Wednesday, October 15, 2014

A Look At Grafting

In days gone by mankind developed many creative techniques to manipulate plants into producing bigger or better crops. Grafting is one of these techniques and it was developed over many centuries.  This blog post provides general info about grafting fruit trees.  This blog post was put together with advice provided by Food Garden Group member Max K, who is a long-time experienced professional who has grafted fruit trees for most of his working life.

Grafting is done for a number of reasons:
  1. To make sure a fruit tree produces a certain variety fruit rather than trusting that a pip, after many years, will produce that fruit (and if the tree the pip came from was open-pollinated that will often not be the case) or
  2. To combine the qualities of certain root-stock (decease resistance, dwarfing etc.) with the good fruiting qualities of another variety or
  3. In case of Apple and Pear trees to improve pollination by having several varieties in close proximity or
  4. To create one tree that produces multiple varieties of a fruit
All fruit trees you buy from nurseries are grafted.

This is what you need to graft:
  • a quality grafting knife that you keep clean and sharp (see photo below)
  • a pair of good secateurs
  • grafting tape
  • a fruit tree that will be the host
  • one or more 'scions', i.e. pencil-long twigs with three or more buds of the variety that you wish to add to the host. The best opportunity for collecting scions is when a productive fruit tree of the desired variety is pruned in winter.  Scions wrapped in damp paper in a sealed plastic bag will remain viable until the end of October.
A good quality clean and sharp grafting knife
Grafting is essentially ...
All trees (in fact all plants) have a green layer immediately under the bark that contains tiny channels through which water and nutrients are taken to the leaves.  This green layer is called cambium.  Grafting is matching up the cambium layers of host and scion, so the scion can begin to use the cambium of the host tree to get its water and nutrients.

The most common grafting techniques for fruit trees are:

1. Top work grafting, also called bark grafting
In this technique scions are inserted in the cambium layer just under the bark of a branch that is much thicker than the scion.  This technique is easier to master than other ones because it requires fewer precise cuts.  Grafting tape is then used to create a tight bond between branch and scion and sealing wax is then applied to cover all freshly cut surfaces.  This is the preferred technique when adding a new variety to older trees.
Top work grafting, also called bark grafting
For top work grafting you need grafting sealant.  In Southern Tasmania Roberts and Hollander Imports and some hardware stores sell this.  After the scion has been fitted and grafting tape applied to make it a tight fit, grafting sealant is applied to all freshly cut surfaces that are exposed to the air so the wound is sealed (see photo below).
Sealing wax is applied to all fresh wood exposed to the air
2. Whip and tongue grafting
For this technique it is best if the diameter of the scion is roundabout the same as that of the host-branch it is going to be attached to.  It is used when the host tree is young and therefore does not have any thick branches that can be used for bark grafting, or, when one does not want to cut any thick branches of a more mature host.
Whip and Tongue grafting
The photo below shows a young Apple tree.  The bottom circle shows where a good fruiting variety was grafted onto root-stock, using the whip and tongue technique.  Then, recently, Max K added a Fuji scion where the middle circle is in the photo.  The top circle shows the top of the scion, which has been covered with a bit of grafting sealant.  This is only needed if the top is freshly cut.

3. Bud grafting:
In this technique a bud with a bit of wood around it is cut out of a scion and is then fitted into a branch of the host as shown in the photo below.  Apricots, Peaches and Nectarines are not usually grafted using the whip and tongue or bark techniques because of the pithy nature of the scion wood and because they tend to gum.  Bud grafting is the way to go for this fruit.
The bud is taped with sealing tape.  Good watering must follow all bud grafting because the bud with shrivel up and die if you don't.
Bud grafting: a bud (right) is fitted into a branch of the host (left)
Bud grafting is the preferred method of grafting for most commercial nurserymen because you only need one bud per graft, and so you can make three or more grafts with one scion.

Before you graft consider:

1. You need to graft within the species
You can only graft a scion successfully onto a host that is of the same species.  In other words, you can not graft a Pear onto an Apple, but you can graft an Orange onto a Lemon.

2. You need to match varieties within the species
Every variety has a different 'vigour', ie. the rate at which it grows.  If you are thinking of grafting multiple varieties onto a host, it is best to choose varieties of the same vigour, so you don't have one variety completely out-growing the other(s).  'Growth habit' (upright, spreading or normal) is also important to consider.  Combining varieties that have the same vigour and growth habit is often the best strategy. There are books that can be a major resource here.  Here is one: 'The book of Apples' (Joan Morgan and Alison Richards - Edbury Press Limited UK) describes over a thousand apple varieties, many of which are available in Australia.  It will be a great help in making a considered choice.

3. You need to graft at the right time of the year
Apply bud grafts to all types of fruit trees in the 2nd half of this month.  Good watering must follow
Apply bud grafts to all types of fruit trees in the 1st half of this month.  Good watering must follow
Apply whip and tongue grafts to Japanese and early plum varieties 2nd half of the month
Apply whip and tongue grafts to apricot and late plum varieties 1st half of the month
Apply whip and tongue grafts to Apples, Pears and Cherries
Apply whip and tongue grafts to Apples, Pears and Cherries in the early part of this month.  
Apply top work grafts to Apples, Pears, Cherries and Apricots at this time of year because sap is flowing freely and the bark is lifting

Would you like to have a go?
Grafting can be really rewarding and exciting if it works.  Some people have a talent for it and will find it easy.  Others may simply never get the hang of it.  If you like to have a go at grafting, consider that you need to develop a steady hand and an eye for the size and shape of the cuts that are required.  Persistence and learning through trial and error are very much part of learning to graft.

Here are two examples of grafts Max K applied in recent times:

A year ago Max top-grafted two Sturmer scions onto an Apple tree in Marg's food garden at Howrah (photo left).  The photo on the right shows the same branch one year later.  Near the bottom of the photo you can see the brown sealing wax on top of the main branch.  In one year the left-hand graft has grown into a healthy success with multiple branches.  The right-hand scion was the weaker one and has been cut off so it does not compete with the left-hand scion.

The photo above shows one of Max K's recent really exciting grafting exercises.  In Annie's front yard at Kettering was an Apple tree that had been neglected for many years.  Max went berserk and only left the main trunk with 6 major branches and then top-grafted 2 scions onto each branch.  It will be very interesting to see how this tree develops in coming years.

Here are some YouTube videos on the subject:
Thank you, Max K, for all your valuable information and many of the grafts shown in this blog post.  Thank you, Annie, for the photos you emailed me.  Thank you, Marg, for giving me access to your garden.

Happy grafting!

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