Owing to flowering beautifully and colorfully in early spring, Prunus discoidea (Yu & Li) Wei & Chang is known as the “spring cherry” in Chinese. It grows commonly in forest valleys and thickets near streams at altitudes of 200 to 1100 m (Li and Bruce 2003). It is a small tree, reaching heights of 2 to 3.5 m, and its inflorescence comprises an umbel with one to three pink blossoms, characteristics that make it ideal for a garden (Shi et al. 2013; Wang 2014). Until recently, there had been only one cultivar, P. discoidea ‘Yuanchun’, which was developed by the Nanjing Forestry University in China. In 2021, a new variety, ‘Caiyun’, which originated from a wild population of P. discoidea, was authorized by the National Forestry and Grassland Administration of China (No. 20210172). ‘Caiyun’ has the ornamental characteristics of early flowering and producing a large floral display. This cultivar represents a spectacular landscape plant because of its beautiful flowering branches, which resemble colorful clouds when the flowers are in full bloom.
Origin
In Feb 2014, an ornamental specimen of P. discoidea was discovered during individual selection at the Jiangnan branch of the Jiande Forestry Center in Hangzhou, Zhejiang Province, China. The plant specimen was observed to have elongated branchlets with pendulous apexes, and luxuriant flowers with pinkish-white petals (Fig. 1). The branches of the maternal parent plant were collected and refrigerated as scions in Nov 2014. ‘Caiyun’ was propagated by splice-grafting using a branch with viable vegetative buds during the spring (i.e., February–March) in 2015, in the Qingshanhu Garden Center, Lin’an District, Hangzhou City, Zhejiang Province, China (lat. 30°13′24″N, long. 119°30′03″E; 140 m above sea level). The rootstocks were 1-year-old or perennial seedlings of Prunus campanulata, Prunus pseudocerasus ‘Daqingye’, and Prunus serrulata. From 2016 to 2020, 115 grafted plantlets were obtained, including 15 high-grafted plants and 100 low-grafted plants, all of which showed the same genetic traits as the maternal parent tree based on subsequent observations and comparisons.
The maternal parent tree and grafted plant. (A) ‘Caiyun’ maternal parent tree in Jiande Forestry Center, Zhejiang Province, in May 2016. (B) ‘Caiyun’ full-bloom stage in Jiande Forestry Center in Feb 2014. (C) ‘Caiyun’ grafted plant in Qingshanhu Garden Center, Zhejiang Province, in Mar 2019.
Citation: HortScience 58, 3; 10.21273/HORTSCI16896-22
Description
The morphological traits of ‘Caiyun’ were compared with the original P. discoidea and P. discoidea ‘Yuanchun’ (Table 1). In Jan 2016, 90 plants (30 replicates of each of three clones—‘Caiyun’, ‘Yuanchun’, and the original P. discoidea) were planted in three blocks in Qingshanhu Garden Center using a complete random-block design. Each block contained 30 replicates of each clone, with a row spacing of 200 × 200 cm, and with seedlings of P. campanulata planted as protective rows between the blocks. All plants in the blocks had the same water and fertilizer management, twice-yearly (spring and autumn) fertilization using decomposed and fermented sheep manure (2000 g·m−2) and sesame seed cake fertilizer (300 g·m−2). Morphological traits were observed for 3 consecutive years (2016–19). Thirty plants of each variant were randomly selected in three replicates for determination of the morphological traits leaf length, leaf width, leaf length/width, stipule length, flower number per inflorescence, peduncle length, corolla diameter, and cluster shape. All colors were referenced to the Royal Horticultural Society’s (RHS) color chart (Royal Horticultural Society 2007). The data were analyzed using IBM SPSS Statistics 25 software (IBM, Armonk, NY, USA).
Comparison of the main morphological characteristics among Prunus discoidea ‘Caiyun’, P. discoidea, and P. discoidea ‘Yuanchun’ from 2016 to 2020 in Qingshanhu Garden Center, Lin’an District, Hangzhou City, Zhejiang Province, China.
Plants
The mature ‘Caiyun’ plant is a small deciduous tree, up to 3 m in height, with an open posture. The bark is grayish-white (RHS 197A), glossy, and transversely split by lenticels arranged transversely. The branchlets are brownish (RHS 59A) and sparsely hairy with moderate branching ability.
Flowers
‘Caiyun’ is a type of hysteranthous plant. The inflorescences are corymbose-racemose, with three to six individual flowers per truss (Fig. 2A). The peduncles are green and 13 to 25 mm long (21.31 ± 4.10 mm), significantly longer than those of P. discoidea (5.96 ± 0.61 mm) and ‘Yuanchun’ (5.83 ± 1.41 mm). The pedicels are green, 20 to 30 mm long, and sparsely pilose. The calyx tubes are purple-red and urceolate. The sepals are explanate, purple-red, and ovate-triangular, with a rounded or mucronate apex. The corollas are flat-plate-shaped and 2.5 to 3.5 cm in diameter. The corollas have five petals, which are ovate, two-lobed at the apex, and white with pink margins. There are 20 to 30 stamens, with red (RHS 59D) or white (RHS NN155D) filaments, and one glabrous style. ‘Caiyun’ has a charming aroma, and flowers from February to March, fruiting in May.
Morphological characteristics. (A) ‘Caiyun’ plant in Qingshanhu Garden Center, Zhejiang Province, in Mar 2019. (B) ‘Yuanchun’ flowers in Qingshanhu Garden Center in Mar 2019. (C) Prunus discoidea flowers in Qingshanhu Garden Center in Mar 2019.
Citation: HortScience 58, 3; 10.21273/HORTSCI16896-22
Leaves
The juvenile leaves of ‘Caiyun’ are pale green (RHS 145A) and densely pubescent (Fig. 3A). The adult leaves are green (RHS 143A) adaxially, light green (RHS 138B) abaxially, and sparsely pilose, with six to eight pairs of clear lateral veins. The leaves are obovate-elliptical in shape, 8.0 to 12.0 cm long and 5.0 to 6.0 cm wide, with an acuminate apex and wedge-shaped base. The double-serrated margins are acute and incised with glands. The petioles are brown (RHS 165A), sparsely pilose, and 5.0 to 9.0 mm long, with two to four disciform glands at the apex (Fig. 3B). The stipules are green (RHS 141A) and linear, with pinnatifid serration (Fig. 3C).
Morphological characteristics of the foliage. (A) ‘Caiyun’ 1-year-old branch in Zhejiang Province, in May 2016. (B) ‘Caiyun’ leaves in Zhejiang Province in May 2016. (C) ‘Caiyun’ stipules in Zhejiang Province in May 2016.
Citation: HortScience 58, 3; 10.21273/HORTSCI16896-22
Compared with ‘Yuanchun’ (Fig. 2B) and P. discoidea (Fig. 2C), there are significant differences in the leaf length, leaf width, stipule length, flower number per inflorescence, peduncle length, corolla diameter, and cluster shape (Table 1).
Cultivation Techniques and Use
‘Caiyun’ has strong environmental adaptability, preferring high, light, and airy environments, and being tolerant of drought and aridity. Splice-grafting is the most appropriate method for propagating ‘Caiyun’ in spring and autumn, using branches with viable vegetative buds as scions and 1-year-old or perennial seedlings of P. campanulata, P. pseudocerasus ‘Daqingye’, or Prunus serrulate as rootstocks. The survival rates were greater than 80%. ‘Caiyun’ is best suited to loose, fertile, and well-draining soils with slightly acidic to neutral pH. Fertilizer was applied twice a year, after the flowers had fallen and before winter, using decomposed and fermented sheep manure (2000 g·m−2) and sesame seed cake fertilizer (300 g·m−2). All plants are pruned and trimmed before budbreak or after flowering in spring, focusing on leggy, diseased, and weak branches, as well as rootstocks sprouting branches.
‘Caiyun’ can be used as a landscape tree due to its pleasant-looking and luxuriant flower branches, which resemble colorful clouds when the flowers are in full bloom, and also as an afforestation tree. It can be widely cultivated in subtropical and some warm temperate regions. In addition, it can be used for cut flowers or as a potted indoor ornamental plant.
Availability
The owners of ‘Caiyun’ are Zhejiang Academy of Forestry (Hangzhou, China) and Hangzhou Landscaping Co., Ltd (Hangzhou, China). ‘Caiyun’ is available to Qingshanhu Garden Center in Hangzhou. Contact Dr. Xin Shen (E-mail: shenxinjdy@126.com) for inquiries.
References Cited
Li CL & Bruce B. 2003. Flora of China. Volume 9: Pittosporaceae through Connaraceae. Science Press, Beijing, China.
Royal Horticultural Society 2007. Royal Horticultural Society colour chart. RHS, London, UK.
Shi S, Li JL, Sun JH, Yu J & Zhou SL. 2013 Phylogeny and classification of Prunus sensu lato (Rosaceae) J Integr Plant Biol. 55 11 1069–1079 https://doi.org/10.1111/jipb.12095
Wang XR. 2014. An illustrated monograph of cherry cultivars in China. Science Press, Beijing, China.