Studies On And Biological And Morphological Characteristics Of Paeonia×Suffruticosa Zhongyuan Group

Studies on biological characteristics and cultivar resources are important both for basic research and for cultural practice of tree peonies. At present, there are totally 17 cultivar groups of tree peonies developed around the world, among which Paeonia Xsuffruticosa Zhongyuan Group is typical of traditional Chinese tree peony cultivars most extensively cultivated in the world. The phenophase characteristics, growth and development rhythm, horticultural characters of cultivars in the Zhongyuan Group were studied in this paper and the results were summarized as follows:1. The phenophase characteristics of the cultivars of the Zhongyuan Group in Luoyang national peony garden are: buds expanded in early February to early March; buds sprouted in middle February to middle March; leaves emerged in late February to middle March; leaves unfolded in early to late March; leaflets extended in middle March to early April; bell-like flower started in late March to early April; petal color appeared in early to middle April; flower bloomed in early to late April; flower bud differentiation started in middle June and finished in morphology until middle October; leaves became yellow in early September to early November, then entered into hibernation. Therefore, the annual growth cycle of tree peonies can be divided into 11 phenophases, bud expanding, bud sprouting, leaf emerging, leaf unfolding, leaflet extending, bell-like flower, color appearance, flowering, bud growth and differentiation, foliage senescence, plant dormancy. The variable amplitude of the date of the same phenophase among various cultivars was large from bud expending to leaflets extending, then became smaller gradually until the late flowering stage, but larger when leaves became yellow.2. During the process of growth and development, annual shoots, compound leaves and flower buds got through four stages, slow growth, rapid growth, slow growth, stopped growth. And they were being rapid growth stages from leaf unfolding to bell-like flower. The growth and development are closely related to air temperature, the fluctuation of which became smaller and temperature gradually increased from the leaf unfolding, so that the effective accumulative temperature was accumulated more rapidly, and the speed of growth and development was accelerated.3. The characteristics of bud differentiation in the Zhongyuan Group are:the bract primordia started to be differentiated on June 25th, the calyx primordia on August 9th, the petal primordia on August 24th, and the stamen and pistil primordia on October 19th. When the plant entered the dormancy, all elements of a flower structure had finished their morphological differentiation while stamen and pistil primordia became petaloids in some cultivars.4. The flower bud differentiation was specialized with the different flower forms of cultivars. In Single, Lotus and Chrysanthemum forms, the petals in a flower are natural hyperplasia with normally developed stamens and pistils, but in Rose, Anemone, Crown and Hydrangea forms, the petals are partly from natural hyperplasia and most of them are from the petaloids of stamens or pistils. In Proliferation form, the top flower is formed in such two ways that the pistil primordia are proliferated and petaloid and that petal, stamen, pistil primordia are differentiated inside of the pistils of the low flower.5. In the cultivars of the Zhongyuan Group, red, purple and white are the primary flower colors, which could be divided into white, red, red-purple, purple, black and double-color. In addition, red, red-purple and purple could be further divided into two color groups respectively according to the degree of the color. Pure yellow, orange, blue and black colors are lacked in the Group.6. The cultivars of the Zhongyuan Group bloomed mainly in the mid-April in Luoyang, however, from the earliest opening on April 10th to the latest fading on May 10th, flowering in the population of the Group lasted totally one month. As for the flowering time of a single flower, it was generally 5-6d, the longest 9d and the shortest was 2d. Relatively, flowering lasted longer time in the cultivar of the Chrysanthemum form than other forms. As for a single plant or a bush, flowering covered 7-8d in common, the longest 20d and the shortest 4d.7. The evaluation on the basis of distinct application purposes showed that, among the cultivars of the Zhongyuan Group,42 cultivars including 'Dou kou nian hua','Mang ling chun se','Ying ri hong', 'Hong xia zheng hui' etc. are good for using in landscape,24 cultivars such as 'Man jiang hong','Zi feng chao yang' and 'Lan bao shi' etc. are excellent for producing potted plants, and 6 cultivars like'Hong xia zheng hui','Dou kou nian hua' and 'Luo yang hong' with an annual shoot length over 30cm are suitable for cut-flower production.