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- Author or Editor: Daniel K. Struve x
A method is described for producing bare-root shade tree whips in containers. Whip production is begun in February in heated greenhouses by sowing seed. Seedlings are transplanted to copper-treated containers and grown in a greenhouse until May, when they are moved outdoors and transplanted to No. 3 copper-treated containers. In October (8 months after seeding), plant heights range from 1 to 2 m. Several media have been developed that result in rapid growth, while separating readily from the root system by hand-shaking. Bare-root plants placed in refrigerated storage for 6 months and repotted, retained high survival and regrowth potential. The system combines the handling ease of bare-root stock with the high survival and regrowth potential of container stock.
The effectiveness of a paclobutrazol/paint mix in controlling growth of poinsettia plants (Euphorbia pulcherrima) cultivars Freedom Red and Angelica Red was evaluated. Plants were grown in containers whose interior walls were coated with a flat latex impregnated with varying concentrations of paclobutrazol: 0, 5, 20, 80, 100, 150, 200, and 300 mg·L–1 (0. 0.032, 0.128. 0.512, 0.64, 0.96, 1.28, and 1.92 mg a.i. per container, respectively). As a comparison, one treatment consisted of plants drenched with 118 ml/container of a paclobutrazol solution at 3 mg·L–1.
Plants grown in containers with the paint–paclobutrazol mix were shorter than the control plants. Treatments involving concentrations of 100 mg·L–1 or more (even as much as doubled or tripled) did not produce proportionately shorter plants. Root dry weights of plants in all treatments were not significantly different. However, the length of roots touching the internal surface of the container decreased with increasing growth regulator concentrations. This may help explain why doubling concentrations of growth regulator-in-paint does not produce proportionately shorter plants: roots start absorbing the growth regulator as soon as they touch the wall of the container. As a consequence, all root elongation is reduced, resulting in less root-growth regulator contact and less growth regulator uptake. More measurements of root length and root area are required in order to proof this hypothesis. When paclobutrazol concentrations were higher than 100 mg·L–1, some bracts showed evidence of “crinkling.”
Three- to 4-cm caliper pin oak (Quercus palustris Muenchh.), a species considered easy to transplant, had greater total root length and more first, 2nd, and 3rd order lateral roots than similar sized scarlet oak (Q. coccinea Juench.), a species considered difficult to transplant. One-year-old seedlings initiated roots 2 weeks earlier in spring and regenerated more roots after 12 weeks than did scarlet oak. Girdled, dormant scarlet oak seedlings regenerated similar numbers of roots as ungirdled plants, while girdled, dormant pin oak seedlings regenerated fewer roots. Removing buds from dormant seedlings decreased root regeneration by pin oak, but had no effect with scarlet oak.
Seedlings of nine coarse-rooted species–sawtooth oak (Quercus acutissima Carruth), white oak (Q. alba L.), cherrybark oak (Q. falcata var. pagodifolia Elliott), post oak (Q. stellata Wangenh.), black walnut (Juglans nigra L.), pignut hickory [Carya glabra (Mill.) Sweet], pecan [C. illinoinensis (Wangenh.) C. Koch], Chinese chestnut (Castanea mollissima Blume), and common baldcypress [Taxodium distichum (L.) L. Rich]—were grown for one growing season in nontreated containers or in containers treated on their interior surfaces with white interior latex paint containing 100 g Cu(OH)2/liter. Seedlings of each species and container treatment were harvested twice: once after being transplanted from 3.2- to 15.0-liter containers and at the end of the growing season. Cupric hydroxide-treated containers decreased the amount of circled, kinked, and matted roots formed at the container wall-medium interface in all species tested. Plants grown in Cu(OH)2-treated containers also had altered root dry-weight partitioning. The partitioning patterns were species specific and included 6% to 20% increases in the percentage of root dry weight in interior vs. exterior portions of the rootball (white oak, black walnut, Chinese chestnut, and baldcypress), 10% to 21% increases in the percentage of root dry weight in upper vs. lower halves of the rootball (sawtooth oak, cherrybark oak, black walnut, and baldcypress), and an increase in the percentage of primary lateral roots (lateral roots originating from taproots or roots functioning as taproots) on the upper (proximal) half of taproots (cherrybark oak, pecan, and baldcypress). Nutrients in leaves, stems, and roots of sawtooth oak seedlings were analyzed at both harvests. Seedlings grown in Cu(OH)2-treated containers had more Cu in most plant tissues than nontreated seedlings. Also, seedlings grown in Cu(OH)2-treated containers had higher total Ca and Mg concentrations at transplanting and higher total N and Zn concentrations at the end of the growing season than nontreated seedlings.
Water is quickly becoming one of the world's most precious resources. Micro- and cyclical irrigation are two effective ways that reduce irrigation volume without reducing plant quality. Development of a control mechanism to deliver timely and appropriate irrigation volumes combined with the advantages of micro- and cyclical irrigation will allow maximum water conservation and plant quality. For container-grown nursery plants, the interaction of container geometry and media physical properties dictate the volume of water available for plant uptake. The maximum amount of water a container substrate can hold under gravity is container capacity (CC). We managed season-long irrigation volumes by maintaining CC at three levels; 100% CC; 80% CC; and 60% CC, and used a set irrigation as a commercial control. The results showed similar plant growth for the 100% and set irrigation control groups through the growing season. However, the scheduled regime applied 50% more water than the group maintained at 100% CC. Our system increased water use efficiency without decreasing plant quality.
In nursery production, increased branching is desirable, especially when growing stock that will be marketed at smaller sizes. Typically, branching is increased by pruning, which reduces growth potential. As an alternative to mechanical pruning, a chemical branching agent, Cyclanilide, has been evaluated for its ability to increase branching in container-grown whip production systems. Cyclanilide sprays of 0, 50, 100, and 200 mg·L-1 were applied to elongating shoots of Acer ×freemanii `Jeffsred', Cercis canadensis, Diospyros virginiana, Eucommia ulmoides, Malus ×`Prairie Fire', Malus ×`Harvest Gold', and Quercus rubra whips. Branching was increased in all taxa except Eucommia at concentrations >100 mg·L-1, without significantly reducing plant dry weight. For Diospyros, branching was increased when combined with pruning before Cyclanilide application.
The effectiveness of two application methods of the growth regulator paclobutrazol on the growth of Chrysanthemum plants, Dendranthema ×grandiflora (Ramat) (cv. `Fina' and `Cream Dana') were compared. Plants were grown in containers with their interior covered by a mixture of flat latex paint and several concentrations of paclobutrazol (0, 5, 10, 20, 40, 80, 100, 150, 160, and 200 mg·L–1) or were treated with a soil drench of the growth regulator according to label recommendations (59 ml/container of paclobutrazol solution at 4 mg·L–1). Plants grown in containers with the paint–paclobutrazol mix at concentrations >80 mg·L–1 were shorter than plants given the control and paint only treatments but taller than plants given the drench treatment. Increasing paclobutrazol concentrations in paint from 100 to 150 and 200 mg·L–1 did not produce proportionately shorter plants. Paint alone had no effect on growth and development. Plants subject to growth regulator treatments appeared greener than the control plants. None of the plants given treatments with paint with or without paclobutrazol showed any sign of phytotoxicity. These results suggest the possibility of a new application method for systemic chemicals with the potential of reducing or eliminating worker protection standard restricted entry intervals and reducing the release of chemicals to the environment. Chemical name used: beta-[(4-chlorophenyl)methyl]-α-(1,1-dimethyl)-1H-1,2,4,-triazole-1-ethanol (paclobutrazol).
Dormant 1-year-old bare-root green ash (Fraxinus pennsylvanica Marsh.) seedlings were grown in CuCO3-treated (inner surfaces of plastic containers were painted with 100 g CuCO3/liters flat-white exterior acrylic latex paint) and untreated plastic containers to study the effects of CuCO3 on root growth. Plants grown in CuCO3-treated containers were nearly 50% taller than plants grown in untreated containers (119 vs. 81 cm, respectively). Root contacting CuCO3-treated surfaces had near zero elongation rates within 3 days. Roots inhibited by contacting CuCO3-treated surfaces were not killed and resumed elongation rates similar to non-CuCO3-treated roots within 3 to 6 days of release from CuCO3. Roots contacting CuCO3-treated surfaces were 50% shorter (14 vs. 28 cm), branched closer to the root apex (2.4 vs. 4.7 cm), and had more higher-order lateral roots (10.6 vs. 7.6) than roots contacting untreated container surfaces. Seedlings grown in CuCO3-treated containers had higher Cu concentrations in main roots, root tips, stems, and foliage than seedlings grown in untreated containers.
Softwood cuttings of ‘Red Sunset’ red maple (Acer rubrum L.) were given 3-sec basal dips in five auxins at four concentrations. Auxins used were: IBA, K-IBA, NP-IBA, P-ITB, and P-IBA. All auxins were prepared in 10-, 20-, 30-, and 40-mm concentrations. Cuttings treated with 30 mm IBA had the highest percentage of rooting (70%). Other treatments exceeding 50% rooting were: 20 mm K-IBA and IBA and 30 mm P-IBA and P-ITB. Although the percentage of rooting was less in cuttings treated with aryl esters of IBA, rooted cutting quality was improved when compared with IBA-treated cuttings. Cuttings treated with 30 and 40 mm P-IBA had more roots per rooted cutting (two to three) and more total root length (20 cm) compared with 30 mm IBA-treated cuttings. Chemical names used: 1H-indole-3-butanoic acid (IBA); potassium salt of IBA (K-IBA); N phenyl-indole-3-butyramide (NP-IBA); phenyl indole-3-thiobutyrate (P-ITB); and phenyl indole-3-butyrate (P-IBA).