Effects of Substrates, Wounding, and Hormone Concentrations On Vegetative Propagation of Baldcypress

In previous studies, baldcypress [Taxodium distichum (L.) L.C. Richard] clones were selected for tolerance to high pH soils, drought and foliar or soil salt exposures, and/or ornamental characteristics.  The objective of the current research was to determine the treatment combinations that yielded optimum root quantity (percentage) and quality (root number, length and mass) for selected clones.  Cuttings were treated with one of four K-IBA (potassium salts of indole-3-butyric acid) concentrations (0, 5,000, 10,000, 15,000 mg·L^-1), wounded or not wounded (1 cm long basal incision) and rooted in one of three substrates (100% perlite, 100% peat moss, or 50% perlite : 50% peat moss).  Data indicated a trade-off between potential rooting quantity and root quality measures when considering the effects of substrate.  While rooting percentages were significantly affected by substrates only at P≤ 0.10 (53% in 100% perlite versus 36% in 100% peat moss), there were highly significant (P≤ 0.0001) differences in rooted cutting potential among substrates, as measured by the percentage of cuttings with basal callus.  Cuttings placed in 100% perlite callused at 85 %, while cuttings placed in 100% peat moss callused at approximately 53%.  Conversely, the 100% peat moss treatment yielded cuttings with significantly greater root quality for all measures, except root number per cutting.  Wounding cuttings proved to have deleterious effects on root quality measures.  Total root length was approximately 30% greater for non-wounded cuttings than for wounded cuttings.  Increasing K-IBA concentrations did not significantly affect rooting or callus percentages, but did significantly affect root dry mass, total root length, and average root length per cutting.  Total root length increased from 10.8 cm at 0 mg·L^-1 K-IBA to 16 cm at 15,000 mg·L^-1 K-IBA.  Results suggest that high quality baldcypress cuttings should not be wounded, should be treated with 15,000 mg·L^-1 K-IBA, and grown in a substrate with intermediate water holding capacity to achieve an acceptable balance between rooting percentage and rooted cutting quality objectives.