101 Propagation of Juglans cinerea L. (Butternut)

Abstract

Butternut trees are becoming endangered as a result of butternut canker disease; thus, it is desirable to propagate disease-resistant trees for screening and provenance tests. The objective of this study was to determine the conditions necessary for successful cutting propagation. In 1998, 10 trees were selected from a 4-year-old butternut plantation located in Rosemount, Minn. Hardwood cuttings were collected 30 Mar., 21 Apr., and 6 May. The auxins, indole-3-butyric acid-potassium salt (KIBA) in water at 0, 29, or 74 mmol·L-1 were tested for root induction. The basal end of cuttings were dipped in treatment solutions for 10 to 15 s and placed in a 1 peat: 1 perlite mixture in Deepots™ (D40) in a mist bed. Mist was applied for 5 s every 15 min. Greenhouse conditions were: 12-h photoperiod provided by high-pressure sodium lamps (60 μmol·m-2·s-1), 22 °C, and bottom heat of 27 °C (heating pads). Softwood cuttings were collected 20 May, 18 June, 30 June, and 23 July. Rooting treatment solutions and greenhouse conditions were the same as for the hardwood cuttings, except no heating pads were used. Rooted cuttings were planted in Treepots™ (10 × 10 × 36 cm) and gradually hardened off from the mist bed. Hardwood cuttings from the first two collection dates did not initiate roots. Best rooting (12.5%) was achieved on hardwood cuttings collected 6 May using 29 mmol·L-1 KIBA. Softwood cuttings rooted to some degree at all concentrations of rooting solution and at every collection date. The greatest rooting (70%) was achieved using 74 mmol·L-1 IBA. In general, best rooting percentages were achieved with softwood cuttings collected 18 June and 23 July and treated with 62 mmol·L-1 KIBA or 74 mmol·L-1 IBA. Both rooted hardwood and softwood cuttings were successfully acclimatized from the mist bed and many have initiated new growth.