A green roof system was installed on an existing 35-year-old building. The purpose of the study was to evaluate the effect of three substrate depths on low-temperature injury of six herbaceous perennials: bugleweed (Ajuga reptans), sandwort (Arenaria verna `Aurea'), sea pink (Armeria maritima), whitlow grass (Draba aizoides), creeping baby's breath (Gypsophila repens), and stonecrop (Sedum xhybridum). Plants in 4-inch (9-cm) pots were transplanted into three substrate depths: 2, 4, and 6 inches (5, 10, and 15 cm) and evaluated over a 3-year period. The analysis of the results showed that the species have different winter hardiness, therefore some species were subject to more freezing injury than others. Stonecrop had significantly more damage at 2-inch than 4- or 6-inch depths during the two winters. Bugleweed and creeping baby's breath showed more damage at 2 inches in 1996-97, not in 1995-96. Substrate temperatures were measured from Oct. 1995 to May 1997. Low temperature injury was more pronounced at 2 inch than at 4 or 6 inch depths. Minimum daily temperature and temperature variations measured in fall and spring of these 2 years were also higher at 4- and 6-inch depths.

Phalaenopsis cultivars are epiphytic orchid plants with high economic value, largely produced across the world as potted plants or cut flowers. The goal of this experiment is to show if aseptic (in vitro) Phalaenopsis plants can absorb urea with their roots. Young in vitro Phalaenopsis plants were transferred aseptically to a growth medium (solid or liquid) where the three forms of nitrogen (nitrate, ammonium and urea) are equally present and where only one form at a time is marked with 15 N. The 15 N analysis of the younger leaves of each plant shows that urea and ammonium are the two preferred forms of nitrogen absorbed, with respectively 47% and 41% of the total amount, while nitrate is only absorbed to a level of 12%. The medium analysis revealed that no urea hydrolysis occurred before root absorption. Phalaenopsis roots, probably because of the special nature of velamen, can absorb large amounts of nitrogen directly in urea form. This experiment suggests that the medium of Phalaenopsis in vitro plants could advantageously contain a large proportion of nitrogen in urea form, and that this concept could probably be applied to fertilizer solutions used in growing Phalaenopsis pot plants and other orchids species.

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. These plants were observed over a 5-yr period to validate the climatic zonal range attributed to the species and to determine the winterhardiness of the cultivars. Winter damage observed each spring indicated that Thuja occidentalis L. can survive in climatic conditions more severe than those suggested in the litterature. However, survival varies among the cultivars studied. Woodwardii, Reidii, Wareana and Lutea showed a winterhardiness similar to the species. Pulcherrima showed the most damage. Little Champion, Smaragd and Fastigiata cultivars gave a response between the two other groups. Furthermore, growth in terms of height and width of the species and each cultivar was influenced by the different climatic conditions of each location.

The growth of 10 rose cultivars of the Explorer™ Series, propagated by in vitro culture, cutting and grafting on Rosa multiflora Thunb. was studied under natural and extreme winter climatic conditions in four climatic zones in Quebec. These extreme winter conditions were created using snow removal or ice application techniques. The difference in propagation methods was observed after the first two winters for plant mortality, whereas it was most apparent for final plant height and width measurements after the third and final growing season. At the end of the trial, grafted plants of Alexander McKenzie and Frontenac were shorter, Captain Samuel Holland and John Davis were taller, Alexander McKenzie and Simon Fraser were narrower and Henry Kelsey, John Davis and Louis Jolliet were broader than the plants propagated either by cuttings or in vitro culture. There were no significant differences for plant height or width for all cultivars at all evaluation sites under natural winter conditions when either propagated using in vitro or cuttings. Under natural and extreme winter conditions, variations between climatic zones for final height and width of plants indicated that for Louis Jolliet and Simon Fraser there were no differences between zones and, furthermore, plants evaluated in zones 5a and 2b were very often higher and larger than plants in other climatic zones. For personal use only.