Origin

‘Jiaoju’ was originally observed in 2004 in a long-term M. wufengensis domestication experiment in Wufeng County, Hubei Province, China. In 2005, we collected branches from the wild M. wufengensis trees and used the single-bud grafting method to propagate them in our experimental base in Xianning, Hubei Province, China. The propagation was conducted through grafting onto Magnolia biondii rootstocks. In this experiment, we grafted 200 plantlets, of which 60 survived. From 2006 to 2008, this cultivar was propagated annually using branches from the previous year’s surviving plantlets. In total, 1000 plantlets were propagated through second- and third-generation grafting, with more than 90% survival. The plantlets originated from the grafting experiment in 2005 and started flowering in 2008 with chrysanthemum-like flowers. All propagation took place in low-elevation plains in China, and this cultivar shows strong adaptation to such environments. Furthermore, all offspring exhibited the same floral characteristics as their parents, with no atavism observed.

Description and Performance

Like most other magnolia cultivars, ‘Jiaoju’ is hysteranthous, with leaves appearing after blooming. This cultivar is expected to reach a mature height of 15 to 20 m. It blooms in early spring with solitary, pink, fragrant, chrysanthemum-shaped flowers erecting at the branch tips (Fig. 1A).

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While ‘Jiaoju’ shares many traits with other M. wufengensis cultivars, it exhibits distinct characteristics in both leaves and flowers. To better describe ‘Jiaoju’, we made comparisons on key characteristics with its sibling cultivar ‘Jiaohong No. 1’ (Xiao et al. 2018). ‘Jiaoju’ has obovate leaves alternatively arranged on the branches, whereas ‘Jiaohong No. 1’ has ovate leaves. Each leaf of ‘Jiaoju’ has a cuneate base, a rounded apex, an entire margin, and clear five to eight pairs of leaf veins. The colors of abaxial and adaxial leaves are dark and light green, respectively.

The differences in floral traits are even more astonishing. Unlike most of its sibling cultivars such as ‘Jiaohong No. 1’, ‘Jiaoju’ has 12 to 24 pink, bar-shaped tepals (Fig. 1A; Table 1). The tepals of a ‘Jiaoju’ flower are also narrower with a width of 2.3 ± 0.3 cm (n = 20) and length of 6.6 ± 0.3 cm (n = 20). According to the Royal Horticulture Society (RHS) Color Charts (5th ed), the colors of abaxial and adaxial tepals are pink (RHS 62A-62C; Fig. 1B) and light pink (RHS 62C-D; Fig. 1C). The overall shape of the flowers is quite similar to a chrysanthemum flower, which provides a distinct esthetic value to this cultivar.

Table 1. Differences in flower and leaf characteristics between Magnolia wufengensis ‘Jiaoju’ and M. wufengensis ‘Jiaohong No. 1’.

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From observations of 50 ‘Jiaoju’ plants in Hubei province (US Department of Agriculture Cold Hardiness Zone 9a) for 4 consecutive years from 2020 to 2024, ‘Jiaoju’ starts blooming between mid-March to early April. Its flowering continues for 23.2 ± 0.7 d (ranging from 15 to 31 d). We recorded the time at different flowering phases. Specifically, the first flowering period lasts for 8.1 ± 0.5 d (ranging from 3 to 13 d); the full flowering period 7.4 ± 1.7 d (ranging from 5 to 10 d); the withering period 4.1 ± 0.2 d (ranging from 2 to 6 d); and the end of flowering period 8.6 ± 0.5 d (ranging from 3 to 14 d).

Dissemination of Cultivars

Currently, ‘Jiaoju’ is propagated through grafting on healthy rootstocks of M. wufengenesis, M. biondii, and M. denudata. Single-bud grafting in fall in regions with tropical and subtropical climates or spring with temperate climates is recommended. Fertile and well-drained soils with mild acidity are ideal for this cultivar.

‘Jiaoju’ can be planted in a wide range of environments. By Mar 2022, ‘Jiaoju’ has been introduced as ornamentals into five cities in Central, East, and North China, including Ningxiang (Hunan) and Dangyang (Hubei); Changzhou (Jiangsu); and Sanhe (Hebei) and Beijing. All plants have healthy growth and are capable of overwintering and oversummering in these cities.

Availability

The cultivar Jiaoju is a good choice of ornamentals, especially in low-attitude plain areas. It was developed and maintained by Beijing Forestry University (Beijing, China), Three Gorges University (Yichang, China), and Wufeng Boling Seed Industry Co., Ltd. (Yichang, China). The field-planted breeding materials for ‘Jiaoju’ are available in Wufeng Boling Seed Industry Co., Ltd. Contact the coauthor Dr. Zhonglong Zhu (e-mail: 515813518@qq.com or thefuturehero@163.com) with requests.