Soils Suitable for Black Walnut

The demand for hardwood seedlings is increasing because of the interest of landowners to establish new stands or plantations for economic gain for future generations, increasing wildlife habitat, stabilizing erodable soils, or for aesthetic purposes.  Whatever the reason, hardwood seedling demand often exceeds supply.

Landowners who are more interested with planting hardwoods for a future income, often select black walnut, one of our highest valued hardwoods.  Before planting and cultural care are even considered, site selection is of utmost importance.  Proper site and soil selection increases the probability of a successful planting and will reduce the length of time between planting and harvest.  Careful consideration should be given to soil drainage, soil type, soil depth, soil texture, and the slope of the land.

Soils have specific physical and chemical characteristics which will affect the growth of black walnut.  Soil types are defined on a local soil survey map, obtained at your local County Soil and Water Conservation District office.  Each soil is given a name and a number in the soil survey description.

Landowners who are interested in growing black walnut may wish to contact a forester for assistance.  In Illinois, soils considered suitable for growing black walnut trees have been placed in three categories.  They are: (1) suitable, (2) questionable, and (3) unsuitable.  Questionable soils may require an on-site evaluation by a forester or soil scientist.

When the landowner's proposed planting site has been identified on the soil survey map, a soil series number is given, which identifies the soil series name.  A letter may follow the number.  This letter refers to the slope.  Slope classes are as follows:

A third number, if given, refers to the erodability of the soil.

Suited soils for growing black walnut trees include a well drained to moderately well drained soil.  It should have a depth of 40 inches.  This refers to the thickness of the soil that contains the root zone.  In other words, it is the soil material in which roots can penetrate easily to obtain water and nutrients.  This is called the A and B horizons of the soil.  Horizons are identified by soil color and textures which change with the depth of the profile.  The C horizon is unsuitable for root growth because it may feature impenetrable claypans, frazipans, or even bedrock.

Suitable soil textures include loam, silt, silt loam, clay loam, silty clay loam, sandy clay loam, or fine sandy loam.  You may determine texture yourself, by simply feeling the soil in your hand.  A "loam" is a combination of silt, clay, and sand.  Silty soils have the texture of flour.  If you wet your hand, or if the soil is wet, squeeze the soil between your thumb and forefinger.  If it forms a continuous ribbon, it has a high clay content.  Sandy soils will have a gritty, sandy feel when rolled between your fingers.  A silty clay loam has little grit and feels soft, but "ribbons" when squeezed.  Different combinations form the various textures described.  Soil pH refers to the acidity or alkalinity of the soil.  The number "7" is considered neutral.  Numbers less than 7 are acidic in nature while numbers greater than 7 are considered alkaline.  Suitable soil pH for black walnut is 4.5 to 8.4.

Suitable slopes for black walnut growth is 0-15%, or letters A-D on the soil series.  If slope is the only limited feature, soils in coves or on north and east facing lower slopes are considered suitable.  Soils on south and west facing upper slopes are considered unsuitable.

The following listing contains soils listed as suitable for growing black walnut in Illinois.  For simplicity, soil erodability classes are not given.  These soils exhibit the descriptions previously given for "suitable" soils for growing black walnut trees.  Landowners in states other than Illinois may match the suitability descriptions to their local soil survey maps.