Regeneration of Black Walnut to Sustain Production on Forested, Deep-Alluvial Soils Along a Creek
Our existing component of high-valued walnut is not naturally sustainable in mixed-timber stand along our creeks because walnut seedlings do not get sufficient direct sunlight. As such sites are logged or high-graded for walnut, low-valued species fill in the gaps. The objective is to compare two levels of site preparation to regenerate walnut on a creek bottom site dominated by stagnant, low valued brush and timber in order to sustain a healthy, high-valued walnut forest.
Seeding: Supplemental direct seeding of walnut was done in October, 2007. Four transects were flagged, two nuts were planted 2 inches deep, and covered by a 12×12 inch piece of ½ inch gauge wirecloth anchored with u-shaped, five-inch landscape pins. The screens were put in place to protect the nuts from squirrels during the winter months to avoid predation.
Additional Girdling: Some culled trees were not completely killed by the initial girdling and herbicide treatment. Most escapes were initially done in March or April of the previous year during heavy sap flow. During heavy sap flow, some of the herbicide is flushed out of the kerf by the flowing sap. This reduces herbicidal effectiveness resulting in some basal sprouting of the girdled tree. These escapes had to be cut off and treated.
Additional Seed Collection: Approximately 500 nuts were collected from walnut trees on site during the fall of 2008 and placed in a vernalization pit so they will germinate when direct seeded during the spring of 2009.
We learned that these 5-inch anchors failed to hold the wirecloth screen close to the soil surface. During the winter months, frost heaved the anchors up about 2 inches which allowed the squirrels to lift one side of the screen high enough to dig out the two walnuts.
It still appears that more volunteer walnut seedlings are emerging in the treatment blocks that were physically cleared of all culled trees versus where culls were merely killed by girdling and left as standing dead trees.
Suppressed pole-sized walnut, oak, and cherry indeed produced numerous epicormic sprouts in response to being released from taller, dominant overstory of sycamore, etc. These will have to be coppiced at ground level rather than let them continue to form low-grade butt log with side limbs and become a dominant “wolf tree” among the new volunteer seedlings.
There was no apparent herbicidal damage to a volunteer walnut seedling that emerged within 1.5 feet of a 26” stump that was treated with herbicide.
WORK PLAN FOR 2009
Coppice the suppressed walnut, oak, and cherry that produced numerous lateral sprouts. The root collar will produce 2-10 sprouts. Eventually, the strongest sprout will be saved while all others will be trimmed so that the tree will have only a single stem. These coppiced resprouts will now be competing with similar sized volunteer walnut.
Direct seeding of vernalized nuts in areas that appear to be void of new volunteer walnut seedlings so we end up with a relatively uniform stand of 40-100 seedlings per acre. Ultimately, the juvenile stand will be thinned to about 35 per acre.
Presentation: An update of the project was presented to 205 attending the National Walnut Council Conference as hosted by the MO Chapter of the Walnut Council here in Columbia, MO on August 3-6. Attending members were provided a guided tour of the site, treatments, and reforestation results to date.
This SARE Project will be reviewed as part of a presentation to the Callaway County’s Annual SWCD Meeting with an anticipated attendance of 150 on March 19.
A field tour is being planned for later this spring for neighboring farmers and other landowners, MU Extension, NRCS, Farm Bureau, and the Walnut Council.