Detailed Guide to Chestnut Grafting Propagation Methods (Part 1)
Grafting Methods for Chestnut Grafting Propagation (Part 1)
There are many grafting methods for chestnut nursery stock, mainly the following:
1. Cleft grafting
Used before bud break, when neither the scion nor the rootstock slips bark. The rootstock diameter is best at 1 cm to 2 cm. Cut the lower part of the wax-sealed scion into a long wedge shape, with both cut faces of equal length, about 4 cm. Make one side of the cut face slightly thicker and the other slightly thinner. Begin the cut 0.5 cm from the lower bud to avoid damaging it. Hold the prepared lower part of the scion in your mouth to reduce oxidation of the cut surface. Then cut off the rootstock 5 cm to 10 cm above the ground, choose the flat, straight side, and use a grafting knife to make a vertical cleft about 5 cm long at the center of the cut surface. Insert the scion into the cleft with the thick side facing outward and the thin side facing inward, making sure the cambium of the thick side aligns with the cambium of the rootstock. The upper end of the scion's cut face should stand 0.3 cm above the rootstock's cut surface to encourage callus formation. Then bind the graft union tightly and securely with plastic strips (black is best) to hold the scion firmly and prevent water loss. With this method the nursery stock grows vigorously and has strong wind resistance, but the survival rate is slightly lower than with bark grafting.
2. Cut grafting
Used when neither the scion nor the rootstock slips bark, generally suitable for small rootstocks with a diameter under 1.2 cm. First cut off the rootstock at the site where grafting is needed, then use a grafting knife to make a vertical cut about 4 cm long at 1/3 of the diameter of the cut surface. Cut the scion into two faces: the long face the same length as the rootstock cleft, the short face about 1 cm long, with the scion having 2 to 3 buds. Insert the long cut face inward into the rootstock cleft so that the cambium of the scion and rootstock align on one side, and bind the graft union tightly and securely with plastic strips. This method requires stricter binding than cleft grafting, and the nursery stock has weaker wind resistance than with cleft grafting.
3. Bark grafting
Also called insert-bark grafting. Suitable for thicker rootstocks with a grafting site diameter greater than 2 cm, carried out when the rootstock buds begin to swell and the bark slips easily. First, on the branch section of the rootstock where grafting is needed, choose a smooth spot without scars, cut off the rootstock, and smooth the cut surface. Use a bamboo splinter to insert 3 cm down at the cambium where the scion is to be inserted, then pull out the bamboo splinter. Then cut the scion with a horse-ear-shaped cut face about 4 cm long, with the rear part of the cut face thick and the front part thin, until almost no xylem remains at the very front end. Insert the scion cut face inward into the intended site. Do not insert the cut face entirely into the bark layer; leave about 0.3 cm above the cut surface. Then bind the graft union tightly and securely with plastic strips. This method has a high survival rate and the nursery stock grows vigorously, but wind resistance is poor: after the new shoots from the scion grow to 30 cm, they tend to break off at the graft union in wind.
1. Cleft grafting
Used before bud break, when neither the scion nor the rootstock slips bark. The rootstock diameter is best at 1 cm to 2 cm. Cut the lower part of the wax-sealed scion into a long wedge shape, with both cut faces of equal length, about 4 cm. Make one side of the cut face slightly thicker and the other slightly thinner. Begin the cut 0.5 cm from the lower bud to avoid damaging it. Hold the prepared lower part of the scion in your mouth to reduce oxidation of the cut surface. Then cut off the rootstock 5 cm to 10 cm above the ground, choose the flat, straight side, and use a grafting knife to make a vertical cleft about 5 cm long at the center of the cut surface. Insert the scion into the cleft with the thick side facing outward and the thin side facing inward, making sure the cambium of the thick side aligns with the cambium of the rootstock. The upper end of the scion's cut face should stand 0.3 cm above the rootstock's cut surface to encourage callus formation. Then bind the graft union tightly and securely with plastic strips (black is best) to hold the scion firmly and prevent water loss. With this method the nursery stock grows vigorously and has strong wind resistance, but the survival rate is slightly lower than with bark grafting.
2. Cut grafting
Used when neither the scion nor the rootstock slips bark, generally suitable for small rootstocks with a diameter under 1.2 cm. First cut off the rootstock at the site where grafting is needed, then use a grafting knife to make a vertical cut about 4 cm long at 1/3 of the diameter of the cut surface. Cut the scion into two faces: the long face the same length as the rootstock cleft, the short face about 1 cm long, with the scion having 2 to 3 buds. Insert the long cut face inward into the rootstock cleft so that the cambium of the scion and rootstock align on one side, and bind the graft union tightly and securely with plastic strips. This method requires stricter binding than cleft grafting, and the nursery stock has weaker wind resistance than with cleft grafting.
3. Bark grafting
Also called insert-bark grafting. Suitable for thicker rootstocks with a grafting site diameter greater than 2 cm, carried out when the rootstock buds begin to swell and the bark slips easily. First, on the branch section of the rootstock where grafting is needed, choose a smooth spot without scars, cut off the rootstock, and smooth the cut surface. Use a bamboo splinter to insert 3 cm down at the cambium where the scion is to be inserted, then pull out the bamboo splinter. Then cut the scion with a horse-ear-shaped cut face about 4 cm long, with the rear part of the cut face thick and the front part thin, until almost no xylem remains at the very front end. Insert the scion cut face inward into the intended site. Do not insert the cut face entirely into the bark layer; leave about 0.3 cm above the cut surface. Then bind the graft union tightly and securely with plastic strips. This method has a high survival rate and the nursery stock grows vigorously, but wind resistance is poor: after the new shoots from the scion grow to 30 cm, they tend to break off at the graft union in wind.