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  • Author or Editor: A-M. Boland x
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The expansion of urban communities to rural areas is leading to an increase of the problem of deer damage. White-tailed deer (Odocoileus virginianus) damage to landscape plants in commercial nurseries, residential and public areas is very widespread. Thuja occidentalis (Arborvitae) is one of the most common landscape plants. It is widely produced by nurseries and used by homeowners in the landscape. However, it is also highly favored by deer for browsing. Thuja plicata (Arborvitae) the Western Cedars is a highly deer-resistant arborvitae. One of the principal limiting factors for new arborvitae for its success in nursery productionand its use in the landscape is cold hardiness (in northern climates). However, the cold hardiness of different Thuja plicata is not known. Deer-resistant Thuja plicata cultivars: `Atroviren', `Cancan', `Elegantissima', `Excelsa', `Gelderland', `George Washington', `Hilleri', `Sunshine', and `Virescens' planted in Sprintg 1998 at The Morton Arboretum research plot in Lisle, Ill. Branch cold hardiness was tested by artificial freezing in Jan. 1999 and 2000. Ice-nucleated samples were placed in an ultra-low temperature and kept at 2 °C overnight, and the temperature then lowered at 5 °C/h to –40 °C, at which time samples were taken out at each test temperature (at 4 °C intervals). After the freezing test, the samples were thawed at 4 °C for 24 h, then planted in a peat and perlite media and kept at 100% humidity in a greenhouse. Samples were evaluated after 2 weeks for visual browning and lowest survival temperature. There were significant differences in coldhardiness between the nine cultivars tested in Jan. 1999. `Elegantissima', `Excelsa'. and `Cancan' were the most hardy (–34 to 40 °C), followed by `Virescens', `Sunshine', and `Gelderland' (–27 to 32 °C), `Hilleri' and `Atrovirens' (–24 to 25 °C). `George Washington' ` was the least hardy (–20 °C) cultivar.

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Individual and interactive effects of restricted root volume (RRV) and regulated deficit irrigation (RDI) on vegetative growth and mineral nutrition of peach trees [Prunus persica (L.) Batsch (Peach Group) `Golden Queen'] were studied over 3 years (1992-95). Trees were grown in lysimeters of five different volumes (0.025, 0.06, 0.15, 0.4, and 1.0 m3) with either full or deficit (RDI) irrigation. Increasing soil volume increased vegetative growth as measured by trunk cross-sectional area (TCA) (linear and quadratic, P < 0.011) and tree weight (linear, P < 0.001) with the final TCA ranging from 29.0 to 51.0 cm2 and tree weight ranging from 7.2 to 12.1 kg for the smallest to largest volumes. Root density measured at the completion of the experiment decreased with increasing soil volume (linear and quadratic, P < 0.001) with root length density declining from 24.0 to 2.0 cm·cm-3. RDI reduced vegetative growth by up to 70% as measured by weight of summer prunings. Root restriction was effective in controlling vegetative vigor and is a viable alternative for control of vegetative growth. Mineral nutrition did not limit tree growth.

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Individual and interactive effects of restricted root volume (RRV) and regulated deficit irrigation (RDI) on productivity and water use of peach trees [Prunus persica (L.) Batsch `Golden Queen'] were studied over 3 years (1992-95). Trees were grown in lysimeters of five different soil volumes (0.025, 0.06, 0.15, 0.4, and 1.0 m3) with either full or deficit (RDI) irrigation. In Years 3 and 4, fruit size was reduced by up to 30% on trees in the two smallest volumes. Tree water use was positively related to increasing soil volume (linear, P < 0.001; quadratic, P < 0.011) in all years ranging from 1.8 to 4.4 L·mm-1 Epan in the post-RDI period of Year 2. Water use of deficit-irrigated trees was less than fully irrigated trees and there was an interaction between soil volume and irrigation treatment during RDI. Water relations did not limit growth or productivity. Tree water use was reduced under root restriction as a consequence of canopy demand rather than leaf function. Results suggest that a combination of restricted root volume and development of water stress achieve the RDI response in the Goulburn Valley, Australia.

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An experiment designed to study the effects of different root volumes was installed in Fall 1991. `Golden Queen' peach trees [Prunus persica (L.) Batsch.] were planted into different isolated soil volumes (0.025, 0.06, 0.15, 0.4, and 1.0 m3), which were essentially individual drainage lysimeters. Trunk cross-sectional area (TCA) increased from 5.76 to 14.23 cm2 for the smallest and largest volumes, respectively, while leaf area was 4.56 and 21.32 m2 for the respective treatments. Leaf size was not affected by soil volume. Soil volume was positively related to the number of lateral shoots produced, lateral shoot density, and internode length. Total flower bud number and flower bud density were inversely related to soil volume. Fruit set was similar among treatments despite an almost 4-fold difference in tree size. Tree water use (liters·mm-1 pan evaporation) increased with soil volume; however, when adjusted for tree size (tree water use per TCA), there were no consistent differences between treatments for tree water use over the season. These results suggest that trees planted in the smaller soil volumes were more efficient reproductively per unit of tree size and would be easier to manage in an ultra-high-density planting.

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