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Establishing and Maintaining a Black Walnut Plantation

Photo from Div. Forestry, WRAP doc., TVA 1978

You have expressed a desire to grow black walnut (Juglans nigra) The wood supply is limited, there are changing market values as well as styles and uses. The locations of manufacturers makes an investment in walnuts a challenging but promising activity. Staff seek to maximize the profits from the sale jointly over time of nut-meats, shells, and wood, both delivered and processed on site.

Currently walnut is bringing from XXX to XXX per 1000 board feet. Walnut nut meats are bringing XXX per pound.

Site selection, site preparation, sowing of seed, plantation type and spacing, and maintenance all singly and together determine whether any landowner will make a profitable return. Group efforts are strongly encouraged to achieve adequate and stable supplies for markets which need to be built.

This is one of the few, if not the only, forest tree species whose value warrants the application of intensive cultural methods. Many management decisions are involved in this type of enterprise. Site selection and preparation, planting, plantation type, spacing and maintenance are all factors influencing the success or failure of a black walnut plantation. Volumes could, and have been written, on black walnut culture. Here we start a conversation about optimum conditions and preferred techniques. Over time, more detail will be added here but check with the staff about latest findings.

Site Selection

Selection of the site, and associated soils, is the first, and perhaps most critical decision you must make. The best sites are bottomlands, or coves and their adjacent lower slopes with a North or East exposure. For optimum growth, walnuts require deep, rich, moist soils of "alluvial origin" (meaning water deposited). The soils should have 8 to 10 inches of topsoil and 10 to 16 inches of friable, mellow, well-drained underlying soil. Select the best soils you can find. Walnut does best on loose, easily-worked soils that are well drained, but have an adequate supply of water. Frost pockets, and lands subject to more than occasional flooding should be avoided. Worn-out fields, swampy areas, and dry hillsides or ridges are poor choices as sites for black walnut. Good corn land is usually good walnut land, but check the subsoil. It should be friable, and not waxy when wet. A near neutral, or only slightly acid condition should prevail (check this with a pH meter go for land with 5.8 to 6.1.

Walnut growing is well suited to pasture land use because the trees provide shade for livestock, goats and cattle, and pasture grasses thrive under them.

Spacing

Black walnut should be planted about feet apart. Closer planting requires intermediate thinning, but by the time walnut reaches the point where thinning is required, you have too much invested in time and money, and the trees have too much potential value for you to risk destroying the surplus stems. Wide spacing eliminates the need for thinning, but substitutes the need for more intensive pruning to insure production of straight, clean stems for maximum dollar return.

Site Preparation

Because of the extreme intolerance of walnut to shade, all competing vegetation should be removed from the site by mowing, chemical controls, or both. Each planting site should be scalped (vegetation removed to the bare ground) for a distance of 18 inches around each seedling, or seed spot, and the scalped area treated with Simazine (4 pounds per acre) to retard re-vegetation. Herbicide treatment in the second year is likely to be needed.

Plantation Establishment

Whether to plant pure or mixed stands is a difficult decision. Black locust can be interplanted. Walnuts are toxic to some other hardwood trees (and to pines) and to many garden crops.

You may establish your plantation by either of two methods. You may plant one-year-old nursery grown seedlings, or you may direct seed in the early spring using stratified seed. In either case, the nuts should be collected in the autumn and come from trees in the same general region (within less than 100 miles and within 1000 feet of the same elevation) and from trees selected for their desirable characteristics.

In planting seedlings, dig a hole a foot in diameter and a foot deep at each planting site. Protect the long tap root. Place the seedlings in the hole with roots extended. Long roots may be pruned to fit, but use caution. Fill the hole loosely with soil and firm slightly to remove large air pockets. Water if necessary.

Spacing needs to be based on objectives. Tight spacing will tend to produce tall straight boles and reduce epicormic branching. This suggests 10 feet. If epicormic branching is desired (wood patterns etc.) and nut production essential as an annual crop prior to wood harvest, then wider planting is needed. A temporary suggested spacing is thus 25 feet. This optimization is being studied for the current markets.

A unique design is recommended for a grove of walnut trees for producing wood, nut-products, livestock forage, and habitat for certain wild animals. It was developed by Kevin Killeen for the Nettletons' area, Covington, Virginia. Distances can be adjusted based on latest computer models. The final hexagonal configuration maximizes sunlight collection. Intermediate stems removed are used in high-value on-site products (carving woods, picture frames, furniture blanks, etc.). A planting procedure is suggested.

For direct seeding, plant nuts that have been stratified over winter in moist sand, or peat, at temperatures of from 35 degree F to 50 degrees Fahrenheit. Optimum temperature is 37 degrees Fahrenheit. The nuts are planted, three to a spot, about two inches deep and firmed in with the foot. Germination can be expected from 15 to 45 days after planting. Nuts sown in the fall (not recommended) take 100 to 300 days to germinate (if not destroyed by rodents).

Replanting is essential in the second year if adequate germination (<h;70%) or growth has not been achieved.

In areas with high rodent populations, may be necessary to plant the nuts in cans to lessen losses to these animals. This is accomplished by cutting one end out of a can and cutting an "X" in the other. The nut is placed in the closed end of the can, the can filled with dirt and planted, X end up, the recommended 2 inch depth.

Maintenance

It is absolutely essential that competing vegetation be kept under control, at least until the seedlings attain sufficient height growth to prevent their being overtopped. Weed control may be obtained by either mowing, or by chemical control, but in either case caution must be used to prevent damage to the seedlings, either by mowing equipment, or by the drift of carelessly used herbicides. Clean cultivation is not recommended because of increased likelihood of erosion and the probability of damaging the shallow feeding roots of the seedlings.

Frost, insect, or disease damage can be serious and prompt treatment is needed. Sterilize and treat frost cracks to prevent further damage. The" walnut datana" caterpillar causes defoliation. Destroy each colony. Only severe attacks require insecticide applications. Fungi and mildew often hit young plants but there are so many options that an expert must be contacted.

Interplanting

During the early years of the plantation, a great deal of useable growing space goes to waste between the widely-spaced seedlings. This may be utilized in several ways. Commercial species of trees compatible with walnut may be planted in double rows between the seedlings. Yellow-poplar may be used as "nurse" trees to force the walnut into more height growth. Black locust also benefits the seedlings through fixing nitrogen and delivering it to the walnut roots. In any case, the inter-planted species should be removed when they reach pulpwood size or they will reduce walnut production.

Unless the hexagonal patterns are used as suggested above, follow stocking guides for other forests - when 100 % dense, remove 60%.

This allows the stand to reach 100 % stocking at harvest age.

A cover crop, such as soybeans or lespedeza is beneficial in reducing weed competition, improving fertility, improving wildlife habitat and at times, providing an interim income.

Pruning

Pruning should be initiated as early as the first growing season to eliminate obvious double leaders. This type of pruning should be continued each year until the saplings reach a height of 10 feet, then pruning should be extended to remove all branches from the lower 5 feet of the trunk. Branches should be removed flush with the trunk before they reach an inch in diameter. As the tree grows, this practice is continued until a minimum of 17 feet of clear trunk is reached. Lower branches are removed to reduce nut harvesting difficulty.

Fertilization

Although the quantitative effects of fertilization are not accurately known,it is known that black walnut responds favorably to this practice. Consider applying 300 pounds of 10-10-10 per acre every 2 years. Whether costs or fertilization are offset by the increased growth and gains in tree and nut production over time is yet to be determined.

This brief unit only highlights the approved techniques of establishing a black walnut plantation under optimum conditions. The assistance of the TVA Department of Forestry, the WRAP System, about 1973, is appreciated.

contact Northern Nut Growers Association, Inc. for two-volume Guide (September, 2004)

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Last revision July 13, 2001.