Grafting is the primary vegetative propagation technique for ornamental crabapple, and rootstock–scion compatibility critically determines graft healing efficiency and seedling quality. Selecting suitable rootstocks is essential for the popularization of new crabapple cultivars, yet the healing performance of the newly bred cultivar Malus ‘Huabiao’ grafted onto different local Malus rootstocks remains unclear. This study evaluated graft compatibility for M. ‘Huabiao’ grafted onto three rootstocks (M. hupehensis, M. robusta, and M. baccata) through histological observation and dynamic detection of soluble sugar, soluble protein, and tannin during graft healing. The results indicated that M. ‘Huabiao’/M. hupehensis and M. ‘Huabiao’/M. robusta achieved higher survival rates (80.0% and 83.3%, respectively) and complete vascular reconstruction within 28 days, whereas the M. ‘Huabiao’/M. baccata combination exhibited a lower survival rate (63.0%) and obvious healing lag. All combinations showed consistent physiological variation trends, while the M. baccata group maintained higher soluble sugar content, greater protein fluctuations, and significantly elevated tannin levels (p < 0.05). Physiological substance accumulation was closely correlated with healing performance, with higher soluble sugar and protein levels associated with better wound recovery, and excessive tannin accumulation correlated with retarded tissue regeneration capacity. Distinct healing asynchrony was observed among combinations, with incomplete vascular connection detected in the M. baccata group at day 28. This study confirms that M. hupehensis and M. robusta are superior compatible rootstocks for M. ‘Huabiao’, and the dynamic levels of the three physiological indices can serve as potential indicators for evaluating crabapple graft compatibility.

The narrow crown, a distinct form of canopy architecture and a specialized phenotypic expression of branch angle traits in woody plants, significantly influences key physiological processes such as photosynthesis, transpiration, and biomass accumulation. This phenotype holds substantial application value in forestry production. This article aims to elucidate the biological traits and formation mechanisms of the narrow-crown phenotype in woody plants by analyzing the contributions of plant hormones, their related genes, and specific key genes to the formation and determination of branch angles. Furthermore, the review explores applications of the narrow-crown phenotype in timber forestry, orchard production, breeding of new ornamental woody varieties, and forest tree genetic improvement. Finally, we summarize recent advances in research on narrow-crowned woody plants. On this basis, the future research directions of woody plants with narrow-crown phenotype were prospected, in order to provide reference for promoting the study of branching angle formation of woody plants and the production and application of woody plants with narrow-crown phenotype.