Ornamental crabapples (Malus sp.), which are shrubs or small trees in the rose family (Tang et al. 2015), have a long history of cultivation and are well-known as the “national beauty” in China (Pang 2008). The plants are popular ornamentals because of their diversity of habit, including columnar, fastigiate, upright, spreading, drooping, and weeping; various flower colors, such as white, pink, red, and purple; colorful foliage, such as yellow-green, green, gradient, red-brown, purple; and gorgeous autumn and winter fruit displays (yellow, green, orange, red, purple). They are also welcomed and frequently planted in landscaping for both their beauty, and their wide environmental adaptability and stress tolerance (Fan et al. 2019).
After many years of continuous hybridization and selection work, more and more new varieties of excellent ornamental crabapples have been introduced to the market, including ‘Zi Yan’ (He et al. 2017), ‘Chang Hui’ (Hu et al. 2018), ‘Duo Jiao’ (Zhang et al. 2019), and ‘Jingxiu Hong’ (Sha et al. 2021). The breeding trend for flowering crabapples continues to be new varieties with unusual flower shapes, double petals, and novel flower colors.
Yunjuan Yunshu is a new cultivar selected and released for its excellent double flowers and bright red and purple petals arranged as a distinctive daisy flower shape.
Origin
Yunjuan Yunshu is a novel cultivar of ornamental crabapple selected from an open pollinated seedling population from the campus of Nanjing Forestry University (Nanjing, Jiangsu, China) and the National Crabapple Germplasm Genetic Center (Yangzhou, Jiangsu, China). The ornamental crabapple research group collected ∼2000 mixed seeds of nine cultivars (Purple Prince, Indian Summer, Red Jade, Harvest Gold, Donald Wyman, Sugar Tyme, Calocapa, Malus sieboldii, Cinderella) in Fall 2011. We placed these seeds with cold stratification under moist sand at −5 to 10 °C until radicles emerged. To ensure that the Malus seeds thrived, we carried out three times of soil preparation and fertilization before sowing. Raised planting beds were prepared as follows: the soil was deep tilled in Winter 2011 before freezing (deep plowing soil depth of 30–35 cm). In Spring 2012, decomposed manure (900–1000 g·m−2) was added and the soil was then tilled a second time (deep plowing soil depth of 20–25 cm), and finally, grass and rocks were cleaned up when making the seedling bed. After the preparation, seeds were sown in Spring 2012 at the National Crabapple Germplasm Genetic Center (Yangzhou, Jiangsu, China). From 1667 seedlings in 2014, one double-flowered and daisy-shaped seedling was observed and selected for further evaluation. We named this individual plant ‘Yunjuan Yunshu’. In 2015 and 2016, the plant consistently exhibited 15 to 18 petals per flower and daisy flower shape. From 2014 through 2017, we also budded it into the popular rootstock, Malus hupehensis seedlings for 3 consecutive years. Budding technique refers to the second section (cultivation of grafted seedlings) of chapter 7 in Forestry Seedling Technology (Sun 2013). In 2016 and 2017, 50 budded plants showed the same flowering characteristics, demonstrating the phenotypic stability of ‘Yunjuan Yunshu’. The breeding and selection of ‘Yunjuan Yunshu’ took 6 years, and all budded plants retained their individual blossoming characteristics. The grafted whips grew vigorously, exhibited good adaptation to high temperatures of 37 to 40 °C in Jiangsu, and had no serious pests and diseases.
Description
The distinctive ornamental characteristics of ‘Yunjuan Yunshu’ include double petals, red and purple blossoms, and daisy-like flowers (Fig. 1-1). Kelsey is the available cultivar that most closely resembles ‘Yunjuan Yunshu’. The fruit of ‘Kelsey’ is characterized by medium-sized fruits with the predominant color of brownish [RHS-173B (Royal Horticultural Society 2007)], whereas the fruit of ‘Yunjuan Yunshu’ is characterized by smaller-sized fruits and the predominant fruit color of dark red (RHS-N34A). In addition, the leaves of ‘Kelsey’ display a weak glossiness and the leaves of ‘Yunjuan Yunshu’ have a strong glossiness (Table 1).
Characteristics of flower, fruit, and foliage of ‘Yunjuan Yunshu’ crabapple. (1) Full bloom branches. (2) The blooming stage of inflorescence in ‘Yunjuan Yunshu’: (A) large bud stage; (B) initial blossoming stage; (C) full blossoming stage; (D) front view of fading flower; and (E) back view of fading flower. (3) Annual branches and leaves. (4) Mature fruit: (F) side view of a fruit sequence; (G) front view of a fruit sequence; and (H) cross-sectional view of fruits.
Citation: HortScience 58, 5; 10.21273/HORTSCI17061-22
Characteristics of flower, fruit, and foliage of ‘Yunjuan Yunshu’ crabapple. (1) Full bloom branches. (2) The blooming stage of inflorescence in ‘Yunjuan Yunshu’: (A) large bud stage; (B) initial blossoming stage; (C) full blossoming stage; (D) front view of fading flower; and (E) back view of fading flower. (3) Annual branches and leaves. (4) Mature fruit: (F) side view of a fruit sequence; (G) front view of a fruit sequence; and (H) cross-sectional view of fruits.
Citation: HortScience 58, 5; 10.21273/HORTSCI17061-22
Characteristics of flower, fruit, and foliage of ‘Yunjuan Yunshu’ crabapple. (1) Full bloom branches. (2) The blooming stage of inflorescence in ‘Yunjuan Yunshu’: (A) large bud stage; (B) initial blossoming stage; (C) full blossoming stage; (D) front view of fading flower; and (E) back view of fading flower. (3) Annual branches and leaves. (4) Mature fruit: (F) side view of a fruit sequence; (G) front view of a fruit sequence; and (H) cross-sectional view of fruits.
Citation: HortScience 58, 5; 10.21273/HORTSCI17061-22
Phenotypic attributes of ‘Kelsey’ and ‘Yunjuan Yunshu’.
Habit.
The tree has red brown (RHS-183A) branches and an upright crown, reaching 3 m high and 1.35 m wide in 6 years.
Foliage.
The leaves are elliptical, leathery, and have fine serrated margins. They are 5.8 to 6.8 cm long, and 3.0 to 3.5 cm wide. Young leaves have a red brown (RHS-187A) color and medium intensity of anthocyanin coloration (Fig. 1-3). Mature leaf blades have a dark green (RHS-131A) color and strong glossiness of the upper side.
Flower.
The cultivar has a large quantity of flowers. Each umbel inflorescence has five flowers. Each flower has 15 to 18 undulate petals, forming a deep cup-shape. Petals are elliptical, overlapping, and have prominent venations. Flowers are large (4.0–4.5 cm in diameter) with petals pressed in a horizontal position, including four to six pistils, and a large number of stamens (typically 35) (Fig. 1-2). Flower buds are red purple (RHS-64B) in color. At anthesis, the marginal area of the inner side of the petal is red purple (RHS-71D), the middle zone of the inner side is dark pink (RHS-68B), the basal zone of the inner side of the petal is medium pink (RHS-71D), and the color of the outer side is red purple (RHS-70B). Sepals are glabrous, nonrevolute, and purplish-red (RHS-N77A). The beginning of flowering (10% open flowers) is early Apr in Jiangsu, China (long. 119°55′E, lat. 32°42′N).
Fruit.
The fruit is dark red (RHS-N34A) in color, ellipsoidal, and relatively small in size (1.4–2.0 cm in cross diameter) (Fig. 1-4) and its fruit flesh color is red (RHS-44B). The fruiting calyx is deciduous, and the fruit stalk is red brown (RHS-181A), 3.0 to 4.0 cm long.
Cultivation and Pest Management
The cultivar prefers full sun, flat land, and a good depth of loose, rich, sandy soil with good drainage. It is suitable for planting between the Yellow River and the Yangtze River Basins, China (USDA Hardiness Zones 5–9) (Agricultural Research Service, US Department of Agriculture 2012).
The plant is primarily propagated by branching and budding with rootstock of Malus hupehensis. Branch grafting usually uses the wedge grafting method and should be performed from Mar to Apr in early spring. The scions should have two to four buds on current year healthy branches, ∼10–15 cm long, 0.5–1.0 cm thick. After grafting, it is necessary to tightly wrap the grafting place with plastic film and cover the scion with a long container bag (∼20 cm). If the grafting buds are fresh after 15 d, the grafting is success. Generally, container bags can be removed after 20 d, and the plastic wrapping tapes can be dismantled after 40 d (Sun 2013).
Bud grafting usually uses the T-Budding and should be performed from August to September in early fall. Scion buds should be greater than 0.5 cm in diameter from the current year. After grafting, the plastic strips need to be tightly wound from top to bottom, only the petioles and buds are exposed to prevent buds from losing water. If the grafting buds are light green after 7 d, the budding should be good. Usually, the plastic strips can be removed in March of the following year if the buds grow healthily (Fan et al. 2019).
‘Yunjuan Yunshu’ has strong resistance to pests and diseases with a low rate of production difficulty. Damage to young tips and leaves caused by aphids, apple rust pathogen, and spider mites are rare. Trunk borers have not been observed.
Availability
‘Yunjuan Yunshu’ can be requested through Nanjing Forestry University and Yangzhou Crabapple Horticulture Limited Company (Contact person: Wangxiang Zhang; E-mail: malus2011@163.com).
References Cited
Agricultural Research Service, US Department of Agriculture 2012 USDA plant hardiness zone map Agricultural Research Service, US Department of Agriculture USA
Fan JJ, Zhang WX, Zhang DL, Zhou T, Jiang H, Wang GB & Cao FL. 2019 ‘Fenghong Nichang’ flowering crabapple HortScience. 54 7 1260 1262 https://doi.org/10.21273/HORTSCI13897-19
He JL, Ma HY, Du GD, Qing SJ, Gong GJ, Liu GC & Lu DG. 2017 Breeding of a new ornamental crabapple cultivar ‘Zi Yan’ Zhongguo Guoshu. 01 82 83 https://doi.org/10.16626/j.cnki.issn1000-8047.2017.01.024
Hu DM, Han YJ, Xu JW, Wang LH, Zhu SX & Tun XJ. 2018 A new ornamental crabapple variety ‘Chang Hui’ Yuan Yi Xue Bao. 45 S2 2811 2812 https://doi.org/10.16420/j.issn.0513-353x.2018-0403
Pang SH. 2008 The study about crabapple garden planning MA Thesis Hebei Agricultural University Baoding, Hebei, China https://doi.org/10.7666/d.y1307137
Royal Horticultural Society 2007 RHS colour chart 5th ed. Royal Horticultural Society London, UK
Sha GL, Ge HJ, Huang E, Ma RQ, Zhang CL & Sun HT. 2021 Breeding of a new ornamental crabapple variety ‘Jinxiu Hong’ Zhongguo Guoshu. 06 61 https://doi.org/10.16626/j.cnki.issn1000-8047.2021.06.013
Sun SX. 2013 Forest seedling technology Jindun Publishing Company Beijing, China
Tang F, Ding ZC, Reng J, Shi D, Liu ZJ, Jing XL & Guo R. 2015 Summary of species and varieties of Chinese flowering crabapples Anhui Nongye Kexue. 43 16 190 195 https://doi.org/10.13989/j.cnki.0517-6611.2015.16.070
Zhang LL, Mao YF, Zhang CH, Zhang DJ & Sheng X. 2019 A new ornamental crabapple variety ‘Duo Jiao’ Yuan Yi Xue Bao. 46 S2 2908 2909 https://doi.org/10.16420/j.issn.0513-353x.2019-0348
