Azalea

Abstract: Background Azalea (Rhododendron simsii hybrids) is the most important flowering pot plant produced in Belgium, being exported world-wide. In the breeding program, flower color is the main feature for selection, only in later stages cultivation related plant quality traits are evaluated. As a result, plants with attractive flowering are kept too long in the breeding cycle. The inheritance of flower color has been well studied; information on the heritability of cultivation related quality traits is lacking. For this purpose, QTL mapping in diverse genetic backgrounds appeared to be a must and therefore 4 mapping populations were made and analyzed.

Abstract: Planting of a shrub or tree into a mature grass sod may result in poor establishment of the woody species. This experiment was designed to measure the field response of four species of ornamental shrubs to turfgrass competition. The shrubs used were forsythia (Forsythia intermedia zabel), azalea (Rhododendron X), Japanese barberry (Berberis thunbergi DC.) and taxus (Taxus media Rend.). Turfgrass treatments included plots maintained at high or low rates of N fertilizer and receiving, in some cases, supplemental irrigation to maintain high soil moisture. Treatments with no turfgrass were either bark mulch or bare ground. Turfgrass plots were mowed regularly to a height of 7.6 cm. The effects of these variables were measured by evaluating several aspects of growth and development of each shrub species. Turfgrass established 2 years previously on an Enfield silt loam (Typic Distrochrepts) significantly suppressed the growth and development of all four species of shrubs as compared to plots where turfgrass was not a competitor. Differences in soil moisture or temperature are not believed to have been responsible for the differences observed in these findings. Plant competition for N was suggested by both the color ratings and analyses of leaf tissue of the shrubs during the first year of shrub establishment. Additional fertilizer, applied as a topdressing, was more beneficial to the turfgrass than to the shrubs, and did not significantly increase their growth in most cases. The addition of K and P did not increase growth in any of the treatments and apparently was not a factor in the competition between the grass and the shrubs.

Abstract: In the present study, long-term changes in the first bloom date of shrub and tree species in Seoul (126.56°E, 37.34°N), Korea were examined using historical observational data for the period 1922–2004 (83 years). The study focused on two shrub species, golden-bell (Forsythia koreana) and azalea (Rhododendron mucronulatum), and three tree species, cherry (Prunus yedoensis), peach (Prunus persica), and American locust (Robinia pseudoacacia). The annual-mean temperature has increased by about 2 °C in Seoul over the 83 years analyzed. The temperature increase is significant during the winter and early spring and becomes less significant during late spring. As a result of this regional warming, all five species showed an advance in the first bloom date over this time period. The advanced date is particularly apparent in early-spring flowering species like golden-bell (−2.4 days 10-year−1), azalea (−2.4 days 10-year−1), cherry (−1.4 days 10-year−1), and peach (−1.4 days 10-year−1) as compared to late-spring flowering species like American locust (−0.5 days 10-year−1). The present results have demonstrated that the major factor for the determination of flower blooming is heat accumulation, i.e. a certain threshold of growing degree-days (GDD) index. In particular, early spring flowers were sensitive to the accumulation of warm temperature than late-spring flowers. Copyright © 2006 Royal Meteorological Society