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Gardening

Grafting Plants

The main idea behind grafting is to simply take a variety of plant with a desirable above ground characteristics, and connect it to the roots of a variety with desirable under ground characteristics.

Grafting is a propagation technique where the living tissue of two different plants are joined, and fused together into one plant. The top part of a contributing plant can be stems, leaves, flowers, and/or fruits, this part is called the scion. The bottom part of the plant contributes the roots and support, this part is called the rootstock (or understock).

Although grafting usually refers to joining only two plants together, you can join as many as needed. Multiple grafts are commonly done with fruit trees. For instance in order to get multiple varieties of apples from one tree, or to get multiple varieties of citrus like lemons, limes, oranges, tangerines and grapefruit from just one tree. Grafting is not limited to trees, grafting vegetables and/or any other plant follows the same principle as grafting fruit trees.

Why Graft Your Plants

Besides just for the obvious fun of it, there a other reasons that grafting your plants may be useful. Some of these benefits include;

  • To Take advantage of a particular rootstocks, Some rootstocks varieties may have superior growth habits, disease and insect resistance, drought tolerance, or may even be better adapted to a particular climate than that produced naturally by an ungrafted plant. Where the scion (top) of another variety may have a desired fruit size, flavor, or even plant size etc..
  • To Optimize cross-pollination, Not all plants are self pollinating, some require pollination from another variety for good fruit set, and some plants have either male or female flowers but not both. To ensure good fruit set on the female flowers, a male plant must be growing nearby. Grafting a section of a male plant to a female plant can increase good cross pollination.
  • To Increase the growth rate of seedlings, Grafting seedling onto a more mature plant can increase the growth rate of the seedlings because the root system is already established.
  • To Perpetuate clones, Clones of some species of plants can’t be reproduced from vegetative cuttings easily, because the percentage of cuttings that successfully root is quite low. But many of them can however be grafted onto seedling rootstocks.
  • Creating new Varieties Some varieties of plants don’t actually come from seeds. Some are difficult and/or just about impossible to reproduce strictly from cuttings or other techniques.

Grafting limitations

All kinds of plants can be grafted including fruits, vegetables, trees, bushes, flowers, but not all plants can be grafted together. The only real way to tell if it can be grafted is simply to try. But generally speaking plants that are closely related graft together best, and form a good graft union.  A poor graft union usually results in plants that either grow poorly, break off or just eventually die.

Types of Grafts

Although there are many different so called types of grafts (Cleft Graft, Bark Graft, Side-Veneer Graft, Splice Graft, Whip and Tongue Graft, Saddle Graft, Bridge Graft and Inarch Graft) they all basically really come down to two types of grafting techniques, top grafting and side grafting. With top grafting the scion is matched to the new stem (plant) by placing it directly on top of the rootstock stem. In most cases the scion and understock are of exact or nearly equal size. Another type of top grafting consists of splicing the scion to the side of the stem of the new rootstock (even of different sizes). In which case several scions may be attached to a single rootstock, or stem of a rootstock. The different names (types) are just given to explain the different types of cuts used to match the two stems together.

With side grafting, a partial cut is made into the stem of the scion plant (leaving the rootstock attached),  then placing it onto the cut-off stem of the rootstock. At that point both the top (scion), and the bottom (rootstock) still have their root systems attached. Once the graft has successfully formed a good union, the root system of the scion (top) is severed from it’s original root system, leaving the scion to now live solely on the new rootstock.

Taking Care of the Graft

Both preparation, and post-graft care should be taken to insure success. It’s usually better to do the grafting in the morning or late afternoon when it’s cooler so they don’t wilt, and to avoid water stress. Also if you can, it’s best to do your grafting on cloudy days, in the shade, and/or in a cool greenhouse. You should keep the grafting area and cutting utensils as clean as you can (like cleaning off the cutting blade in-between cuts) to help prevent plant diseases from getting in the graft.

All graft cuts must be smooth and straight so they will fit and line up correctly.

It’s a good idea to practice by cutting some extra twigs of the same size as the ones you intend to graft. Once you have made the matching cuts, it’s important not to let the cuts dry out. You shouldn’t try to cut more plants than you can graft together in a few minutes in order to keep the cuts from drying out, and the plants from wilting. Although, you can wrap the cut ends in a wet towel, or place them in a cup of cool water temporary if necessary. When attaching the graft, you want to make sure the stems are lined up correctly in order to form a good union, also you’ll want to wax over the cuts to help prevent diseases. Once complete you’ll need to secure the graft, this can be done a number of ways (like wrapping, tying, clamps etc.) depending on the size, and what type of graft your doing.

After grafting, it’s best to keep the plants in a warm but shaded place, about 80-85 degrees F. Also you should try to keep them in a place with high humidity (hopefully 95% relative humidity if possible) until the grafts heal. Regular misting is helpful as well to keep humidity high (just not real wet). It will likely take about a week for the graft to heal. Once the grafts heal, set them out in direct sunlight again a little longer each day in order to slowly acclimate them to the direct sunlight again. Continue to mist them if needed to prevent wilting. Once the grafts have healed and formed a good union, and shortly after growth starts (usually about 2 to 6 weeks depending on the plants), you’ll want to remove the binding material such as string, cord or even some types of nursery tape to prevent Girdling (basically choking the plant) because they wont easily expand with the plant growth.

Richard McAvoy

Professor & Extension Specialist – Greenhouse Crops.

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