Grafting Japanese Maples
Before I explain grafting it is very important to understand other methods of propagation and why they cannot be used for Japanese Maples
Propagation from seed.
Acer palmatum (Japanese Maple) includes many hundreds of unique varieties with different leaf shape, color, and growth habit. Japanese maples openly pollinate, meaning that seeds from a specific variety will sprout but they will not be an exact clone of the parent tree. In fact you will often see a lot of variance from one seedling to the next. On one occasion, I sprouted seed from 'Inaba Shidare' which is a weeping, red lace-leaf variety. I was genuinely surprised by how different the seedlings were from each other. Some were green. Some were red. Some displayed normal palmate leaves. Some had leaves that were "sort of" dissected like the parent. For the most part they were a mixed bag of leaf shape and color. It was really fun but it certainly did not yield me a clone of 'Inaba Shidare'. It is frustrating that seedlings are not exact clones of the parent but at the same time it is really wonderful because that is how most new varieties are discovered. A chance seedling that looks so unique and different from any other variety that it must be given its own name.
Propagation from cuttings.
Another possible method of propagation in the world of trees is by rooted cuttings. A small branch or "cutting" is taken from the desired parent plant and inserted in soil. Over the period of several months the cutting will root if given a perfect environment. Normally that environment includes a shade house with little to no air movement and an overhead misting system. Unfortunately most varieties of Japanese Maples simply will not root, even under perfect conditions. If they do root, percentages are normally very low and often produce a tree that is very weak and eventually dies because of a weak root system. Of course there are always exceptions to the rules. Varieties like 'Bloodgood', 'Ara Kawa', and 'Kiyohime' are less difficult to root and in fact seem to do very well on their own roots.
Propagation by Grafting
Grafting is the principal method of propagating Japanese maple cultivars, both in commercial production and for the hobbyist. A small branch called the "scion" is removed from the parent tree and grafted onto another tree called the "understock". The understock is normally a seedling of a green leaf, upright growing Japanese maple. This type is chosen as understock because it generally is fast growing with a vigorous and hardy root system. The seedling is grown for 2-3 years before it is large enough to be used as understock. Typically the tree must have a trunk that is wider than 1/8 inch. In commercial production, 3/16 to 1/4 inch is used the most.
For winter grafting, the understock is brought into the warm greenhouse in January and forced out of dormancy. After 3-4 weeks, the understock is ready to be used for grafting. On the day of grafting, the scion wood is collected from the parent tree that you wish to clone. The parent tree will be either outside in the cold or in a cold house. So you will be grafting a dormant scion onto an actively growing understock. Normally a 1-2 inch vertical cut is made on the understock and then a similar cut on the scion wood. The scion wood is then grafted onto the understock. The newly grafted tree is placed on a heated bench in the greenhouse. High humidity levels must be maintained as well as very specific nighttime and daytime temperatures. Often shade is provided for the newly grafted trees to reduce daytime stress. Once the graft "takes" the scion will push out leaves and after a month, the new graft can be moved off the grafting bench.
Here at Maplestone, we take great pride in our grafting. We use a handful of different grafting techniques based on time of year and size of grafting wood. A strong and smooth graft union is always our goal.