 58% of the butternut in Wisconsin and 91% in Michigan in 15 short years. There is no known control.
The butternut orchard on South Street is part of an interdepartmental ‘rescue’ effort of Butternut trees in Vermont. The main drivers are the USDA Forest Service, and the State of Vermont Department of Forest, Parks and Recreation. Similar programs are underway in Minnesota, Wisconsin, Illinois, New York, Indiana, and New Hampshire. The basics are easy to understand, the actual effort herculean.
Healthy butternut trees are located in the wild. Because the tree is often found in groves (squirrels being essentially lazy, hiding and forgetting nuts in a relatively close range), any healthy butternut found in proximity to other infected trees is thought to have some degree of resistance to the canker. To determine disease resistance, strict protocols as to the health of the tree are followed: for example, in New Hampshire 3000 possible trees were evaluated at 300 sites, and only 8 trees selected for the possible resistance.
Scions of healthy wood are collected from the crown of the tree, and sent out west to a USDA greenhouse for grafting. The success rate of grafting hardwoods is only about 50%. The surviving trees are grown in the greenhouse for a while, and then planted out in seed orchards in various locales. The mixed population of potential resistant trees is allowed to cross pollinate with each other, and then this seed is collected, now thought to be disease resistant. The fancy name for this is Intraspecific Breeding.
Within Vermont, potential trees to breed have been found in Williston, Derby, Charlotte, Shelburne, St. Albans, Shaftsbury, Castleton, Jericho, Berlin, and other places. The first seed orchard is growing on Forest Service land in Brandon, and Middlebury College was approached to host a second site, following the ancient stricture of not putting all of ones eggs in a single basket. We selected a one acre site on an awkward corner of a corn field, across from Eastview at Middlebury, and with the help of a grant from the State of Vermont constructed an 8’ high fence to keep the deer from the young trees. We planted 38 trees on one of the hottest days of the year, and have mulched and watered. Now, we wait. These trees will cross breed with each other, and the seeds collected. Hopefully the progeny will be disease resistant, and butternut can start to be reintroduced.