Grafting, purpose and best techniques

Grafting plant

Grafting, together with preparing cuttings, is one of the most important know-hows to learn when propagating trees and shrubs.

With this easy-to-follow guide, you’ll realize grafting isn’t as difficult as you thought it was? Everyone can give it a try – and succeed!

What is grafting?

Definition

Before digging into the details of grafting, it’s important that you familiarize yourself with a few key words.

  • Rootstock or stock: as the name shows, it’s the plant part that will provide the trunk and root portion of the graft. When the graft has succeeded, roots from the rootstock will provide nutrients to the scion.
  • Scion: portion of the plant (often a twig) that is to be fused with the rootstock. The goal is to reproduce the species or the cultivar it was cut off from.
  • Cambium: thin layer of plant tissue located just underneath the bark. You may observe it directly if you scratch the bark off lightly, uncovering a thin bright green, sappy layer. Cambium is where roots emerge from when preparing cuttings or marcotting. It also makes it possible for the scion to fuse with the rootstock.

At this point you’ll have understood a key fact: grafting is the art of joining two healthy plant parts into a single one.

What is grafting for?

Grafting makes it possible to multiply plants that cannot be reproduced through either seeds or cuttings. It also serves to rejuvenate a tree or shrub that might have lost its productivity (whether fruit or flower). Not only can you multiply plants: grafting also combines the advantages of both scion and rootstock. Typically, rootstock species and varieties are chosen for their vigor and resistance. As for the scion, usually beauty and fruit-bearing are the criteria for selection.

  • For example, beautiful roses are often grafted atop dogrose rootstocks;
  • cherry, on the other hand, is attached to wild cherry or to mahaleb cherry (Prunus mahaleb).
  • As a last example, an orange tree cutting is often grafted to a Poncirus trifoliata variety.

What do I need for grafting?

Grafting equipment is relatively simple, and you can find it in every garden store. This is what you’ll need:

  • a grafting knife (a knife with a curved blade). Make sure it’s sharp and disinfect it;
  • raffia;
  • wax or grafting paste.

When to graft?

The best time to perform a graft depends on the technique you’re using. In general, you’d graft in spring. Before that, though, you’ll collect or uproot the rootstock in winter, on days when it isn’t freezing. In the meantime, you’ll heel them in. This means to transplant them loosely in cool soil, ideally along the north side of a fence or wall. The goal is to extend dormancy for these so that buds remain intact until the day you’re going to graft. The technical name for this is stratification.

Factors to succeed a graft

To make sure everything happens as planned and increase the success rate for your graft, there are a few rules to follow:

  • Grafted tip of a fruit treeBoth rootstock and scion must be healthy.
  • To prevent contamination, the grafting knife should be clean and, if possible, disinfected.
  • Scion and rootstock must be compatible. Usually, it’s better to select plants that come from the same family, or at least the same botanical genus.
  • In all the grafting techniques, the key factor for the graft to “take” is to ensure that the thin layers of cambium of scion and root-stock overlap.
  • When the graft has succeeded, remove the tie that held both parts together. It’s important to remove it so that you don’t strangle new bark. If it’s too tight, it’ll start swelling above and below the tie.

What are the different grafting techniques?

Approach grafting

This type of grafting unites two specimens to one another, both being planted in the ground or in a pot. To perform an approach graft, you must:

Approach grafting steps

  • Slice off a strip of bark from both the scion and the rootstock. The space left behind once you’ve removed the strip should be the same size, and both trees must still have their cambium visible and intact.
  • Press the bared cambium together, matching up the corners and ensuring the cambium is in flush contact.
  • Use raffia to tie the joint together, and cover everything with grafting paste.

Generally, two months are necessary for this type of graft to “set”. At that stage, cut the upper portion of the initial rootstock higher up, above the graft joint. Repeat this step for the scion, this time below the graft joint. Perform this technique in July, when sap circulates a lot.

Shield budding (or T-budding)

This type of graft is most used to propagate rose trees and rose shrubs. Shield grafting is performed from July to August (eventually September). To succeed, follow the steps shown here for this type of graft:

steps to make a shield graft

On the scion stem, cut out a bud (an eye) with the surrounding bark and petiole. After that, remove the leafy portion of the leaf, leaving the petiole behind. Check that there isn’t any hard wood under the shield.

  • On the rootstock, slice the bark open with two slits, marking a “T”.
  • Lift both corners left and right, and slide the shield bud in.
  • Tie everything together with raffia; don’t use wax nor grafting paste.

If the graft succeeds, the petiole will fall off on its own in October-November. At the beginning of the next spring, you can cut away the rootstock plant above the graft point. However, if the bud turns black, dries out, and doesn’t flourish, it means the graft has failed.

Cleft graft

This technique needs to be performed at the beginning of spring, just before vegetation resumes. Just as is the case for shield grafting, cleft grafting also needs several steps:

Cleft graft with a wedge and two scions

Cut the rootstock horizontally, discard the top part and keep only the stump or stem.

  • With a sharp pruning knife (disinfected beforehand), slice the stem down to a depth of nearly 2 inches (4 to 5 cm), depending on how large the stem is.
  • Keep the slit open with a wedge.
  • Select the scions: they should be 3 to 5 inches long (8 to 12 cm) and must count 3 buds / eyes.
  • Sharpen the cutting at its base, removing a portion from opposite sides.
  • Delicately insert the scions in the rootstock slit, and make sure the cambium on both scion and rootstock align.
  • Remove the wedge and wrap the graft with raffia.
  • Spread pruning paste on portions that stayed bare.

Bark graft

This type of graft is often used to regenerate an adult tree that has stopped being productive. At the same time, it helps rejuvenate the structure of the tree by replacing its structural branches.

Bark grafting steps, in pictures

For the highest chance of succeeding, bark grafting should be performed in April-May, when the target plants are in full activity. To create this type of graft, you must:

  • Select scions that are about 4 inches long (10 cm) and each have 3 buds (or eyes).
  • Slice each scion at a slant along the base, about one inch long (2.5 cm).
  • On the rootstock, cut thin vertical lines around the cut stem, long enough to slide the scions into.
  • Delicately slip the scions in the bark. Do so slowly, so that the bark has time to peel off without ripping. Also, align the cambium layers of both scion and rootstock.
  • Last step is simply to wrap it up and apply pruning paste.

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Image credits (edits Gaspard Lorthiois):
shutterstock: @tanasieeugenandrei
CC BY-SA 2.0: Alliance of Bioversity International and CIAT