Soil Preparation/Planting Methods

Once the site is selected for planting black walnut, and the soil type is considered suitable, it is time to analyze the present site conditions.  Does the site contain a lot of weeds, grasses, or both?  Does it have shrubby growth or small trees?  Is it presently in sod?  Is it presently in row crops?  Sod would present the biggest problem since sod is detrimental to seedling growth.  Sod may be treated by spraying with a broad-spectrum herbicide.

Planting of black walnut may consist of direct seeding, or walnut seedlings.  Planting machines for seedlings may be customized for direct seedling.  A drop tube for seeds can be made so the seeds drop into the trench and then are covered with soil by the machine as it does seedlings.

Regardless, the site should be at least relatively cleared of vegetation to insure that the seedlings have little growth competition during the critical stages of development.  Seedlings are usually planted in spring, but weather and soil moisture conditions may delay planting. Direct seedling is usually accomplished in the fall.

Areas may be disked or mowed to eliminate the present vegetation or to better prepare the planting bed.  This is the time to apply pre-emergent herbicides or soil amendments if needed. 

Seedlings may also be planted by hand, using a tree planting bar or a tile spade.  Tree planting bars may be purchased from forestry supply catalogs or made by hand, using 3/4 inch pipe and a 4x8 inch piece of 1/2 inch steel.  The pieces are simply welded together to form the handle, stem, foot piece, and blade.

The tree bar is pushed into the ground at a slight angle away from you using your foot.  Push the bar away from you and then toward you, forming a slit in the ground.  The tree seedling is placed in the slit and raised slightly to straighten the roots.  Planting depth of the seedling should be at the same depth in which the seedling grew in the nursery bed.  The tree bar is then placed about 4 inches from the seedling and pushed into the ground at a slight angle toward the seedling.   The planting bar is first pulled toward you to push soil around the roots and to force out the air.  Next, the planting bar is pushed away from you to squeeze the soil against the seedling.  Remove the planting bar and "stomp" the remaining hole to fill.

Should plantings be in rows or in random?  If using a tree planting machine, your seedlings or seeds will be in rows.  Hand planting may also be done in rows, but random planting will make the stand appear natural rather than a plantation.

Should black walnut plantings be pure (monoculture) or a mixed hardwood planting?  If nut production is the goal, a pure stand of black walnut may be preferred.  If your goal is timber production, a mixed planting of other valuable hardwood species is probably desired.  If disease or insects  cause your walnut trees to die, the entire stand will be lost.  A mixed planting of other hardwoods would ensure that at least these species would be salvaged.  Companion species for black walnut include white and red oak, ash, yellow poplar, black cherry, and even white pine.

Poorer sites may include interplantings of nitrogen-fixing shrubs or plants.  This is a method of self-fertilizing the soil and providing a nursery crop for your seedlings.  Nitrogen-fixing species include black locust, European black alder, and Ceanothus, such as New Jersey Tea.  Careful considerations must be made before planting these species.  Black locust tends to form thickets and grows extremely fast.  European black alder is subject to disease that may also affect black walnut.  Plants of the genus Ceanothus may be difficult or expensive to obtain.  Autumn olive may be the best nitrogen-fixing plant but is not recommended because of its invasive habit.  It is considered an exotic invasive species in some states and is therefore illegal to sell, buy, or plant.  Unfortunately many acres of this species was planted in the 1970-1980's for wildlife and now we are paying the price for its removal or control.  It simply grows so well and spreads so fast that native vegetation cannot compete.

What about spacing for black walnut trees?  This is a subject that is debated consistently throughout the Walnut Council membership.  Some members use direct seeding methods that do not address spacing.  The closer the trees grow together, they compete with each other to form straighter trees.  However, typical spacing for walnut trees are 10x10 feet, 7x10 feet or 7x14 feet.  A 10x10 foot spacing will require 436 seedlings per acre.  Seedlings grown for nut production should be on wider spacing such as 20x40 feet.  This will only require 54 seedlings per acre and will allow for agro-forestry crops to be planted between the rows.  Intercrops may include soybeans, corn, wheat, milo, red clover, Christmas trees, pumpkins, melons, or even ginseng.