In many gardening catalogs, you can find trees that boast multiple types of fruit. This is done by grafting twigs from various trees onto a parent tree.
A man named Sam Van Aken created a tree with 40 different types of fruit growing on it. His Tree of 40 includes almonds, cherries, nectarines, peaches, and many other stone fruits, all grafted onto a single tree. Grafting is an excellent way of making the most out of a small gardening space and it can look pretty amazing. Grafting is an old technique used to join two plants together. A newer version, called budding, does the same thing, but in a different way.
How does grafting work?
The top half of a graft is called the scion and the lower portion is called the rootstock. Grafting works because plant hormones, called auxins, allow the vascular cambium tissues of both the scion and rootstock to merge. This allows water and sap to continue moving through the xylem and phloem.
Before you jump on the grafting bandwagon, however, keep in mind that grafting is tricky. It takes practice. You also need to know that, after a graft is completed, even though a protective callus has formed, and the vascular tissues have fused, the wood does not. This means that graft unions should always be considered structurally weak. You should also know that the fruit and nuts produced on grafted trees contain seeds that hold the genetic information for the scion wood only, and not that of the rootstock. Also, if you have a plant that is putting out suckers, keep in mind that these are from the root stock, and not the productive aboveground portion of your plant.
Advantages of grafting
It is pretty safe to assume that nearly all fruit and nut trees available today are grafted combinations of hardy, pest- and disease-resistant rootstock and highly productive scions.
Grafting speeds up production because young scions can be grafted onto older rootstock. This is called precocity and it allows growers to skip the 5- to 12-year juvenile phase, when trees are focusing on root system development, rather than fruit production. Grafted trees can also selected for size. Simply graft a scion from a full-sized tree onto dwarf rootstock and you get a dwarfed tree that produces more fruit. In many cases, grafting is used to imbue a tree with pest or disease resistance. This method is also used on watermelon, tomato, eggplant, cucumber, and other vegetative plants for the same reason.
Grafting for the garden
Let me say this up front - grafting requires skill. It easy to do incorrectly. There are several factors that contribute to successful grafts, and all of them are important:
Tools used in grafting
Having your tools ready ahead of time will increase your odds of successful grafting. The last thing you want is for plant tissue to dry out before you are done. [Many gardeners hold scions in their mouth as they work, to keep the plant tissue moist.] You will need sharp, sanitized pruning clippers, stretchable, biodegradable grafting tape, a sharp grafting knife, and sanitizer. You may also want to have some tree sealant or grafting wax handy.
Steps of T-budding: (a) Bud stick with short leaf stems. (b) Shield bud. (c) Inverted “T” and standard “T” cut in stock. (d) Bark opened and ready for bud. (e) Bud inserted and flaps closed. (f) Bud inserted for inverted “T” budding. (g) Rubber budding strip holding flaps and bud firmly in place. (UKY Extension)
Chip budding is similar to T-budding, except that a chip of wood is removed from the rootstock and the bud is inserted into the space.
There are several different types of grafts:
Approach grafting joins two rooted plants together to provide more support for the developing new growth. It is also used in pleaching and can be done any time of year.
Awl grafts are hard to do well as it means poking an awl under the bark of rootstock, but not beyond the cambium layer, and inserting the scion.
Bridge grafting is used in an attempt to save a tree that has been girdled by planting identical species around the injured tree and grafting them above the injury to create a nutrient bridge over the girdled portion of trunk. A similar method, called inarch grafting, uses an existing branch of the injured tree that emerges below to injury to reconnect the supply chain of nutrients.
Cleft grafting is one of the simplest and most popular forms of grafting. It takes advantages of naturally occurring clefts by inserting 3/8” scions into larger (3/4” to 2-3/4”) notches cut into Y or V-shaped joints while both plants are still dormant.
Four-flap grafts (or banana grafts) are a complex method of grafting, commonly used on pecans, in which bark from the rootstock is peeled back, like a banana, and applied to the scion.
Stub grafting is similar to cleft grafting, but the incision is made in a branch, instead of a cleft, and the scion is placed at an angle no more than 35° to the parent tree. After the scion takes, the portion of the branch above the graft is removed
In rare cases, graft hybrids, called chimera, will occur. This happens when rootstock tissues grow into the scion wood. This can lead to trees that produce flowers of both plants, plus strange combination flowers. Chimera are almost impossible to reproduce.
Whichever method you decide to use, grafting or budding, be sure to seal the area completely, either with grafting tape, tree seal, or grafting wax. This will protect against desiccation, pests, and disease, while providing some structural support, as well.
Problems associated with grafting
Grafting can provide you with added control over plants, making them more suitable to your garden theme. It can also make your foodscape healthier and more productive. But grafting requires skill and is labor intensive. Also, it is important that the proper rootstock is selected for your scions. Incompatibility may not kill the tree until several years of watering, fertilizing, and pruning have passed. Check with your local County Extension Office or rare fruit growers club for more information on compatibility before you get started.
When you first try your hand at grafting, don’t be surprised or discouraged when the alignment and pressure are insufficient, or the graft union dries out before the scion “takes” to the rootstock. This happens to beginners all the time.
If your graft works, make sure you plant your new tree at the proper planting depth. This is critical to its health and longevity. Placing graft unions below soil level invites fungal diseases, such as crown rot.
The interaction between rootstock and scion wood can be pretty amazing when it comes to plant hormones. Check out my post on photoperiodism.
Assuming you have already collected, labeled, and kept scions cool and moist, you are now ready to begin. [If not, read my post on scions first.]
Did you know that you can graft a tomato plant onto a potato plant and get food from both?
Now you know.
You can grow a surprising amount of food in your own yard. Ask me how!
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