Crabapple is a general term for some ornamental species of the genus Malus in the Rosaceae family. Under natural conditions, crabapple mostly grows in small trees or shrubs, with fruits of horticultural cultivars being less than 5 cm in diameter. China is the main genetic center of Malus and rich in ornamental crabapple resources, which has a long history of crabapple cultivation. As one of the traditional famous flowers of China, the flowers and leaves of crabapple are luxuriant and graceful, and are well known as the “national beauty” (Pang 2008). In the 18th century, some Chinese crabapple resources spread to Western countries and hybridized naturally with local Malus resources many times (Fiala 1994). Since the 1990s, breeding, cultivation, and evaluation of ornamental crabapple have been carried out in China (Guo et al. 2019). Through continuous artificial breeding and selection, more than 1200 crabapple varieties with stable characteristics and excellent ornamental performance have been selected (Zhou et al. 2018). Most varieties of crabapple have high ornamental and economic value due to their diversity of growth habits, various leaf colors, different flower shapes and colors, and various fruit shapes and colors. In addition, crabapples exhibit excellent landscape adaptability and tolerance to environmental stress such as cold, drought and poor soils, including alkaline and saline conditions. Therefore, most crabapples can be used for landscaping, gardening, tree pollination, and bonsai modeling (Guo et al. 2019).

In China, increasing numbers of new crabapple varieties with excellent ornamental performance have been introduced to the market through long-term hybridization and selection work; some of these include ‘Yun Xiangrong’ (Lu et al. 2023a), ‘Yunjuan Yunshu’ (Lu et al. 2023b), ‘Hong Xia’ (Hu et al. 2021), ‘Yanyu Jiangnan’ (Sun et al. 2023), and ‘Xijiang Yue’ (Feng et al. 2024). However, less than 10% of all known crabapple cultivars feature double or semidouble flowers (Xu et al. 2021). Here, we introduce a new semidouble flowered crabapple cultivar, Hongzi Die, which has excellent ornamental qualities and remarkable environmental adaptability.

Origin

Hongzi Die is a new cultivar of crabapple with the female parent ‘Radiant’. In Autumn 2006, 8000 seeds of ‘Radiant’ were open-pollinated with M. baccata Borkh., M. hupehensis Borkh., ‘Snowdrift’, ‘Royalty’, ‘Jiazi’, ‘Xuehua’, and ‘Xuehong’, collected from the Ornamental Crabapple Resources Evaluation Nursery of Fruit Research Base in Shenyang Agricultural University (Shenyang, Liaoning, China). After stratification in moist sand medium at 0 to 4 °C for 40 d to break dormancy, the germinated seeds were planted in nursery plates containing plug seedling substrate in Mar 2007. After 40 d of careful management, seedlings (6 to 7 leaves, ≈8 cm tall) were transplanted to the base’s nursery with a 35 cm × 50 cm spacing. In 2010, variant individual plants were observed in the flowering seedlings, among which a specific single plant with semidouble, a large number of flowers, and beautiful fruit was selected for further evaluation. After observation for 3 consecutive years (2011–14), it was found that specific traits, including flower shape and color, were stable. During Spring 2015–16, 50 asexual reproduction seedlings were propagated with the rootstock of M. hupehensis Borkh. All the grafted lines showed the same phenotypic traits, including plant habit, thorns, leaves, and flowers of the mother plant, confirming the phenotypic stability. Because the flowers of the superior line look like butterflies with red-purple color, we named it ‘Hongzi Die’ (the Chinese pinyin for butterfly is Die).

Description

The morphological traits of the cultivar Hongzi Die were compared with those of its female parent, ‘Radiant’ (Table 1), which had the same water and fertilizer management. There are some differences in flower shape, type, color, and diameter; leaf apex; fruit weight; and other characteristics between the two cultivars (Table 1). The specificity of ‘Hongzi Die’ is a semidouble flower with red-purple petals, a slight natural curl at the edges of the petals, and a spreading growth habit. ‘Hongzi Die’ has a high rate of fruiting, and the fruit is red. All colors were referenced to the Royal Horticultural Society (2015; RHS) Color Chart. The following details describe the specific properties of ‘Hongzi Die’.

Table 1. Comparisons of the main morphological characteristics between Malus ‘Radiant’ and ‘Hongzi Die’.

View Fullscreen

Habit.

As shown in Table 1 and Fig. 1A, the tree shape of ‘Hongzi Die’ is open (Fig. 1A). The surface of the trunk bark is gray and slightly smooth, and first-year branches are gray-purple (RHS-186C). It exhibits a medium growth rate and reaches a height of 5.38 m and crown width of 3.87 m at 8 years of age.

View Figure

• Download as Powerpoint
• Download Figure

Foliage.

The new expanding leaves are gray-purple (RHS-183B), and the mature leaves are ovate and dark green (RHS-139C) with a length of 9.17 to 10.48 cm and a width of 4.79 to 6.52 cm (Table 1). The mature leaves are glossy on the adaxial surface with serrated margins and an acuminate apex. The petiole length ranges from 2.83 to 3.92 cm (Fig. 1D).

Flower.

The initial bloom of ‘Hongzi Die’ occurs in mid-April in Shenyang, China. The flower is semidouble, in an umbellate inflorescence with many red-green fluffiness in the calyx and red-green flower stalks (Fig. 1E–e, a). The flower has a medium cup pattern with a narrow oval and a slightly revolute petal margin. Each inflorescence has five to seven medium-sized flowers with an average diameter of 3.41 to 3.91 cm (Fig. 1C and E–e, f). The buds are red-purple (RHS-61B), the color of the front edge, center, and back of the petal are all dark red-purple (RHS-67A), and the base color of the petal is white (RHS-NN155B) in the RHS color charts.

Fruit.

‘Hongzi Die’ bears a large numbers of fruits. The fruit is nearly round with a yellow (RHS-14D) base color and a red color (RHS-46C) on the sunny side (Fig. 1B and F). The flesh is light yellow (RHS-4D) in color and slightly sweet. Fruits are small (horizontal diameter: 1.83–2.23 cm; average single fruit weight: 5.06 g) with persistent sepals. The fruit stalk is 2.57 to 3.61 cm long (Table 1).

Cultivation

‘Hongzi Die’ demonstrates environmental adaptability and is suitable for cultivation in cold regions with minimum annual temperatures as low as −25 °C. It grows well in full sun in fertile, sandy loam with adequate moisture. The main propagation method for ‘Hongzi Die’ is bud grafting using M. baccata, M. prunifolia, and M. hupehensis as rootstocks. Scion buds were collected from healthy first-year branches and grafted onto rootstocks at least 5 mm in diameter in spring. The buds and the rootstock were bound together with plastic film to prevent water loss. The survival rates are greater than 90%. ‘Hongzi Die’ exhibits a low rate of production difficulty and is highly adaptable to cold and drought. It is also relatively free of insect and disease susceptibility.

Availability

‘Hongzi Die’ is available from Shenyang Agricultural University.