Currently I've been experimenting with grafting stone fruit.
My experience with stone fruit has occurred because I like peaches and want to extend the range and season. As I eat many peaches each year I now have multiple seedlings which I graft.
In general, I've successfully grafted seedling peaches when they are deciduous or in February.
I use 5mm plus dormant seedlings as rootstock. The scion material included peaches apricot and plumcots. The peach scion material had the highest success rate. It appears that both the apricot and plumcot scion material need to be closer to bud burst as I had no luck with completely dormant wood. I use a basic cleft graft. Currently I use parafilm to cover the graft however this may not be necessary. For cutting small items I like to use metal backed razor blades bought from Bunnings.
If the rootstock is actively growing and the budburst window has been missed then there is the option of using a cleft graft with semihard scion in December/February.
Currently I'm experimenting with an approach graft (inarching). This technique can be used whenever the rootstock and donor scion source are actively growing. It involves exposing the cambium layer on both the rootstock and the scion source and bringing them into apposition while binding them firmly together. Ideally about 10cm of cambium is exposed. After about 6 weeks the fused scion is gradually separated from the scion source (below the junction with the rootstock). At the same time any rootstock distal to the junction should be progressively removed.
On established trees it can be useful to multigraft the tree to provide a pollinator or to have multiple fruit from the one tree. At home I've multigrafted my plumcot to increase fruit set. Immediately prior to budburst I've been able to graft the tree using a cleft graft and a bark graft. Problems which can occur when you multigraft a tree include the graft sprouting too late, for this reason it's better to multigraft varieties which have budburst at a similar time.
Bark grafting is often used if there is a large variation in diameter between the scion and host plant. It involves splitting the bark off the host thru the cambium layer. A small chisel shaped scion is then inserted before the bark is firmly reapplied with appropriate binding.
The classic cleft graft is used when the scion is similar in size to the host plant. To optimize alignment of the cambium layer on both sides you can either judge by sight or use vernier calipers to measure both the host and the scion thickness
A graft depends on the cambium layers of the scion and host being compatible and fusing. Not all stonefruit have good compatibility. Physical apposition of the cambium layer is best checked by running a finger along the join, if there's a ridge the alignment is poor. A disparity in thickness between the host and the scion can be overcome by either using an offset cut thru the host (not thru the center of the branch) this enables the width of the spit to match the diameter of the scion. Alternately the scion can be cut with a blade edge rather than a chisel point. The edge of the 'blade' is on the inside of the host while the cambium on the 'back' of the scion matches the host. The binding is then able to close the cut rather than leaving part of the cut in the host wedged open. The greater the area of contact between the cambium layers the higher the success rate. A scion should not be too big as there is a delay in establishing a link between the cambium of the host and the scion.
When you're grafting any plant it's important to ensure that moisture can't penetrate into the area of the graft. This can be achieved with good binding, paint or even silicone. Graft can also fail because the binding isn't sufficiently tight to cause good apposition between the scion and the host. Good hygiene is important, clean the tools and plant material with alcohol or diluted bleach (I use methylated spirits from Bunnings).
After care of the grafted plant is important, actively growing plants are more likely to accept a graft. The grafted plant needs to be kept in optimal condition. If they are dormant keep in a warm sunny position. If the graft is done in the warmer conditions dappled shade is ideal, it may also be necessary to protect the scion with both parafilm and a brown paper bag.
Peach grafted in July 2021
I often refer to my copy of Grafting and Budding (A Practical Guide for Fruit and Nut Plants and Ornamentals) by W J Lewis and D McE Alexander. This is an Australian publication. The internet is a good source of videos and information regarding compatibility between scions and rootstock.