Date of Award
Master of Science
G. Shannon Smith
John Day, Effin T. Graham
Cuttings of ten woody ornamentals were treated with acid (10 sec. dip in 2N H2SO4) and base (10 min. soak in NaOH pH 10.5) alone and in combination with two rates of IBA (1,000 and 3,000 or 8,000 ppm talc formulation) to determine pretreatment effects on percent rooting, root quality grade, root ball diameter, and root dry weight at three seasons. Five acid tolerant species (Cornus florida, Tsuga canadensis, Rhododendron obtusum 'Coral Bells', Ilex cornuta 'Burfordii', Juniperus horizontalis 'Bar Harbor') and five base tolerant plants (Juniperus conferta, Juniperus virginiana, Cercis canadensis, Philadelphus coronarius, Euonymus japonicus) were tested as softwood (Spring), semi-hardwood (Fall) and hardwood (Winter) cuttings to determine treatment effects but also to detect any correlation between pH tolerance and chemical treatment could be observed. Rooting parameters were correlated to see if a measure less laborious than dry weight could be adopted.
The majority of species had highest correlation coefficients between root quality grade and root ball diameter. These two parameters also correlated well with dry weight but coefficients varied from season to season and even among treatments. Thus, several parameters were used to evaluate rooting of most species.
Dry weight and root quality grade showed obvious differences in seasonal rooting. Euonymus was easily rooted at any season; shore juniper, mockorange and dogwood rooted best in spring; Burford holly and 'Bar Harbor' juniper in winter; and azalea in the fall. Red Cedar rooted very poorly and redbud and hemlock not at all. Averaged over all species rooting was generally better in spring followed by fall and winter.
The treatment giving best rooting for the fall experiment was high IBA. For winter hardwood cuttings, best treatments were IBA at either rate and combinations of IBA + base. Spring softwood cuttings rooted best when treated with high IBA, base + high IBA, base + low IBA and, usually, low IBA.
Best treatments for acid tolerant plants were base + high IBA, high IBA and base + low IBA. However, there was no obvious trend where base alone significantly increased rooting of acid-tolerant species. Base-tolerant species reacted much the same as acid-tolerant plants. Best response occurred with high IBA, base + high IBA, low IBA and base + low IBA. Acid treatment did not increase rooting of the base-tolerant plants tested.
Treatments which gave consistently best results for Euonymus japonicus were low or high IBA, acid + high IBA and base + high IBA. Best treatments for Juniperus horizontalis 'Bar Harbor' were base, high IBA, acid + high IBA, base + low or high IBA and even control plants were acceptable. Consistently good rooting occurred for Juniperus conferta treated with high or low IBA. Juniperus virginiana rooted only slightly in the winter with best results occurring with high IBA, or base + high IBA. Best treatments for Ilex cornuta were base, base + high IBA, low IBA and high IBA. For Philadelphus coronarius high IBA and base + high IBA gave best results. No significant differences due to treatments were recorded for Rhododendron obtusum 'Coral Bells'. For Cornus florida high IBA and base + high IBA were found to be superior treatments.
The single best treatment for Juniperus virginiana, Philadelphus coronarius, Rhododendron obtusum 'Coral Bells', Ilex cornuta 'Burfordii', and Cornus florida was base + high IBA. Euonymus japonicus and Juniperus conferta rooted best under high IBA. For Juniperus horizontal is 'Bar Harbor' base alone was the single best treatment. Both Tsuga canadensis and Cercis canadensis failed to root in any season regardless of chemical treatment.
McCrary, Scott J., "Seasonal rooting, as measured by four parameters, of ten woody ornamentals treated with acid (H₂SO₄), base (NaOH) and IBA. " Master's Thesis, University of Tennessee, 1980.