GA 4+7Soak Before Cold Stratification Enhances Juglans NigraSeedling Production

Abstract

Eastern black walnut ( Juglans nigraL.) seeds typically require a long period of stratification and often have low germination. A study was conducted to evaluate the effect of three formulations of gibberellic acid at 250 mg·L ^-1or tap water as a soaking treatment for ‘Thomas’ black walnut seeds for 24 h before stratification for 30, 45, 60, 75, or 90 d. Gibberellic acid treatments included 1) GA ₃(ProGibb®); 2) GA ₄₊₇(Provide®); and 3) 6-benzyladenine (BA) + GA ₄₊₇(Promalin®). Percent walnut shoot emergence 60 days after planting, days to 20% and 80% shoot emergence (E20 and E80), and early seedling growth from black walnut seeds were evaluated. Percent shoot emergence was always higher for seeds soaked in GA ₄₊₇or BA + GA ₄₊₇when compared with other treatments. Shoot emergence for some seeds soaked in GA ₄₊₇and BA + GA ₄₊₇occurred with 30 d stratification and percent emergence increased with longer stratification periods. Seeds soaked in GA ₃had higher percent shoot emergence than those soaked in tap water only. Also, seeds soaked in GA ₃had fewer days to 20% shoot emergence when stratified for 45 or 60 d than those soaked in tap water and stratified for the same period of time. Addition of BA at 250 mg·L ^-1apparently did not enhance percent shoot emergence, E20, E80, or seedling height or weight. With timely harvest, hulling, seed selection, and soaking walnuts with 250 mg·L ^-1GA ₄₊₇followed by 90 d stratification, 82% shoot emergence (i.e., germination) was attained.