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Wendy S. Klooster, Bert M. Cregg, R. Thomas Fernandez, and Pascal Nzokou

Traditionally, landscape conifers have been field-grown and sold balled and burlapped (B&B). Soil loss resulting from harvesting field-grown trees can be nearly 100 tons per acre for a 5-year rotation and harvest can only take place in the spring

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Amanda J. Taylor, R. Thomas Fernandez, Pascal Nzokou, and Bert Cregg

conventional, once-a-day irrigation. The objectives of this study were to 1) determine effects of cyclic irrigation programs on growth of container-grown conifers; and 2) explore underlying physiological mechanisms including various indicators of WUE. Materials

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Sidney Waxman

Seedlings obtained from mutations on conifer trees exhibit populations of dwarf shrubs. The general characteristics of the shrubs often differ from progeny to progeny. The most obvious difference between progenies is in annual rates of growth, with some showing growth rates 10 or more times greater than the slowest growing group. Differences that appear within each progeny include needle length, foliage coloration, branching habit and plant form. As a consequence, many interesting forms have been produced and named that are miniature, dwarf, and intermediate in size.

Variations in form include plants that are columnar, rounded, spreading, and weeping. Whereas variation in foliage color include blue-green, green, and gold.

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Ying Yang, Xian-Ge Hu, Bingsong Zheng, Yue Li, Tongli Wang, Anket Sharma, Huwei Yuan, and Jian-Feng Mao

different stresses to conifers and other gymnosperms ( Li et al., 2017 ; Liu and El-Kassaby, 2017 ). miRNAs generally bind to the 3′-UTR (untranslated region) of their corresponding target mRNAs and restrain protein production by destabilizing the mRNA and

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Nicholas A. Pershey, Bert M. Cregg, Jeffrey A. Andresen, and R. Thomas Fernandez

‘Zebrina’ was typically lowest with some exceptions. Table 2. Seasonal daily water use (DWU) (L per container per day) of four conifers grown in 10.2-L containers under four irrigation treatments administered 25 June –16 Oct. 2009 and 7 June –31 Oct. 2010

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John F. Ahrens, Larry J. Kuhns, Tracey L. Harpster, and Todd L. Mervosh

In 1995, Monsanto Chemical Co. announced that they would replace Roundup herbicide with Roundup Pro for use in the ornamentals and turf markets. Both products contain 4 lb a.i./gal glyphosate, but Roundup Pro contains a more-active surfactant. Though Roundup was labeled as a nonselective herbicide, dormant conifers were found to have varying degrees of resistance to it. Directed sprays that hit the lower two-thirds of many dormant conifers became common practice in the industry. Because the surfactant in Roundup Pro increases the activity of the glyphosate, a series of trials were initiated in 1996 in Connecticut, Pennsylvania, and Vermont in which four glyphosate formulations were applied to a variety of dormant conifers. Roundup, Roundup Pro, Glyfos, and Accord (with and without surfactant) were applied either over-the-top or as directed sprays to the lower 18 inches of the plants at rates between 0.5 and 3 lb a.i./acre. Plants treated included globe arborvitae; upright yew; Canadian hemlock; Colorado, Norway and white spruce; Douglas fir; eastern white pine; and balsam, Canaan, and Fraser fir. In a preliminary study, injury to the spruces in the form of dwarfed and chlorotic new growth was primarily associated with fresh pruning wounds. Accord plus surfactant and Roundup Pro injured more spruces than Roundup, but injury was slight. No injury was observed in upright yew with any formulation at rates up to 0.75 lb a.i./acre. Injury to arborvitae was greatest with Accord plus surfactant, intermediate with Roundup Pro, and least with Roundup. Results are inconclusive at this time, but the results of additional studies available early in the next growing season.will be presented.

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Karen E. Burr, Stephen J. Wanner, and Richard W. Tinus

It is not known when changes in primary direct heat stress tolerance of conifer seedlings occur in relation to other seasonally changing physiological parameters. This information should be incorporated into nursery practices and the matching of genotypes to landscape sites. Greenhouse-cultured, container-grown Douglas-fir, Engelmann spruce, and ponderosa pine. were cold acclimated and reacclimated in growth chambers over 19 weeks. Direct heat stress tolerance of needles, cold hardiness, and bud dormancy were measured weekly. Douglas-fir and Engelmann spruce heat stress tolerance increased with the development of new growth through one complete growth cycle, i.e., bud break, maturation, cold hardening, dehardening, and bud break the following growing season. Ponderosa pine differed in that new needles had intermediate tolerance, and fully cold hardy needles were the most intolerant. In none of the species did the timing of changes in heat stress tolerance coincide consistently with changes in cold hardiness or bud dormancy.

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Robert J. Richardson and Bernard H. Zandstra

producer level ( Klewano and Matthews, 2005 ). Conifer seedlings typically are grown in nurseries for 3 to 5 years before transplanting in production fields. After transplanting, trees take an additional 8 to 12 years to reach harvestable size. Due to the

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Larry Kuhns and Tracey Harpster

Though glyphosate is considered to be a nonselective herbicide, conifer growers have long known that under certain conditions, they could contact the lower branches of their trees with the herbicide Roundup without injuring them. Species, time of application, rate of application, surfactant, method of application, and pruning wounds are all factors affecting conifer tolerance to glyphosate. Because Roundup was widely used by conifer growers, they were very concerned when the formulation of Roundup was changed to contain a more active surfactant. The new product was marketed under the name Roundup Pro. This change increased its herbicidal activity and raised the possibility that it could damage trees if applied in the same way as Roundup. To determine the tolerance of conifers grown in the northeast to a variety of glyphosate formulations, and sulfosate, a set of studies was established. Roundup, Roundup Pro, Glyfos, Accord, and Sulfosate were all applied to field grown hemlock, white fir, Canaan fir, fraser fir, douglas fir, Colorado spruce, and eastern white pine. Rates of 1 to 3 lb active ingredient/A were applied in the fall after new growth was hardened off. In general, it was found that the risk of injuring trees with Roundup Pro is greater than with the old formulation of Roundup. However, in all cases in which Roundup Pro caused more injury than Roundup, the Roundup Pro was applied at 3 lb active ingredient/A. This rate is double the rate recommended for this use. In calibrated, directed spray applications at 1.5 lb active ingredient/A or less, Roundup Pro should be safe for use around the species tested after their growth has fully hardened in the fall.

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Karen E. Burr, Stephen J. Wallner, and Richard W. Tinus

Greenhouse-cultured, container-grown seedlings of interior Douglas fir [Pseudotsuga menziesii var. glauca (Beissn.) France], Engelmann spruce [Picea engelmannii (Parry) Engelm.], and ponderosa pine (Pinus ponderosa var. scopulorum Engelm.) were acclimated and deacclimated to cold in growth chambers over 19 weeks. Heat tolerance and cold hardiness of needles, and bud dormancy, were measured weekly. Heat tolerance of Douglas fir and Engelmann spruce needles increased with development through the first complete annual cycle: new needles on actively growing plants; mature needles, not cold-hardy, on dormant plants; cold-hardy needles on dormant and quiescent plants; and mature, needles, not cold-hardy, on actively growing plants. Heat tolerance of ponderosa pine needles differed in two respects. New needles had an intermediate tolerance level to heat, and fully cold-hardy needles were the least tolerant. Thus, the physiological changes that conferred cold hardiness were not associated with greater heat tolerance in all the conifers tested. In none of these species did the timing of changes in heat tolerance coincide consistently with changes in cold hardiness or bud dormancy.