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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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Deepu Mathew, Zakwan Ahmed and N. Singh

The phenomenon of flowering and aerial bulbil production in Asiatic garlic was observed under long photoperiodic conditions of Ladakh, India. Flowers were sterile and the bulbils produced on the umbel were true to type. Observations on a large number of flowering and nonflowering plants have led to the formulation of a precise flowering index (FI) in garlic. Plants with a minimum leaf number of 7, height 25 cm, collar width 0.6 cm, bulb diameter 3.7 cm, bulb weight 22.5 g, and functional leaf area of 182.4 cm2 had only shown the flowering. The flowering index formulated was a product of leaf number, plant height, functional leaf area, and bulb weight. For flowering, FI should be more than 788, and availability of a minimum photoperiod of 4020 hours during a growth period of 11 months was another prerequisite. Nonfulfillment of any one of the factors of flowering, although FI and photoperiod were satisfactory, led to nonflowering. Garlic aerial bulbil yield was positively correlated with leaf number, plant height, bulb weight, bulb diameter, length of flower stalk, 100 seed weight, and head diameter. Following the multiple regression model y = –11.9 – (0.00031 × number of bulbils) + (0.147 × 100 bulbil weight) + (4.95 × head diameter) + (0.0460 × length of flower stalk), aerial bulbil yield prediction was possible at a mean accuracy of 87%.

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Jyotsna Sharma, Gary W. Knox and Maria Lucia Ishida

Certain cultivars of magnolia are desirable in landscapes for their uncommon yellow flowers. While cultivars derived from Magnolia acuminata L. (cucumbertree magnolia) are difficult to propagate by stem cuttings, some with mixed parentage appear easier to propagate in this manner. We propagated six yellow-flowered cultivars vegetatively by applying 0, 8, 16, or 30 g·kg–1 (0, 8,000, 16,000, or 30,000 ppm) indole-3-butyric acid (IBA) in talc to bases of terminal stem cuttings collected 5, 7, 9, or 11 weeks after budbreak. Mean rooting percentage over all cultivars increased from 12% (in the absence of IBA) to 34% (after application of 30 g·kg–1 IBA). Rooting percentage and basal stem diameter of a cutting did not seem related. For each collection date, more cuttings of `Ivory Chalice' and `Yellow Lantern' developed roots than the other cultivars. More roots (mean = 5) developed on cuttings of `Yellow Lantern' collected 5 weeks after budbreak or when treated with 30 g·kg–1 IBA than the other cultivars. `Butterflies' largely remained unresponsive, whereas rooting of `Golden Sun,' `Hot Flash,' and `Maxine Merrill' collected 5 weeks after budbreak was 31%, 22%, and 28%, respectively. When data were analyzed separately for selected cultivars, 63% rooting was observed among cuttings of `Ivory Chalice' collected 7 weeks after budbreak. Rooting percentage was higher (22%) among cuttings of `Hot Flash' collected 5 or 7 weeks after budbreak in comparison to later collection dates, but harvest date did not influence rooting of `Yellow Lantern,' which ranged from 44% to 59%. Collection of stem cuttings early in the growing season (5 weeks after budbreak) was beneficial (31% rooting) for inducing rooting among cuttings of `Golden Sun.' We conclude that `Ivory Chalice' and `Yellow Lantern' are promising choices for growers interested in clonal propagation of yellow-flowered cultivars of magnolia. To maximize rooting among these cultivars, terminal cuttings should be collected within 5 to 11 weeks after budbreak and treated with 16 or 30 g·kg–1 IBA in talc. Early collection dates (5 to 7 weeks after budbreak) improved rooting among cuttings of other cultivars but these, particularly `Butterflies,' remain variably recalcitrant and merit further study.

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Gregory L. Reighard, David W. Cain and William C. Newall Jr.

More than 400 genotypes of Prunus were evaluated for “in field” rooting and survival from fall-planted hardwood cuttings treated with 2000 ppm IBA. Cultivars of European and Japanese plums originating from species and interspecific hybrids of the section (sect.) Prunus had the highest survival. Cuttings from cultivars of sand cherry (sect. Microcerasus) and peach (sect. Euamygdalus) averaged 28% to 54% lower survival than European and Japanese plums. Few cultivars of almonds (sect. Euamygdalus), apricots (sect. Armeniaca), and American plums (sect. Prunocerasus) rooted from hardwood cuttings. Chemical name used: 1H-indole-3-butyric acid (IBA).

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L. Eric Hinesley and Layne K. Snelling

Stem cuttings of Atlantic white cedar [Chamaecyparis thyoides (L.) B.S.P.] were collected in early June 1995, divided into two parts (distal tip and proximal segment), and rooted for 12 weeks in shaded containers outdoors. Total rooting was near 80%. Mist intervals of 8 and 15 min yielded the best rooting percentages and the least dieback and injury. Two rooting media were tested, with similar results. Rooting was slightly higher in Spencer-Lemaire Rootrainers (Hillson size), compared to RoPak Multi-pots (#45). More than 90% of the tips rooted, even without IBA treatment. Auxin improved rooting of stem segments, but the difference between IBA at 1.5 and 3.0 g·L-1 was small. Yield of cuttings suitable for transplanting or potting was 80% for tips, 58% for segments. Dividing stem cuttings into two or more parts allows multiplication of rooted propagules from a collection. Chemical name used: 1H-indole-3-butyric acid (IBA).

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Paul H. Henry and John E. Preece

Vegetative shoots were forced in the greenhouse from excised stem (branch) sections of dormant Japanese maple (Acer palmatum Thunb.), red maple (Acer rubrum L.), and sugar maple (Acer saccharum Marsh.). Softwood shoots generated in this way were used as stem cuttings in a subsequent adventitious rooting study. Data indicate that maple shoots can be forced using this technique, but that both the percentage of stem sections forming shoots and the number of shoots produced are highly variable among both species and clones. Whereas Japanese and red maple formed shoots on >50% of stem sections, shoots were generated on only 20% of sugar maple stem sections. Significant variability was also observed in rooting response, with red maple shoots rooting at much higher percentages (60%) than either Japanese maple (26%) or sugar maple (15%).

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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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J.J. Le Roux and J. Van Staden

Two cold-tolerant species (Eucalyptus macarthurii Deane et Maiden and E. smithii R.T. Baker), a cold-tolerant hybrid (E. macarthurii×E. grandis Hill ex Maiden), and E. saligna Sm. were propagated in vitro from nodal explants collected from field-grown seedlings and from clonal hedges. Shoot growth was initiated on modified Murashige and Skoog (MS) medium containing BA at 0.1 mg·liter-1. Modified MS medium with BA (0.2 mg·liter-1) and NAA (0.01 mg·liter-1) was most effective in promoting shoot proliferation. Root initiation was achieved on half-strength modified MS medium with 2 mg IBA/liter. Rooted plants were hardened and established in the field. Chemical names used: N-(phenylmethyl)-1EZ-purin-6-amine (BA); 2-(1-naphthyl)acetic acid (NAA); 1H-indole-3-butyric acid (IBA).

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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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James A. Schrader and William R. Graves

Alnus maritima (Marsh.) Nutt. (seaside alder) is a rare, woody-plant species with potential for use in managed landscapes. Information on the propagation and production of this species is not available. Our objective was to evaluate the use of softwood cuttings to propagate A. maritima, with emphasis on how indole-3-butyric acid (IBA), plant provenance, and time of collection affect cutting survival, rooting percentage, the number of roots produced, and their length. Propagation trials were conducted with cuttings from seven trees on the Delmarva Peninsula (Eastern Shore of Maryland and southern Delaware) and seven trees in Oklahoma. Cuttings from mature plants in both provenances were collected on 14 June and 23 Aug. 1998; wounded; treated with IBA at 0, 1, or 8 g·kg-1; and placed under intermittent mist in a greenhouse for 9 weeks. Use of IBA at 8 g·kg-1 caused a greater rooting percentage (68%), root count (7.2), and root length (39.2 mm) than did the other IBA rates when applied to cuttings from Oklahoma in June, but IBA had little effect on cuttings from the Delmarva Peninsula. Across IBA treatments, rooting of cuttings from Oklahoma (55% in June and 12% in August) was greater than the rooting of cuttings from Delmarva (27% in June and 3% in August). Cuttings from Oklahoma had greater survival, callus development, root length, and root count than did cuttings from the Delmarva Peninsula during June and August trials. Averaged over IBA treatments and provenances, cuttings collected on 14 June rooted more frequently (41%) than did cuttings collected 23 Aug. (8%). We conclude that softwood cuttings from mature plants are an effective way to multiply clones of A. maritima, particularly when cuttings are collected early in the season and treated with IBA at 8 g·kg-1.