On 10 Apr. 1997, the smaller branch on forked Fraxinus americana L. (white ash) trees in an 8-year-old clonal plantation were removed, cut into 25-cm-long stem sections, and placed horizontally in perlite under seven different forcing regimes. Sprouts from latent buds were excised 67 and 99 days later and trimmed to retain the apical pair of leaves and terminal bud. The basal 2 cm of each cuttings was set for 30 to 60 min in one of six aqueous dilutions made from a stock solution of 1% IBA and 0.5% NAA (Dip `n Grow) before placing in a 1 perlite: 1 vermiculite medium. Eight weeks after treating, cuttings data were collected. Most cuttings treated with 3200 mg/L IBA plus 1600 mg/L NAA quickly died. Survival (85%) and rooting percentage (86%) were similar for the remaining auxin-treated cuttings and controls with water only. Cuttings treated with 1600 mg/L IBA plus 800 mg/L NAA produced the most adventitious roots (6.2 roots), the longest adventitious root (22 cm), and longest combined sum of all adventitious roots (51 cm); however, these rooted cuttings died when transplanted to soil. Cuttings treated with 100 mg/L IBA plus 50 mg/L NAA or 400 mg/L IBA plus 200 mg/L NAA had more adventitious roots (3.2 roots) and total length of adventitious roots (370 mm/cutting) than cuttings treated with 40 mg/L IBA plus 20 mg/L NAA or controls with water only (2.2 roots, 220 mm long). Results indicate softwood cuttings forced on stem segments of adult white ash readily root under mist following a brief soak in a 400 mg/L IBA plus 200 mg/L NAA solution.
Optimizing Conservation Strategies for a Threatened Tree Species: In Situ Conservation of White Ash (Fraxinus americana L.) Genetic Diversity through Insecticide Treatment
