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Eugene K. Blythe and Jeff L. Sibley

‘Dwarf Burford’ holly (Ilex cornuta ‘Dwarf Burford’) is a significant nursery crop and is widely used in landscapes in U.S. Department of Agriculture hardiness zones 7 to 9. Stem cuttings can be rooted at multiple times during the year, provided cutting wood is sufficiently mature, with auxin treatments traditionally used to encourage rooting. This study was conducted to determine if auxin treatment could be eliminated, thus reducing labor and chemical requirements in the cutting propagation process. In three experiments, terminal stem cuttings of ‘Dwarf Burford’ holly were taken in winter, prepared with and without use of a basal quick-dip in an auxin solution, and rooted in a warm, high-humidity environment. Rooting percentages for nontreated cuttings and cuttings treated with 2500 ppm indole-3-butyric acid (IBA) + 1250 ppm 1-naphthaleneacetic acid (NAA) were similar, while treatment of cuttings with 5000 ppm IBA + 2500 ppm NAA resulted in a decrease in rooting percentage. The number of primary roots and total root length were similar among the three treatments, except in one experiment where total root length was greater with auxin-treated cuttings than with nontreated cuttings. Initial shoot growth responses were variable among the three experiments. The treatment of cuttings with auxin was not required for successful rooting and can be eliminated from the process for winter stem cutting propagation of ‘Dwarf Burford’ holly.

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Eugene K. Blythe

Confederate rose (Hibiscus mutabilis), a native of southeastern China, is an old-fashioned, ornamental plant often found in older gardens in the southern United States. Current breeding programs aim at developing selections with improved garden performance, thus providing new cultivars for nursery production. Hardy in U.S. Department of Agriculture (USDA) zones 7 to 9, plants grow as large shrubs or small trees in warmer areas, but generally die back to a woody base or short trunk in colder areas of their range. Stems from the past growing season that remain on plants during the winter in the warmer regions may be used to prepare hardwood stem cuttings. The current study examined hardwood cutting propagation of confederate rose in response to a 1-second basal quick-dip in auxin [1000 ppm indole-3-butyric acid (IBA), 3000 ppm IBA, 1000 ppm IBA + 500 ppm 1-naphthaleneacetic acid (NAA), and 3000 ppm IBA + 1500 ppm NAA] and a basal wound (along with 1000 ppm IBA only). Cuttings were rooted in a warm, high-humidity environment within a greenhouse. Auxin treatments improved overall rooting percentage and total root length, with 1000 ppm IBA (without and with a basal wound) providing the highest rooting percentages (about 70%) and nontreated cuttings the lowest (44%). A significant increase in total root length on rooted cuttings resulted with the use of 3000 ppm IBA (211 cm) and use of a basal wound plus 1000 ppm IBA (193 cm) compared with nontreated cuttings (87 cm). Auxin and wounding treatments did not have any significant inhibitory effects on budbreak and growth of new shoots on rooted cuttings.

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Eugene K. Blythe and Jeff L. Sibley

Auxin solutions prepared with sodium cellulose glycolate (SCG; a thickening agent, also known as sodium carboxymethylcellulose) and applied to stem cuttings using a basal quick-dip extend the duration of exposure of cuttings to the auxin and have previously been shown to increase root number and/or total root length on stem cuttings of certain taxa. In a series of three experiments, 3.75-cm stem sections (representing the bases of stem cuttings) of three ornamental plant taxa were dipped to a depth of 2.5 cm for 1 s in solutions prepared with selected rates of SCG using either deionized water or a 10% dilution of an alcohol-based rooting compound (Dip 'N Grow). Each stem section was weighed before and after being dipped in the solution. Regression equations were determined for each experiment and the rate of SCG providing the maximum ratio of SCG solution weight to stem piece weight was determined by setting the first derivative of the regression equation equal to zero. Maximum adhesion of solution was obtained using SCG at 13.35 to 13.71 g·L−1 with an average rate of 13.5 g·L−1.

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Eugene K. Blythe and Jeff L. Sibley

Heller’s japanese holly [Ilex crenata ‘Helleri’ (synonym: Ilex crenata f. helleri)] is a popular landscape plant in U.S. Department of Agriculture hardiness zones 5b to 8a because of its dwarf habit, slow growth rate, and dark green leaves. Plants can be propagated readily by stem cuttings and use of an auxin treatment is generally recommended to promote rooting. This study was conducted to determine if auxin treatment could be eliminated, thus reducing labor and chemical requirements in the cutting propagation process. In three experiments, terminal stem cuttings of Heller’s japanese holly were taken in winter, prepared both with and without use of a basal quick-dip in an auxin solution [2500 ppm indole-3-butyric acid (IBA) + 1250 ppm 1-naphthaleneacetic acid (NAA)], and rooted in a warm, high-humidity environment. Both nontreated cuttings and cuttings receiving a 1-second basal quick-dip in the auxin solution rooted at, or near, 100%. However, treatment of cuttings with auxin resulted in larger root systems on the rooted cuttings, which could allow earlier transplanting into larger nursery containers. No inhibition of new spring growth was exhibited by cuttings treated with auxin in comparison with nontreated cuttings.

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Ana Centeno and María Gómez-del-Campo

( Hartmann et al., 2002 ; Wiesman and Lavee, 1995 ; Zimmerman and Wilcoxon, 1935 ). In olive propagation from cuttings, IBA has been found to be the best root-promoting compound ( Hartmann, 1946 ). However, as a synthetic product, IBA is not permitted in