The Effects of Different Grafting Periods, Method, and Environmental Factors on the Grafting Propagation of Carpinus betulus

<i>Carpinus betulus</i> is an important ornamental landscape tree species with colorful foliage. It is widely used in landscaping due to its upright tree shape, significant seasonal changes, and good tolerance to pruning. Propagation methods for <i>C. betulus</i> include grafting, cutting, and seeding. However, the germination rate of seeding is low, and the rooting of cuttings is difficult; moreover, plant tissue culture techniques are complex, and the key technologies have not been disclosed. Grafting has therefore become the primary means of propagation. However, enabling the rapid reproduction of <i>C. betulus</i> through appropriate grafting methods and in appropriate environments remains an urgent issue to be addressed. In this study, <i>Carpinus turczaninowii</i> was used as a rootstock to graft <i>C. betulus</i>, and the effects of the grafting periods, technique, and environmental conditions on the survival rate of grafted <i>C. betulus</i> were discussed. The results showed that branch grafting (cleft graft and whip-and-tongue graft) performed in March to April and August to November resulted in the highest survival rates, whereas budding grafts (chip budding and patch budding) were more suitable in May and June. Increasing ambient humidity was a key measure for improving graft survival rates and germination rates. In terms of grafting survival rate, germination rate, and leaf growth, humidification and treatment with 60-70% light transmission had better results than treatment with natural humidity or 20-30% light transmission and full light treatment under humidification conditions. Under low-light conditions, increasing air humidity had a particularly pronounced effect on promoting the growth of grafted seedling branches. In the future, further research should be conducted on the molecular mechanism mediated by soil environment and temperature changes for the successful grafting of <i>C. betulus</i>, providing a theoretical basis for the propagation and cultivation of <i>C. betulus</i>.