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  • Author or Editor: Isabelle Duchesne x
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To examine injuries caused by freezing temperatures, three woody plants were placed under temperatures ranging from 0 to –20C. Control plants were placed at 0 or –2 C, depending on the field sampling period. Freezing tests were done three times during the fall: Sept., Oct. and Nov., 1993. Spiraea × bumalda `Flamingmount', Spiraea callosa `Alba', and Spiraea × bumalda `Crispa' were tested. After freezing tests were complete, all plants were stored at –2C for the remainder of winter. In May, plants were repotted into containers. Effects of freezing temperatures on plant growth were recorded at the end of the summer. Results indicated that the most sensitive species to cold temperatures is Spiraea × bumalda `Crispa'. Moreover, the response of plants to the September freezing test was too variable to give a valid statistical analysis. Regression analysis was used as a tool to determine the temperature at which there is a 25% reduction in growth of the stem and the root dry matter, respectively. Results obtained in October are as follows: Spiraea × bumalda `Crispa', –6 and –7.6C; Spiraea × bumalda `Flamingmount', –10 and –8.7C; and Spiraea callosa `Alba' –10.7 and –11.5C. Results obtained in November are as follows: Spiraea × bumalda `Crispa', –7.1 and –8C; Spiraea × bumalda `Flamingmount', –12.2 and –12.3C; and Spiraea callosa `Alba', –8.5 and –8.7C. The reduction in cold hardiness observed for Spiraea callosa `Alba' is caused by warmer conditions (20C) in which plants were placed 2 days before the freezing test.

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To examine injuries caused by freezing temperature, six woody plants were placed under temperatures ranging from 0 to 20C. Control plants were placed at 0 or –2C, depending on the field sampling period. Freezing tests were done three times (September, October, and November) during the fall. In 1992, six species were tested: Genista tinctoria `Lydia', Parthenocissus `Veitchii', Weigela × florida `Variegata', Spiraea japonica `Shirobana', Spiraea japonica `Coccinea', and Arctostaphylos uva-ursi. After testing, all plants were stored at –2C for the remainder of the winter. The following May, plants were repotted into containers. Effects of freezing temperatures on plant growth were recorded at the end of the following summer. Preliminary results indicate that the most sensitive species to cold temperatures were Parthenocissus `Veitchii' and Arctostaphylos uvaursi. Plants of these two species did not survive the summer. However, for the third sampling period, Parthenocissus `Veitchii' (–18C) had better cold hardiness than A. uva-ursi (–9.5C). Genista tinctoria `Lydia' appeared to have the same cold hardiness (–10C) for the three sampling periods. The last three species had shown increasing cold hardiness beginning at around –8C in September to about –18C in November.

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The main objective of this research was to determine the propagation potential of Juniperus scopulorum `Wichita Blue' through grafted cuttings while using Juniperus chinensis `Hetzii' and Juniperus Sabina `Blue Danube' as a rootstock. The experiment took place in a glass greenhouse, the propagation material was either placed under a polyethylene film or intermittent mist. In each of these growth conditions the graft union was either wax coated or buried in a humid substrate. Grafting method was a side veneer graft. Each treatment was repeated three times and the experimental unit was made up of ten specimens.

Best results were obtained from the experimental trial covering the period of february to may (12 weeks). During this trial period we observed a similar rate of successful graft union whether grafted cuttings or conventional graft was used with J. S. `Blue Danube', while grafted cuttings was more successful with J. c. 'Hetzii'. Grafted cutting obtained the best results with J. S. `Blue Danube' when graft union was buried in perlite and placed under an intermittent mist. Rooting quality of rootstock cuttings was slightly inferieur to conventional cuttings for J. S. `Blue Danube' this difference was more prononced in the case of J. c. `Hetzii'

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The objective of this study was to determine the persistence and leaching of the herbicide oxadiazon in five substrates. The substrate mixtures consisted of the following: peatmoss, compost, and sand in the following proportions: 1:1:0, 3:3:2, 1:1:2, 1:1:6, and 0:0:1 in 5-liter containers. Rates of oxadiazon used were 4 and 8 kg a.i./ha on two separate split-split plots. Each experimental design had three factors: five substrates, four harvest times (24 h; 1, 2, and 3 months) and five soil depths (0–2, 2–4, 4–6, 6–8, 8– cm). Only herbicide persistence and leaching from the various substrates were investigated in this experiment; therefore, we did not remove plant material. Substrate oxadiazon residues were determined by gas chromatography analysis, and it was shown that leaching was more evident in media with a lower percentage of organic matter. In addition, oxadiazon did not leach below 4 cm in conventional substrate (1 peatmoss: 1 compost: 1 sand, respectively). The persistence of oxadiazon was affected by soil composition and herbicide persisted more in substrates with great percentage of organic matter.

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Three ornamental species (Spiraea japonica `Little Princess', Physocarpus opulifolius `Nanus', and Prunus × cistena) were potted in seven different substrates. The control substrate contained peatmoss, composted conifer bark, and fine crushed gravel (5:4:1, by volume). In the other six substrates, peatmoss was partially or completely substituted by different proportions of three organic residues (10% or 50% of the mixture made up of fresh bio-filters, 5% or 10% in composted sewage sludges, and 10% or 40% in composted deinking sludges). Four fertilization regimes (0, 200, 400, and 600 mg N/liter in the form of soluble fertilizer 20–20–20) were applied weekly onto containers. The experimental design was a split-plot with six replications. Physical and chemical analysis of the organic residues proved that the composted sewage sludges were richer in minerals than the other residues. Moreover, fresh bio-filters and composted deinking sludges were less granular than composted sewage sludges. The 10% proportion of each organic residue, combined with the other materials, was the most-adequate proportion and did not reduce the growth of plants (height, aerial and root dry matter). In addition, a dose of 400 mg·liter–1 generally gave good results, especially for fresh bio-filters and for composted sewage sludges. However, it is preferable to use a higher dose (600 mg·liter–1 if composted deinking sludges are used.

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The most widespread deformation observed in container production is root circling. Consequently, root circling often reduces growth, root regeneration, and tree anchorage at transplanting time. The objectives of this study were to test the effectiveness of Cu(OH)2 lined containers on restriction of root tips, tree growth, and potential root regeneration (PRR). Two species were used in this study: Fraxinus pennsylvanica and Acer saccharinum. Species were grown for one season in containers lined with one of six combinations of polymer (P) (0, 30, and 60 g·m–2) and copper (Cu) (0%,0.4%, and 0.8%) -coated fabric. Two other treatments were included as controls: a plastic container and a fabric container. Seedlings of each species were harvest twice: at the first season and after being transplanted from 10- to 75-liter containers. Treatments were randomized in complete blocks with six repetitions. Results of root circling length and dry weight indicate good restriction of root tips for two combinations (30 g of P/m2–0.8% Cu; 60 g of P/m2–0.8% Cu) for all species. However, treatments did not cause any reduction in stem height, trunk diameter, or stem and root dry weight. At the end of the transplanting season, PRR was greater for two combinations (30 g of P/m2–0.8% Cu; 60 g of P/m2–0.8% Cu), especially for green ash. No significant differences were observed between a plastic fabric and the two treatments cited for the other growth parameters. No phytotoxic symptoms were observed throughout the experiment.

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Effects of fall fertilization programs on cold hardiness if young Cornus alba `Argenteo-Marginata' and Weigela florida `Rumba' plants, were examined. In August 1992, four fertilization programs were applied to one year old woody plants, propagated by cuttings in 1991. Fertilization treatments were as follows: 1. discontinuation of fertigation treatments on August 30; 2. gradual decreasing nitrogen concentration (100 to 0 mg/l of 20-20-20) from August 15 to September 30; 3. constant nitrogen concentration (100 mg/l of 20-20-20) from August 15 to September 30; and 4. high potassium concentration (110 mg/l of 7-11-27) from August 15 to September 30. Whole plants were the” removed from pots and roots cleaned. They were placed under freezing temperatures ranging from 0 to -20°C at 2°C intervals. Sampling were taken at the end of September, October and November. After the freezing test, the plants were stored at -2°C. re-potted in May 1993, and evaluated for winter injury in August 1993. Results indicate that none of the four fertilization programs induced positive or negative effects on cold hardiness in both species. However, the signs of cold hardiness are observable in October at different degrees in each species. Plants of Weigela died at -12°C, while all plants of Cornus survived down to -20°C. Furthermore, a 25% loss of growth of stems and roots was found at -9°C for Weigela, while for Cornus it was -17 and -15°C stems and roots respectively.

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Slow-release fertilizers (SRF) are greatly used in container production in addition to an hebdomadal fertigation regime. For economic and environmental motives, growers wish to restrict fertigations. The objectives of this paper are to characterize the release patterns of several SRF and to determine the benefits of these fertilizers on the growth of selected woody ornamental plants. The SRF used in this study were: Osmocote®, Nutricote®, Polyon®, Nutralene® and Woodace®. The two first parts of the study were conducted in a greenhouse in Marsh 1993, with Weigela florida `Rumba' in the first part and without plant in the second one. Fertilizers were top dressed according to a medium suggested concentration. The third part of this study was done in the field in June 1993, with the same fertilizers applied in three concentrations as follow: low suggested concentration (SC), 1.5× SC and 2× SC. Two species were tested in this part, Weigela florida `Rumba' and Spiraea bumalda `Goldflame'. Growth was measured by the height of the plant, the width of canopy and the dry mass of leaves, stems and roots. Samples leachate were collected weekly or monthly for greenhouse and field studies respectively. Leachates were analysed for their mineral content per dry mass of plant tissue and the results will be presented on the poster. In the third study, plants gave a comparable growth with the first and the third fertilizer concentrations.

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Root system growth in limited volume containers can have important consequences on stem growth and root morphology. The most widespread deformation observed is root circling. Consequently, root circling often reduces growth, root regeneration and tree anchorage at transplanting time. The objective of this study is to restrict root tips. Three tree species were used in the study; Fraxinus Pennsylvanica, Acer saccharinum and Malus baccata. All species were grown in containers lined with one of six combinations of polymer (P) (0, 30 and 60 g/m2 and copper (Cu) (0, 0.4 and 0.8%) coated fabric. Two other treatments were included as controls: a plastic container and a fabric container. Treatments were randomized in complete blocks with six repetitions. Preliminary results of root circling length and dry weight indicate good restriction of root tips for two combinations (30 g of P/m2 - 0.8% Cu; 60 g of P/m2 - 0.8% Cu) for all species. However, treatments did not cause any reduction in stem height, trunk diameter or stem and root dry weight. Phytotoxic symptoms were not observed throughout the experiment.

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The objective of this study is to determine the phytotoxicity and efficiency of oxadiazon and sethoxydim used as herbicide in the production of four species of woody ornamental plants grown in containers. Four species were used: Cornus alba `Argenteo Marginata', Weigela florida `Rumba', Prunus x cistena and Thuja occidentalis `Woodwardii'. Six herbicide treatments were used (oxadiazon at 0,4 and 8 Kg (a.i.)/ha; sethoxydim at 0.000, 0.276 and 0.552 Kg (a.i.)/ha) and two controls were added (weeding and unweeding). The eight treatments were included in a complete block design replicated six times. This project was started in July 1993 and was conducted for three months. If phytotoxic symptoms were present on plants they were recorded and their effects on growth was measured. At the end of the experiment, weeds present in pots were identified, counted and their growth measured. Preliminary results showed that oxadiazon applied at rates of 4 and 8 Kg (a.i.)/ha had a good efficiency weed control in container production. Sethoxydim applied at rates of 0.276 and 0.552 Kg (a.i.)/ha had a good grass control. The two herbicides did not show phytotoxic symptoms on the for species used. The effects of herbicides on plant growth will be presented.

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