Osmanthus grafting methods and timing: choose the right rootstock for a higher survival rate

Osmanthus grafting is a commonly used asexual propagation method in osmanthus breeding. The practice involves grafting a branch or bud of an osmanthus variety onto the rootstock of another plant so that the two heal and grow into a new seedling. Compared with growing from seed, grafted seedlings can better maintain the varietal characteristics of the mother plant and flower earlier, so they are relatively widely used in propagating varieties such as Jingu Osmanthus (Golden Osmanthus), Yingu Osmanthus (Silver Osmanthus), Dangui Osmanthus (Orange Osmanthus) and Sijigui Osmanthus (Four-Season Osmanthus).

The choice of rootstock directly affects the survival rate and later growth. In production, closely related tree species such as privet (Ligustrum), small-leaf privet or fringetree (Chionanthus retusus) are mostly used. Different rootstocks each have their own characteristics; for example, fringetree as a rootstock has better cold and drought tolerance, while when privet is used as the rootstock, attention should be paid to possible later incompatibility. Grafting is mostly arranged in spring when the sap begins to flow and the buds have not yet sprouted; in areas with a suitable climate, supplementary grafting can also be done in autumn.

Commonly used grafting methods include cut grafting, cleft grafting, side grafting and approach grafting. During operation, the cambium of the scion and the rootstock must be aligned, the graft union must be tied firmly and moisture retention must be done well. For the scion, one- to two-year-old branches with pure variety and full growth should be selected; when cutting, the cut should be smooth and the action clean, so the graft union heals more easily.

Management after grafting is equally critical. During this period, the soil should be kept moist and appropriate shading should be provided, avoiding water contact at the graft union and exposure to the sun. Shoots sprouting from the rootstock should be removed in time to prevent them from competing for nutrients; after the scion survives and the new shoots grow normally, the binding material can then be gradually loosened. If the scion wilts or the graft union turns black, this is mostly related to loose binding, water loss or failure to align the cambium, and re-grafting can be done in a suitable season.