Click on the forest type you want to view.
|Aspen||Bur Oak||Northern White-Cedar|
|Balsam Fir||Eastern White Pine||Red (Norway) Pine|
|Birch||Hemlock-Yellow Birch||Silver Maple-American Elm|
|Black Ash-American Elm-Red Maple||Jack Pine||Tamarack|
|Black Spruce||Maple-Beech-Yellow Birch||White Oak-Black Oak-Northern Red Oak|
|>Black Walnut||Northern Pin Oak|
| Description | Products and Uses | Site Conditions |
| Regeneration | Immediate Treatments | Pests and Diseases |
Black walnut (Figure 6-6) generally is found scattered among other tree species. Pure stands are not common, but do occur. Common associates include yellow-poplar, white ash, black cherry, basswood, beech, sugar maple, oaks, and hickories. Its leaves and roots actively secrete material toxic to some trees, shrubs, and herbaceous plants.
Wood products from black walnut include sawlogs, veneer logs, gun stocks, and smaller novelty pieces. Nuts are excellent for human consumption. Frequent nut crops make it an excellent tree for wildlife, especially squirrels. Nut shells are used as an abrasive in grinding and polishing.
Walnut grows best on lower north- and east-facing slopes, stream terraces, and floodplains. It is common on limestone soils and grows well on deep loams, loess soils, and alluvial deposits that are fertile and moist, but well-drained. Poor sites for walnut include steep south- and west-facing slopes, narrow ridgetops, and poorly drained sites. Soils with acid clayey subsoils, coarse sand or gravel layers, or bedrock within 2.5 feet of the surface are not suitable for walnut. Site index curves for black walnut plantations are in Appendix B-4.
The rotation length for black walnut is 50 to 80 years. It naturally regenerates from seed and stump sprouts if trees are less than 20 to 30 years old. Since black walnut trees normally are a minor component of a woodland, natural regeneration is unreliable and planting seedlings is recommended. Black walnut is intolerant of shade. To prepare a woodland site for planting, cut or kill with herbicides all woody vegetation larger than 0.5-inches in diameter. On grassy and weedy sites apply herbicides in the year before planting to kill existing vegetation in planting strips or blocks. Plant seedlings at a spacing of 10 by 10 feet for timber production and 15 by 15 feet for a combination of timber and nuts. In field plantings for timber, planting a conifer (such as white or red pine) in every third row may increase the survival rate, growth rate, and improve the stem form of walnut trees. Plant seedlings in the spring as soon after the ground thaws as possible. Use seedlings at least 1/4-inch in diameter, measured 1-inch above the root collar.
Seeds are easier and less expensive to plant than seedlings, but must be protected from squirrels and other rodents. Mechanical barriers (such as hardware cloth and tin cans) are most reliable, but they are expensive and time consuming to install. Sow seeds in either fall or spring. Husks do not need to be removed for fall planting. Spring planting eliminates overwinter feeding by rodents, but requires that the seed be stratified before planting to break dormancy. (Stratification involves subjecting seed to cold temperatures and regulating moisture usually for a couple of months but variable by species.)
Control weeds for at least three years after planting to maximize the sunlight, moisture, and minerals available to walnut seedlings and to reduce plant cover that encourages rodents. Control weeds by mowing or cultivation in open field plantings or by herbicides. In most situations herbicides are more cost effective and reliable than mowing or cultivation.
Corrective pruning can improve seedling form if tip dieback or stem forking has occurred. Do not prune too heavily; young stems have a strong natural tendency to grow upright. Clear-stem pruning is recommended to help produce knot-free wood. Fertilization generally is not needed on a good black walnut site unless a specific nutrient is deficient. Foliage analysis will reveal any nutrient deficiencies. Weeds are the usual benefactors of fertilizers.
Thin the stand lightly and frequently, perhaps every 10 years, to maintain rapid, uniform growth. If you planted conifers along with the walnuts, remove the conifers when they compete for crown space. When thinning, provide at least 5 feet of space around three-quarters of the crowns of crop trees. Select crop trees early by choosing those with straight stems, one dominant leader, well-formed crowns, and no apparent signs of disease or injury. Kill competing trees by felling or girdling and treating them with an herbicide.
The major pests of black walnut are walnut caterpillars and bud borers. Pesticides usually are not economical. The major diseases that infect black walnut are anthracnose and fusarium canker. Fungicides may be necessary to control anthracnose for the purpose of improving nut production, and insecticides may be necessary to control caterpillars. Anthracnose can be managed by controlling weeds that weaken the trees. Fusarium canker can be controlled by restricting pruning to late winter. Fire is highly damaging to black walnut.
Incorrect pruning can lead to serious problems, including fusarium canker, bark necrosis, and sun-scald.