‘Xuan Zi’ phenotypic characteristics. (A) Semiupright growth habit. (B) Leaves with undulated leaf margins. (C) Purple (RHS 77B) flowers. (D) Budding branches.
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Crape myrtles (Lagerstroemia spp.) are important ornamental woody plants, highly valued for their diverse growth habits, prolonged midsummer flowering, and rich floral coloration (He et al. 2014; Roy et al. 2015). Crape myrtles are distributed naturally across eastern and southeastern Asia, as well as northern and southern Australia, comprising 55 species and at least 500 named cultivars (Cai et al. 2011; Qin et al. 2021). However, the common gray or gray-brown trunk of most crape myrtles limits further enhancement of their ornamental appeal. Since the 1960s, extensive breeding programs for crape myrtles have been implemented both domestically in China and abroad, concentrating primarily on enhancing disease resistance, tree architecture, flower and leaf color, and flower shape (Hu et al. 2019; Li et al. 2015; Wang et al. 2013). However, relatively little effort has been devoted to the improvement of trunk coloration traits.
As a perennial woody ornamental, the crape myrtle’s trunk color represents a crucial selection criterion, with distinctive bark coloration enhancing its market value and landscape performance significantly (Hao et al. 2025; Pooler 2006). Therefore, it is of great importance to breed new Lagerstroemia cultivars with attractive trunk colors. ‘Xuan Zi’, a hybrid new cultivar derived by crossing L. fauriei and L. indica ‘Tuscarora’, was selected and released in 2024 by the Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Memorial Sun Yat-Sen). This cultivar has gained much attention for its distinctive red trunk, enriching the availability of ornamental Lagerstroemia, and substantially enhancing its value. To date, no serious pests or diseases have been observed. The cultivar is suitable for urban landscaping applications, including park installations, civic plazas, streetscapes, and residential courtyards.
In Summer 2014, L. fauriei (tree form, ♀ seed parent; selected for superior cold hardiness, disease and pest resistance, and drought tolerance) was crossbred with L. indica ‘Tuscarora’ (tree-form cultivar, ♂ pollen parent, chosen for desirable floral morphology and vibrant blossom coloration) at Nanjing Botanical Garden, Jiangsu Province, China (lat. 32°03′N, long. 118°49′E). More than 500 cross-pollinated seeds were collected in November for dry storage. In Spring 2015, seeds were sown in a seedbed (width, 1.5 m; length, 50 m; depth, 8.0–10.0 cm). After germination, seedlings were transplanted into the field with a 20.0- × 20.0-cm spacing. In Spring 2018, an individual plant with fragrant and red-purple (RHS 77B) (Royal Horticultural Society 2015) flowers was observed and selected for further evaluation. After 2 years of softwood/hardwood cutting (2018–19) and 5 years of successive observations (2018–22), more than 100 young cuttings produced the exact morphological characteristics of the mother (donor) plant, confirming their phenotypic stability. The young trees grew vigorously and exhibited good adaptation to high (37 to 40 °C) and low (4 to 6 °C) temperatures in Jiangsu (lat. 32°03′N, long. 118°49′E; US Department of Agriculture plant hardiness zones ∼9b/10a). Throughout 5 years of breeding and field cultivation (2018–22) under natural conditions, no detectable pest or disease damage was observed. These findings occurred in the absence of artificial pathogen inoculation; rigorous resistance validation will be addressed in future studies. This cultivar was named Xuan Zi and authorized by the Forest Variety Certification Committee of China in 2024.
Among the existing Lagerstroemia germplasm, ‘Xuan Zi’ resembles ‘Ning Xiang 1’ most closely, which was released by the Nanjing Botanical Garden in 2022 (Chen et al. 2022). ‘Ning Xiang 1’ is characterized by red-purple (RHS N74C) flowers that bloom from green buds, whereas green buds and purple (RHS 77B) flowers are presented in ‘Xuan Zi’. In addition, ‘Xuan Zi’ exhibits undulating leaf margins, whereas ‘Ning Xiang 1’ does not (Supplemental Table 1). The specific characteristics of ‘Xuan Zi’ (Table 1) are described in the following sections.
The ‘Xuan Zi’ tree exhibits an arborescent form with a red (RHS 179B) trunk and branches. Its semiupright canopy can reach up to 3.0 m in height, with a 1.5-m spread at 4 years of age.
The twigs are four edged and densely covered with short wings, exhibiting low-density pubescence. The mature leaves are papery and elliptical (8.2–8.9 cm in length × 5.2–5.5 cm in width), attached by short petioles (0.5–0.6 cm). The leaf blades are green (RHS NN137A), with low-density pubescence present on the abaxial surface (Fig. 1B).
Citation: HortScience 60, 10; 10.21273/HORTSCI18778-25
The flowering time of ‘Xuan Zi’ (10% bloom opening) is relatively early, around mid June in Jiangsu, China, with a flowering period lasting over 4 months (June–September). The flower buds are green and red, cylindrical (moderate in length and width), featuring slightly raised sutures and apical protuberances. The conical inflorescence consists of numerous purple flowers (RHS 77B) measuring 2.5 to 3.0 cm in diameter, with wrinkled petals and abundant stamens (n = 25–30) (Fig. 1D). The slender, clawlike calyx connects to the petals and displays a red–purple color (RHS 73D).
The fruit of ‘Xuan Zi’ are brown, elliptical, and of medium size. Both the apex and base of the fruit lack depressions.
‘Xuan Zi’ is regenerated mainly by softwood cuttings (July–August) or hardwood cuttings (late March to early April, before sprouting). For softwood cuttings, semilignified branches should be selected and trimmed to ∼10 cm in length, retaining two to three half leaves at the apex. For hardwood cuttings, thick annual branches should be selected and cut into segments 10 to 15 cm in length, and planted at a depth of ∼8 to 13 cm. Cuttings were prepared and the basal ends were dipped in a 2000-ppm solution of indole-3-butyric acid for 5 to 10 s. The treated cuttings were then inserted immediately into the prepared seedbed. Postcutting management involved thorough irrigation, followed by covering the seedbed with plastic film to maintain humidity and temperature, complemented by shade net installation. Rooting typically occurred within 15 to 20 d. After film removal, while retaining the shade net, with proper irrigation during the growth period, new shoots can attain ∼70 cm in length within the same year.
The relevant plant material (including clonal germplasm) and research information of ‘Xuan Zi’ can be obtained from H.C. at the Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, accompanied by an official phytosanitary certification confirming compliance with China’s plant quarantine regulations (GB/T 28068-2011) and negative pathogen screening.
‘Xuan Zi’ phenotypic characteristics. (A) Semiupright growth habit. (B) Leaves with undulated leaf margins. (C) Purple (RHS 77B) flowers. (D) Budding branches.
Contributor Notes
The research was supported by the Germplasm Repository of Native Landscape Tree Species in Jiangsu Province.
H.C. is the corresponding author. E-mail: chenhong@cnbg.net.
‘Xuan Zi’ phenotypic characteristics. (A) Semiupright growth habit. (B) Leaves with undulated leaf margins. (C) Purple (RHS 77B) flowers. (D) Budding branches.
