New Zealand Journal of Forestry (1978) 23(2): 224–239
©New Zealand Institute of Forestry
Black walnut - what can New Zealand learn from the United States?
Black walnut (Juglans nigra) is being considered for planting in New Zealand as a high-value timber tree. Although single specimen trees have grown well on good sites in New Zealand, very little local information is available about this species.
In the United States, black walnut occurs throughout the eastern and central regions. Natural stands are being creamed of higher grade trees, and prices for walnut logs are increasing. Despite intensive research on establishment and silviculture, many black walnut plantations fail because they are not planted on well-drained, deep, fertile soils.
Because of the absence of squirrels in New Zealand, it may be possible to establish plantations from direct sowing. Intensive plantation culture, including weed control with cultivation or herbicides, pruning to improve form and produce clear timber, interplanting with nitrogen-fixing species, and thinning before canopy closure, appear necessary to obtain rapid growth.
Seed from various United States provenances is being imported to find the best seed source for New Zealand conditions.