BLACK-WALNUT PROVENANCE PERFORMANCE IN 7 22-YEAR-OLD PLANTATIONS

In 1967, black walnut (Juglans nigra L.) seedlings of different geographic origins were planted in seven common garden plantations within the species' natural range in the midwestern United States. After 22 years, height, d.b.h., and survival measurements revealed that local trees (from within 100 miles north and south of the plantation) had the greatest survival at all locations, and those from areas 200 miles south of the planting site grew significantly taller than trees from more southerly locations. Survival in the Minnesota and Iowa plantations was highly correlated with latitude and longitude of seed source; northern and western seed sources had higher survival. Height and d.b.h. correlations were highly significant in all plantations. High heritabilities implied that much of the geographic variation in height and d.b.h. is under genetic control and that seed source selection should be included in black walnut improvement programs.