The American chestnut [Castanea dentata (Marsh.) Borkh.] was decimated by an exotic fungus [Cryphonectria parasitica (Murr.) Barr] in the early 1900s. Breeding efforts with American and Chinese chestnuts (C. mollissima Blume) produced putatively blight-resistant progeny (BC₃F₃) in 2007. We compared two nut size classes for differences in seedling quality of bare-root stock grown in commercial nurseries. We compared the BC₃F₃ generation to parental species and other generations. Nuts in the large size class produced taller trees than nuts in the small size class, but sizing nuts prior to sowing did not reduce variability in nursery seedling size. Results indicate that overall seedling quality could be improved by culling small nuts, but seedling uniformity would only be improved by culling seedlings before planting. We recommend refinement of restoration efforts to match seedling size to site type and planting goals. BC₃F₃ chestnuts differed from Chinese chestnuts in 67% of tests, and were different than American chestnuts in half the tests, indicating not all American traits were recovered in this early phase of seedling development. Family differences within the BC₃F₃ generation were most apparent for mean nut weight, and only one BC₃F₃ family differed from other BC₃F₃ families in seedling growth characteristics.

The ability to restore American chestnut (Castanea dentata) through the planting of blight-resistant (Cryphonectria parasitica) trees is currently being tested. Forest-based research on the species’ silvicultural requirements and chestnut blight development are lacking. Pure American chestnut seedlings were planted in a two-age shelterwood forest with low residual basal area and in a midstory-removal treatment with high residual basal area. Survival did not differ between silvicultural treatments and averaged 67 percent across both treatments by the fifth year. Trees in the two-age shelterwood were 2.36 m and 16.8 mm larger in height and ground-line diameter, respectively, compared to trees in the midstory-removal by the fifth growing season. Blight occurrence was not affected by silvicultural treatment. Exploratory analyses indicated that seedling grading at planting and keeping trees free-to-grow through competition control would have resulted in a two-year gain in height and GLD growth in the two-age shelterwood treatment. The two-age shelterwood represented the most efficacious prescription for chestnut restoration, but the midstory-removal prescription may offer a reasonable alternative in areas where harvesting must be delayed.

Blight-resistant American chestnut (Castanea dentata) may soon be commercially available, but few studies have tested methods to produce high quality seedlings that will be competitive after planting. This study evaluated the performance of one American, one Chinese (C. mollissima), one second-generation backcross (BC₃F₂), and 10 third-generation backcross chestnut families (BC₃F₃). We examine growth over one year in a commercial tree nursery in east Tennessee. We examined relationships among nut size and weight and seedling growth, between germination timing and seedling survival, and between germination percentage and growth. Across the population tested, a 1 g increase in nut weight corresponded to a 6 cm increase in seedling height, a 0.5 mm increase in root collar diameter and one additional first order lateral root, but models had low predictive power. BC₃F₃ chestnuts grew similarly to American chestnuts, with substantial differences in growth among chestnut families within generation. Nuts that germinated by 23 April had greater than 1955 odds of surviving the first growing season than nuts that germinated in late May. American and backcross chestnut growth slowed in late June, presumably due to exhaustion of their cotyledons before leaf expansion. These results will help nursery managers refine cultural practices to maximize growth of backcross chestnuts.