Methods of Propagating Bonsai Trees
Propagating bonsai trees is an important and rewarding technique for bonsai growers like you and me, as it allows us to produce more trees for our collection while enjoying making bonsai trees from scratch.
Bonsai propagation can be done through a variety of methods but the following four methods are the most popular ones.
- Seed propagation
- Cutting propagation
- Air layering propagation
- Grafting propagation
Each method has its own advantages and disadvantages, and the choice of method will depend on the type of tree, how fast you want to complete the process and your skill level as a bonsai grower. In my experience, some methods are easier and less complicated than others.
Seed germination is a method of propagating bonsai trees from germinating seeds, then caring for the seedlings until they are mature enough to be trained into bonsai trees. It is a simple and straightforward process but can be quite lengthy.
First, you collect seeds from a mature tree in the fall and store them in a cool and dry place. Before sowing, you need to go through a process called stratification to break dormancy in seeds most of the time. Not all seedlings that germinated are fit for making bonsai and it would take at least 5 years before they can be decent bonsai trees.
In my experience, seed germination can be challenging in the sense that it requires a lot of patience and care to make sure that the seedlings grow and develop properly as bonsai trees. You also need some experience in making a non-bonsai tree into bonsai by pruning and wiring to do this.
Pros and cons of bonsai seedlings
The pros of growing bonsai trees from seed include:
- You can start new bonsai trees in large amounts;
- You can style the tree from scratch perfectly to your liking; and
- It is a good way for growing mini bonsai.
There are some disadvantages to growing bonsai from seeds, which are;
- You do not know if the seeds are from good bonsai trees;
- Seedlings will not be identical to the parent tree; and
- Seeds from some species are difficult to germinate.
For more detailed information about the pros and cons of growing bonsai from seed, please check this post on this site.
Cutting propagation is a method of propagating bonsai trees by taking a piece of leaf, stem or roots from a healthy and established parent tree, encouraging it to develop roots, and then training it into a bonsai tree.
First, take a cutting from a healthy and mature tree in spring. The cutting should have at least one node, preferably several if you do stem cutting. Remove the lower leaves and cut the remaining leaves in half to reduce water loss. Plant it in a pot filled with well-draining soil.
If successful, they would take root after a few weeks.
It is a fairly easy process and best suited when you have several bonsai trees from which you can harvest cuttings. After all, you need to prune your bonsai trees during the course of the growing season and you can use what’s cut off from the trees for propagation!
In my experience, cutting propagation is a simple method that requires minimal tools/ materials and costs you nothing.
Pros and cons of bonsai cutting propagation
Some of the reasons you should grow your bonsai from cuttings are;
- New trees are clones of the parent tree;
- You can avoid the difficulties of germinating seeds;
- New trees mature faster than usual;
- Roots grow horizontally not vertically; and
- It is a simple process.
The negative sides of growing bonsai from cuttings are;
- It may be difficult to have enough cuttings;
- The process is not for all tree species;
- Only younger trees can be used as a source;
- There is a risk of uneven rooting; and
- New trees can be dead from diseases and pests at once.
For more detailed information about the pros and cons of growing bonsai from cuttings, please check this post on this site.
Air layering propagation
Air layering is a method of propagating bonsai trees that can be quite successful, although it is slightly more complicated than seed and cutting propagation.
Air layering involves creating a wound on a healthy and established branch or trunk, then wrapping the wound with a rooting medium (sphagnum moss or soil) and enclosing it in a protective covering (a plastic bag will do).
The branch or trunk will then develop roots at the wounded site, and once the roots have formed, they can be removed and planted as a new tree.
In my experience, air layering can be a bit trickier than seed or cutting propagation but it is still a reliable and effective method.
Conditions for air layering
There are several conditions that should be met for successful air layering, which are the following.
- The temperature should be between 60° to 77°F (15° to 25°C);
- Tree sap is flowing and tree activity is vigorous;
- Water should be present around the wound;
- Oxygen should be present for new roots; and,
- No sunlight penetrating the rooting site.
For conditions 1 and 2, choose an appropriate season (April to June). For conditions 3 and 4, you can cover the wound with sphagnum moss or soil. Condition 5 can be solved by covering the wound with a black plastic bag.
Trees that are several years old are more likely to be successful in the air layering method as branches/trunks with healthy young tissue can take root easily. But you can use old and already established trunks if the tree species are suitable for cutting propagation. If they take root by cuttings, they do by air layering.
Pros and cons of bonsai air layering
The advantages of bonsai air layering are as follows.
- You can improve the shape of the bonsai by removing the part you don’t want, leaving only the part you want;
- The process is fairly simple and you don’t need any special techniques, tools or materials;
- Bonsai air layering is less likely to fail than cutting propagation because water and nutrients are supplied from the roots of the parent tree before separating from it; and,
- You can make a bonsai in a short period of time as the part you are taking is fairly complete as bonsai.
There are some drawbacks of bonsai air layering, which are:
- The thicker and older branch/trunk is relatively difficult for rooting;
- Not all species are good for this propagation method;
- The tree may die if you use an old and/or weakened tree;
- The new tree does not have good surface roots (yet); and,
- It may look unnatural since some part of the tree is artificially and forcibly removed.
Grafting is a process of propagating bonsai trees that can be a bit complicated and requires some kind of skill. It involves joining a cutting from a desired tree onto a rootstock from a different or the same tree. The two parts are then bound together until they fuse and form a single tree.
Types of bonsai graft
There are several types of grafts that are commonly used in bonsai propagation.
- Bark graft
- Clef graft
- Approach graft
- Side-veneer graft
- Root graft
Bark graft is a method of grafting where a small section of a tree containing a few buds is removed from the scion (young shoot) and inserted into an opening in the bark of the rootstock, allowing the buds to fuse and grow into the rootstock.
Cleft graft is a method where a split is made in a branch or trunk of the rootstock, and a scion (young shoot) is inserted in the cleft.
Both cleft and bark grafts can be used to take advantage of a stronger tree species as a rootstock that is fused with a weaker species. Thanks to the rootstock that provides a strong and vigorous root system, the scion (the upper part of the tree that is fused) provides desirable traits such as foliage, flowers, or fruit.
Also, the tree can grow more quickly and develop better resistance to environmental stress when fused onto a stronger rootstock.
Approach graft is a method of fusing a branch or small tree onto a branch or trunk with the roots still attached. A branch can be fused to a different tree or the same tree. The success rate is higher than bark and clef grafts because the scions still have roots.
Approach graft is commonly used in bonsai to create a new branch where needed or to replace a dead or weak branch with a strong one.
When used as bonsai grafting, the side-veneer graft is a method of using buds or small shoots to fuse into rootstock instead of spliced branches. The buds/small shoots are cut with a small amount of woody part and then inserted into the rootstock whose bark has been scraped off with a knife.
A side-veneer graft is a great option for coniferous bonsai trees because it allows for the introduction of new buds to a specific area of the tree where they are needed, without relying on the tree’s own ability to regenerate new growth. Many conifers are slow growing and some of them are very difficult to back bud.
Root graft is a method of fusing scion roots to the roots of the rootstock. In bonsai, it is used to improve surface roots (Nebari) so that they spread evenly in every direction.
Pros and cons of bonsai grafting
- Graft propagation is useful for species that are difficult to germinate or root from cuttings, slow growing, and/or can produce only weak roots;
- You can create a large and good-shaped tree in a short period of time by joining trees with beautiful leaves and bark feature with good surface roots and Tachiagari; and,
- Flowering bonsai blooms earlier than usual, within 2 to 3 years after grafting.
- Grafting can result in a conspicuous joint, which may affect the aesthetics of the bonsai tree; and,
- Grafting can be a more complicated and labor-intensive propagation method compared to seed and cutting propagation.
Tree species best suited for bonsai propagation
Seed propagation is generally suitable for a wide range of tree species including Japanese maple but it may not be the best method for some bonsai species that are slow growing. For instance, some pine trees like Japanese black and red pines can be challenging to propagate from seed because they grow really slowly.
Cutting propagation is often used for deciduous trees that have the ability to produce roots from their shoots and stems. Some of the coniferous trees such as Shimpaku juniper, Hinoki cypress, and Japanese cedar can be propagated by cutting as well.
Other examples that can be propagated by cutting include:
- Japanese maple
- Chinese elm
- Wild rose
Air layering propagation
While some are not suited, air layering propagation is useful for a wide variety of tree species. Examples of bonsai tree species that can be propagated through air layering include:
- Japanese maple
- Chinese elm
- Japanese cedar
- Hinoki cypress
- Japanese white pine
- Shimpaku juniper
- Satsuki azalea
Depending on the type of tree and timing, new roots can emerge as early as 20 days after harvesting.
Graft propagation is generally suitable for a wide range of tree species including deciduous and coniferous trees.
Some conifer species, such as Japanese white pines can be difficult to root from cuttings but if you graft it onto a hardy rootstock such as Japanese black pines, their survival rate as a whole tree will increase.