Grafting Apple Trees
Whip Graft
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| Apple harvest |
Apple trees, or Malus domestica, are deciduous trees and are among the oldest and most widely grown fruit crops in the world. The apple tree originated in Central Asia, and was one of the first tree fruits cultivated. Apple trees can now be found throughout the northern hemisphere. Today there are over 7,000 cultivars of apples. Apples can be used for cooking and making ciders as well as simply eaten. The United States is the second largest producer of apples, making their propagation important in the agricultural industry.
Apples can be propagated many ways including by seed, layering, cuttings, grafting and micropropagation. The vast majority of domesticated apple trees are grafted. Domesticated apple trees produce seeds that differ from the parent plants, which means domesticated apple trees much be vegetatively propagated, either by grafting or budding.
Grafting is commonly used in apple orchards because it can be done for propagation purposes, creating a new variety or repairing damage. For apple farmers, grafting to certain rootstocks is desirable because certain rootstocks are adapted to distinct environments, are resistant to specific diseases and can decrease the size of the tree, making the tree a more ideal height for harvesting. Another perk of grafting, you will see results more quickly than you would with cuttings and micropropagation. The advantage grafting has over budding is that grafting is done during the apple tree’s dormant months, whereas budding is done during the active growing period which is also a very busy time for farmers.
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| Apple Tree |
Many farmers graft the variety honey crisp to differing rootstocks. Since their introduction in the 1990’s, honey crisps have quickly become one of the most popular apple cultivars due to their sweet flavor. The high demand of honey crisps along with their higher market price creates an incentive for farmers to graft honey crisp scions to rootstocks of older and less popular varieties.
Whip graft and machine grafting are the most commonly uses methods of grafting today. A whip graft, also known as a splice graft, is a relatively simple grafting method. Here, I’ll go into detail on how to graft an apple tree using the whip graft.
Having the correct materials for propagation is essential. Materials needed for grafting an apple tree with a whip graft are rootstock, scion, sharp and sterile knife, budding rubber strips or grafting tape, grafting seal or wax (optional), container and media.
The first step to grafting success is selecting quality materials for your scion and rootstock. Collect your materials when the apple trees are dormant, which is during the winter months. The materials gathered need to be of current season growth. Branches must be relatively small, no bigger than 1/2 an inch in diameter. The plant used for the scion and the rootstock must be very similar in size for a successful graft.
Grafting is done during the winter or early spring in a greenhouse environment. If your plant materials are gathered prior to the actual grafting process, make sure to store the materials properly. They should be kept in cool temperatures with moist towels on the cut area to prevent desiccation. I recommend gathering your scion and preparing your rootstock at the same time you wish to complete the grafting.
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| How to cut material for whip graft |
The scion and root stock are cut with the same angle and length. Look at the figure to the left for a good visual on how the cuttings should look. The angle should be approximately 45 degrees, and the cut will be go through the entire stem. Your rootstock will be planted in a container already, so just be sure water the media well beforehand to prevent unnecessary stress for the plant. You should sterilize your knife before you do the same cut on the variety that you have selected for your scion. The most important part of this stem is to make the cuts clean without burrs and even in angle so that the scion and rootstock will fit together. Once the second cut is made, the next step is securing the scion to the rootstock.
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| Making clean cuts with a sharp and sterile knife |
The scion and rootstock are secured together with budding rubber strips, or plastic grafting tape. Make sure that you have the scion placed in the right direction with the apical side upright, otherwise the graft will not be successful. Because tying or taping the union together is an important step, it requires two people. One person is needed as the grafter, or the person who does the cutting and puts the scion in place and a second person is needed as the tier who will finish the graft by tying the union.
It is essential to make the cuts equal and even and secure the scion and rootstock tightly so that the maximum amount of cambial tissue contact is achieved. Without enough cambial tissues layers matching up between the rootstock and scion, the success rate of the graft decreases drastically. You should work rapidly to ensure the plants do not desiccate and cleanly to ensure smooth cuts that seal together nicely and provide close cambial contact.
Once the union is tied together, a grafting compound such as Doc Farwell’s Grafting Seal or grafting wax may be used for further structural support and to prevent desiccation.
Though the whip graft is most often used for grafting scion to rootstock, it can also be used to graft smaller branches onto larger ones. If this is the case, make sure the scion is placed on one side of the rootstock and not in the middles so that the cambial layers match up.
As for aftercare, keep a close eye on the graft in the first few days proceeding and keep the rootstock well watered so that plant does not become stressed. Make sure to remove the tape as soon as the graft has taken and the scion begins to grow. Failure to do so may result in girdling, which will restrict the growth of the tree. Once the scion has been growing for a few weeks, the plant can be moved from the greenhouse to an outdoor nursery environment to begin hardening off. By early summer the graft should be well established and the tree will be ready to be transplanted in an orchard.
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| http://www.geograph.org.uk/photo/227520 |
Sources
Apple Tree. 2012. http://www.2020site.org/trees/apple.html
Crasweller, R. 2005. Grafting and Propagating Fruit Trees. Penn State College of Agricultural Science Cooperative Extensions. http://pubs.cas.psu.edu/freepubs/pdfs/uj255.pdf
Hartmann, H., Kester, D., Davies, F. and R. Geneve. 1999. Plant Propagation. Pearson Education, Inc. Upper Saddle River, NJ.
Harry Ricker of Ricker Hill Orchards, Turner Maine.
Methods of Grafting. 2009. University of Minnesota Extension. http://www.extension.umn.edu/distribution/horticulture/components/DG0532c.html
Stoltz, L. and J. Strang. Reproducing Fruit Trees by Graftage: Budding and Grafting. Cooperative Extension Service University of Kentucky.http://www.ca.uky.edu/agc/pubs/ho/ho39/ho39.pdf
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