Juglans cinerea

Juglans cinerea subsp. var.	Butternut, Butternut Walnut, White Walnut
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	Juglandaceae > Juglans cinerea var. ,

Juglans cinerea, commonly known as Butternut or White Walnut, is a species of walnut native to the eastern United States and southeast Canada, from southern Quebec west to Minnesota, south to northern Alabama and southwest to northern Arkansas. It is absent from most of the Southern United States.

It is a deciduous tree growing to 20 m tall, rarely 30 m, and 40–80 cm stem diameter, with light gray bark. The leaves are pinnate, 40–70 cm long, with 11-17 leaflets, each leaflet 5–10 cm long and 3–5 cm broad. The whole leaf is downy-pubescent, and a somewhat brighter, yellower green than many other tree leaves. The flowers are inconspicuous yellow-green catkins produced in spring at the same time as the new leaves appear. The fruit is a nut, produced in bunches of 2-6 together; the nut is oblong-ovoid, 3–6 cm long and 2–4 cm broad, surrounded by a green husk before maturity in mid autumn. Butternut grows quickly, but is rather short-lived for a tree, rarely living longer than 75 years.

Key characteristics:

• Alternate, compound leaves
• Odd number of leaflets- has a terminal leaflet
• Fruit normally grows in groups of 2-3 and is lemon-shaped

Butternut is found most frequently in coves, on stream benches and terraces, on slopes, in the talus of rock ledges, and on other sites with good drainage. It is found up to an elevation of 1500 m (4,900 ft) in the Virginias- much higher altitudes than black walnut.

Butternut flowers from April to June, depending upon location. The species is monoecious. Male flowers are slender catkins that develop from auxiliary buds and female flowers are short terminal spikes home on current year's shoots. Flowers of both sexes do not usually mature simultaneously on any individual tree.

Commercial seed-bearing age begins at about 20 years and is optimum from age 30 to 60 years. Good crops can be expected every 2 to 3 years, with light crops during intervening years.

Standard Cyclopedia of Horticulture

Juglans cinerea, linn. butternut. white Walnut. Large tree, occasionally to 100 ft., with gray bark: young branchlets villous and glandular: lfts. 11-19, oblong-lanceolate, acuminate, appressed- serrate, usually pubescent on both sides, more densely below 3-5 in. long: fr. in short racemes, 2-5, oblong, pointed, 3-5 in. long; nut oblong, with 4 more and 4 less prominent irregular ribs and many broken sharp ridges between. New Bruns, to Ga., west to Dak. and Ark. The above text is from the Standard Cyclopedia of Horticulture. It may be out of date, but still contains valuable and interesting information which can be incorporated into the remainder of the article. Click on "Collapse" in the header to hide this text.

Cultivation

Butternut grows best on streambank sites and on well-drained soils. It is seldom found on dry, compact, or infertile soils. It grows better than black walnut, however, on dry, rocky soils, especially those of limestone origin.

Pests and diseases

Butternuts killed by butternut canker

The most serious disease of Juglans cinerea is butternut decline or butternut canker. In the past the causal organism of this disease was thought to be a fungus, Melanconis juglandis. Now this fungus has been associated with secondary infections and the primary causal organism of the disease has been identified as another species of fungus, Sirococcus clavigignenti-juglandacearum. The fungus is spread by a wide-ranging vector, so isolation of a tree offers no protection. Symptoms of the disease include dying branches and stems. Initially, cankers develop on branches in the lower crown. Spores developing on these dying branches are spread by rainwater to tree stems. Stem cankers develop 1–3 years after branches die. Tree tops killed by stem-girdling cankers do not resprout. Diseased trees usually die within several years. Completely free-standing trees seem better able to withstand the fungus than those growing in dense stands or forest. In some areas, 90% of the butternut trees have been killed. The disease is reported to have eliminated butternut from North and South Carolina. The disease is also reported to be spreading rapidly in Wisconsin. By contrast, black walnut seems to be resistant to the disease.

Bunch disease also attacks butternut. Currently, the causal agent is thought to be a mycoplasma-like organism. Symptoms include a yellow witches' broom resulting from sprouting and growth of auxiliary buds that would normally remain dormant. Infected branches fail to become dormant in the fall and are killed by frost; highly susceptible trees may eventually be killed. Butternut seems to be more susceptible to this disease than black walnut.

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

Butternut is very susceptible to fire damage, and although the species is generally wind firm, it is subject to frequent storm damage.

Gallery

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References

• Standard Cyclopedia of Horticulture, by L. H. Bailey, MacMillan Co., 1963

External links

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