Degree Name

Master of Science (MS)

Semester of Degree Completion

1984

Thesis Director

Charles B. Arzeni

Abstract

The American white walnut Juglans cinerea L. is a native North American tree in the Juglandaceae, or walnut family. It prefers rich, moist, rather neutral to slightly basic lowland soils. This is an in depth study of its taxonomy, morphology, anatomy, age, size, growth habit, distribution, ecology, propagation, economic importance, medicinal uses, toxicity, folklore, diseases and pests, and chemical constituents.

J. cinerea L. is monoecious and confined in its distribution to the eastern and central parts of North America. It can be easily identified by its large, pinnately compound leaves and ashy-gray bark with broad, flat plates and deep furrows. It is a rather small to medium sized tree rarely attaining a height of more than 21.3 m or a trunk diameter of more than 91 cm. It is considered to be rather short-lived, rarely surviving more than 80 years.

The fruits, referred to commonly as nuts, but more technically dry drupes, can be used for a variety of purposes. The most important of these are as food for man and other animals, as well as a source of a yellowish-brown dye. They are very rich in oil, which probably accounts for the common name butternut. Their caloric value is 3370 calories per pound, the highest for any nut species.

The wood of this tree is very attractive and has a soft texture, light weight, and is easily workable. Because of these qualities it has been employed rather extensively in the past for interior finish and cabinet work, even though it is less durable and lower in strength than its close relative the black walnut. Despite these desirable qualities, the tree at present has little economic importance outside of local uses, such as in the New England states where maple butternut candy is made. The reason for this lack of interest is not actually known but it could be due to a variety of factors such as those mentioned above, as well as difficulty in cracking the nuts of wild trees and more importantly its susceptability to disease. The ravages of disease, combined with the great demand of this tree for cabinet work has resulted in this tree becoming very rare and scattered in native stands. A fact not known by many people is that many easily cracking, disease resistant varieties are now available through nurserymen.

Probably the most important disease of this tree, which has resulted in its widespread decline over most of its range, is a canker disease caused by the fungus Sirococcus clavigignenti-juglandacearum Nair, Kostichka and Kuntz. Another important disease is a branch canker or dieback caused by the fungus Melanconis junglandis (Ell. and Ev.) Graves.

Butternut twigs are most successfully grafted on 2-3 year old black walnut seedlings via a girdle graft or splice graft several feet from the ground just as growth begins in the spring. Grafts sometimes bear nuts after only two years from time of grafting. Trees are easily transplanted, and should be supplied with nitrogen and phosphorus fertilizer to stimulate growth and help fill out the nuts.

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