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Chestnut Tree Grafting Method -
Green on Green Grafts

Ever run out of scion wood when grafting chestnut trees? Scion wood is normally obtained in the middle of the winter, January or February in the Northern Hemisphere. The scion wood is then stored refrigerated until needed in mid to late spring. Once your stash of scion wood is used up, thats the end of the grafting season. Presented here is a method of grafting chestnut trees using new scion wood with current year's growth (green growth on root stock).

So far, the green on green grafting method has only been tested using the saddle grafting method (Dirr). What makes the green on green grafting technique different is the selection of the scion wood and the root stock or under stock. The green under stock refers to current year's growth on the under stock. This new growth will have a bright green branch color.

Chestnut Root Stock

Figure #1 is a Colossal under stock with the green wood from this year's growth. The size and location of the point where the graft will be attempted is important. The under stock size needs to be near the same size as the scion wood. The material at the top of the under stock is Parafilm. Parafilm is used to seal the wood so moisture loss is minimized, giving the graft a better chance to take.

Above the Parafilm is plain old masking tape. The purpose of the masking tape is to prevent the sun from scorching the scion wood portion of the graft.

Figure #1 Green Chestnut Understock

The mother tree of the scion wood to be grafted to the root stock must be prepared about 2 weeks before grafting is attempted. Select a branch of new growth (green) of the right size. Pinch off the terminal growth. In about 2 weeks the branch will have developed new buds just below where the terminal growth was removed (Figure #2).

In figure #2 the bud is between the leaf growth on the right and the main stem on the left. The health of the mother tree is important when selecting scion wood. The mother tree in this figure is growing vigorously providing excellent material for a green wood graft. When the buds are at least 1/2 the diameter of the wood the bud is growing from, then the scion wood is ready for harvest.

Green Chestnut Scion Wood

Figure #2 Green chestnut scion wood with bud

Green Chestnut Scion Wood

Cut the prepared branch of scion wood from the mother tree at least 2" below the 3rd bud, making sure your cut is within the green growth (current year growth). Protect the scion wood from the sun by covering with moist paper towel. Take the scion wood to the tree where the graft will be performed (root stock). Find an upright branch of new growth (green) on the root stock near the main trunk. Cut the branch where the diameter of the branch closely matches the diameter of the scion wood. With a grafting knife, make a 2" cut down the center of the root stock branch, starting at the top of the cut and extending down the center 2". The branch should be split in to two, down the center (Figure #3 - bottom section).

Refer to Figure #3. Remove the scion wood from the paper towel. At the base of the scion wood, using the grafting knife, cut the scion wood on two opposing sides to create a thin 2' long1/16" thick flat section. Now slip this flattened section of the scion wood into the slit in the root stock branch.

Figure #3 Connecting Scion Wood

The entire graft must now be wrapped tightly with Parafilm, from about 1" below the cut in the root stock branch to the top of the scion wood (Figure #4). This covering is to help reduce moisture loss from the scion wood. The entire graft must now be covered with masking tape with the exception of the buds on the scion wood. The masking tape provides protection from overheating and burning the graft/scion wood.

Chestnut Bud on Scion Wood

Figure #4 Sealed Green Graft Bud

Successful Chestnut Graft

In a few weeks the graft should take and the buds should break out. At the end of the growing season the graft should like Figure #5. The picture was taken October 1, 2007 at the end of the growing season. The growing season in 2007 was colder than normal causing the new growth to be stunted. The graft would have grown much more if the growing season was warmer.

When evaluating the quality of the resulting graft look at the size of the buds and the color of the leaves. The leaves should be a deep green with color and size nearly the same as the mother tree. Before the start of the next growing season, some or most of the branches below the graft must be removed. This is to make sure the tree remains true to the new graft cultivar. Chestnut trees love to send out shoots from the root stock. Make sure suckers are removed as soon as they form.

Figure #5 Successful Graft

Dirr, Michael A., The Reference Manual of Woody Plant Propagation - From Seed to Tissue Culture

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