Introduction to Bonsai Grafting (Tsugiki) | Complete Guide to Types, Timing, and Procedures

Grafting (tsugiki) is a propagation and cultivation technique that joins a scion (honoki) from one plant to the roots of another plant (rootstock/daiki), combining the characteristics of different individuals. In the bonsai world, grafting serves far more purposes than simple propagation—filling in missing branches, establishing rare varieties, and strengthening tree vigor through selection of specific rootstocks—all use cases that make it invaluable.

Grafting may seem difficult, but once you understand the basic principles and procedures, you'll find that the success rate increases significantly when performed at the right time and with proper technique.

Purposes of Grafting in Bonsai

The main purposes of grafting in bonsai are as follows.

1. Propagation of rare varieties Rare varieties that are difficult to propagate through cuttings or seed can be grown more reliably through grafting, utilizing the vigor of the rootstock.

2. Filling in missing branches (branch grafting) For long-established bonsai lacking branches in ideal positions, grafting a scion of the same species allows you to complete the desired tree form.

3. Utilizing rootstock vigor By grafting a rare variety onto a vigorous rootstock (for example, grafting apples onto Malus spectabilis), even weak species can be grown robustly.

4. Earlier flowering and fruiting Grafted trees sometimes flower and fruit earlier than those grown from seed. This effect is particularly pronounced in ume (Japanese apricot) and wisteria.

Types of Grafting

Cleft Grafting (Kirisugi)

A method in which the trunk or branch of the rootstock is cut, and the scion is inserted into the cut surface. This is the most basic and commonly used grafting method.

• Best timing: Just before spring bud break (February–March)
• Characteristics: Highly reliable; works even when diameters don't match exactly

Bud Grafting (Mesugi)

A method in which a T-shaped incision is made in the bark of the rootstock, and a bud shield (bud scion) is inserted into that opening.

• Best timing: Summer (July–August), when bark peels easily
• Characteristics: Uses less scion material; high success rate when done correctly

Side Grafting (Harasugi)

A method in which the trunk or branch is not cut; instead, a slit is made on the side and the scion is grafted in. Ideal for filling in missing branches.

• Best timing: Around spring bud break
• Characteristics: Minimizes damage to the rootstock; ideal for filling in missing branches

Root Grafting (Nesugi)

A specialized method of grafting onto roots or the base of roots, used to add or reinforce roots.

Tools Needed

• Grafting knife: Use one with the sharpest blade possible
• Disinfecting alcohol: Sterilize the blade before and after use
• Grafting tape (vinyl tape or raffia): To secure the scion to the rootstock
• Wound dressing (grafting sealant): To prevent desiccation and infection of cut surfaces
• Plastic bag or damp cloth: For storing the scion

Practical Procedure for Cleft Grafting

Here is the procedure for cleft grafting, the most commonly used method.

Preparation

Scion selection and storage: Select the branch that will become the scion 1–2 weeks before grafting and store it in a refrigerator (32–41°F / 0–5°C), protecting it from drying. Alternatively, select and use the scion on the day of grafting. Choose 3–5 node segments of vigorous branches as your scion.

Rootstock selection: Select a healthy, vigorous rootstock that is the same species or a close relative of the scion. The closer the diameter of the rootstock matches the scion, the easier it will be to align the grafting surfaces.

Grafting Procedure

1. Cut the rootstock: Cut the rootstock cleanly with a knife at the point where you'll graft, making a quick, decisive cut. The cut surface should be horizontal or slightly angled.

1. Make a slit in the rootstock: Make a vertical slit 3/4 to 1 1/4 inches (2–3 cm) deep at the center or slightly inward from the center of the cut surface, creating a wedge-shaped opening.

1. Taper the base of the scion: Carve the lower end of the scion into a wedge shape (symmetrically on both sides or on one side), approximately 3/4 to 1 1/4 inches (2–3 cm) long. Make the cut surfaces as long and smooth as possible.

1. Insert the scion into the rootstock: Insert the wedge-shaped portion of the scion into the slit in the rootstock. It is critical to align the cambium layer (the thin green layer) of the scion with the cambium layer of the rootstock. If the cambium layers do not align, the graft will not take.

1. Secure with tape: Wrap grafting tape from bottom to top around the joined area to hold the scion firmly in place.

1. Apply wound dressing: Apply wound dressing to the cut surface at the top of the scion to prevent desiccation.

1. Aftercare: Place the graft in bright shade, avoiding direct sunlight and dryness. Loosely covering with a plastic bag is also effective for maintaining high humidity.

Confirming Graft Take

If the buds on the scion begin to grow 2–4 weeks after grafting, successful establishment is likely. Leave the tape in place for several months until the graft union is stable before removing it.

Common Causes of Failure and Solutions

Misaligned cambium layers: The most common cause of failure. Match the sizes of scion and rootstock, ensuring that at least one side of the cambium layers aligns precisely.

Desiccation failure: If the cut surface dries out, the graft will not take. Work as quickly as possible and protect with tape and wound dressing.

Infection: Infection from unsterilized tools can cause graft failure. Thoroughly disinfect the blade with alcohol after each use.

Summary

Grafting is an advanced bonsai technique, but by carefully following the basics, even beginners can experience the joy of success. Start with spring cleft grafting, build your confidence through successful grafts, and gradually explore other grafting techniques.