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  • Author or Editor: Gary Blank x
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Two methods of application, the Danish Easy Roller and the German Sprühsystem, were tested to evaluate the effectiveness of naphthaleneacetic acid (NAA) at reducing leader growth (tips of primary axes) of fraser fir [Abies fraseri (Pursh) Poir.] Christmas trees. A commercial product, Sucker-Stopper RTU (1.15% ethyl 1-NAA), was applied to leaders at concentrations of 0 to 500 mL·L−1 when leaders were 8 to 15 cm long. As the concentration increased, leader elongation decreased. The Easy Roller reduced leader growth the most, but leader mortality was unacceptable at concentrations 20 mL·L−1 or greater. Although less effective than the Easy Roller, the Sprühsystem caused negligible mortality of leaders. Applying 40 mL·L−1 with the Easy Roller yielded ≈50% of leaders with target lengths of 20 to 36 cm with little mortality. The Sprühsystem gave similar results at 250 mL·L−1. NAA might be useful for producing dense trees with minimal shearing or for producing more natural, open trees during shorter rotations.

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The Top-Stop Nipper (TSN), a four-bladed, hand-held tool used to reduce leader growth in Christmas trees, was evaluated on fraser fir (Abies fraseri). The TSN placed incisions (nips) on the previous year's leader to reduce the amount of photosynthate transported to the developing leader. Treatments consisted of a control (zero nips), and one, two, three, or four nips at each of three stages of leader elongation (pre-budbreak, 2–3 cm, and 6–9 cm). The TSN significantly reduced leader elongation. The percentage of leaders that were within the target range of 8 to 14 inches (20.3–35.6 cm) increased from 18% for the control (no nips) to 46% with four nips. The TSN, when combined with traditional knife shearing or growth regulator treatments, might offer a method to produce dense trees with minimal shearing or to leave longer leaders to produce a more open “European-style” tree during a shorter rotation time.

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The Top-Stop Nipper (TSN), a four-bladed, hand-held tool developed for reducing leader growth of Christmas trees, was used as a wounding technique to reduce leader growth of Fraser fir (Abies fraseri). A regression model, based on an apical bud volume index (average bud diameter squared × length), was used to predict the number of nips to apply to each leader to yield a target length of 25 to 36 cm. Treatments included control trees (0 nips) and one to seven nips per leader. Nips were applied in May at budbreak. In an earlier study, increasing the number of nips decreased leader elongation when randomly applied to trees without regard to the size of the apical bud. In this study, when the number of nips increased with increasing bud volume index, leader growth was similar among all TSN treatments. Bud density (per unit length) on the 2006 leader increased with the number of nips applied to the 2005 leader. Results might be useful for growers who want to produce dense trees with minimal shearing or for growers who choose to leave a longer leader to produce a more open, “European-style” tree during a shorter rotation time.

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