Grafting and budding is the process of joining one or more compatible cultivars together to create a single plant. This is done by forcing the two cambium layers (living cells) to heal together. In essence, budding and grafting are just two different techniques that achieve the same result- the union of a rootstock and scion. Sometimes, the two cultivars are not easily grafted together/ may be incompatible with one another. In this case, an interstem can be used to bridge the two cultivars together.
The main difference between grafting and budding is that grafting generally uses the entire branch whereas budding uses just the epithelial (skin) layer around the bud (the area from which the leaf will eventually sprout).
Much like organ grafting in humans, the two tissues join but do not exchange genetic material, and continue to have their original DNA mapping.
What is a rootstock?
A rootstock is the part of the tree that forms the root system of the grafted tree/plant. The rootstock is usually chosen to give the tree specific advantages such as cold tolerance, drought resistance, dwarfing characteristics, nematode resistance, or pest/fungal resistance. The rootstock controls the vigour and growth characteristics of the tree.
What is a scion?
The scion is the top part/cultivar of the tree and is chosen to produce the fruits/flowers. It's productivity is partially determined by the rootstock, but the taste and fruits shall be identical to that of the cultivar that the scionwood (or cutting) was taken from.
What is an interstem?
An interstem is the middle graft. It is used to help increase the compatibility (and thus graft success) between two cultivars. We can also use an interstem to dwarf a tree whilst using a vigorous, large rootstock.
When to choose to bud or graft?
Whilst both grafting and budding can be used to produce a grafted plant, the likelihood of success is dependant on the method used, the age of the tissues (older plants normally need to be grafted), the season and finally the species. Certain plants are more likely to graft together successfully if they are budded (for instance, fruit trees) whereas others do best when grafted (such as tomato plants). Budding generally causes the two cultivars to heal and join together more quickly, but can be slightly riskier because there is less energy stored in the scion and thus there is a shorter window of time where the two can join together successfully.
Why graft or bud?
Grafting and budding allows you to join two genetically similar plants together to produce a stronger plant that has chosen desirable characteristics, without having to genetically modify the plant. Fruit trees are usually grafted, as commercially viable cultivars are often intolerant to brackish soils, pests or harsh conditions. In addition, commercially farmed varieties are clones (cuttings) in any case, because consumers and stores want uniform or seedless fruit/vegetables.
Grafting has been practiced for the past 2500 years, and sometimes occurs naturally when two trees grow too close together and merge trunks. In many ways grafting/budding is similar to the tissue grafts that surgeons do- both require sterile conditions, compatibility and time for the tissues to graft together successfully. As a rule of thumb, if two varieties can successfully pollinate one another then they can be grafted together. This usually means that they need to be of the same genus and have the same diploid, haploid or triploid tendencies.
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