Before one begins clipping all sorts of plants and trees for propagation, it must be considered what plant is being propagated, and which method is going to be used. Each plant will have a window of opportunity that best suits propagation. Success rate is highly correlated to time of year that the propagation is done.
I will discuss three different methods of propagation by clipping in this article: scion bench grafting, budding or bud grafting, and direct propagation by cuttings.
Why Graft, Bud, Seed or Direct Plant | Fruit & Nut Tree Propagation
It is important to understand that plants that require cross pollination create offspring that are each unique. This is similar to humans. Seeds of an apple are going to have genetics from both the mother and the father. So, if an orchardist is interested in propagating a specific varietal of a plant that does have cross pollination, they need take a clipping! This rules out seed propagation. Grafting and budding is generally done onto ideal rootstocks that control growth and inhibit disease or onto existing trees that have a very established tree system.
Understanding a Tree | Fruit & Nut Tree Propagation
Cross Sectional Layers | Understanding a Tree
As you can see from the image below, the cambium layer is just inside the outer bark of a tree. The cambium layer is the layer of the tree that energy, nutrients and water are dispersed throughout the tree.
Parts of a Tree | Understanding a Tree
There are some terms that are generally used when talking about the tree.
Leader is the main branch(es) that are directly connected to the trunk of the tree. Common apple tree leader systems are central leader and modified central leader.
Scaffolds are the branches that come off other branches. The first set of scaffolds, called primary scaffolds, come off of the leader. Secondary scaffolds come off of the primary scaffolds.
Laterals are what come off of the secondary scaffolds and are usually where the fruiting buds grow off of. These laterals are also where the propagating wood should be taken from as it will be the youngest most vibrant of the wood.
Scion Wood is a clipping of wood taken from the laterals, ideally from last years growth wood that is most vigorous and will have the most success. When cutting for grafting, it is necessary to keep the apical (tip) and the basal (base) ends of the wood know. Some grafters will cut one end at an angle so they never have to guess at this. Others believe they can tell which end is which just by observing thickness and terminal buds.
Rootstock refers to the root section of a tree that more or less is below ground. Rootstocks are chosen for resistance to diseases, vigor of growth, and climate adaptability.
Wood Selection | Fruit & Nut Tree Propagation
Generally, the younger and fresher the wood is that’s going to be used for plant propagation, the better. When the plant is young, it has more vigor in growth and will root or graft more readily. Further, taking 1 year old whips (last year’s growth from a tree) increases chances of a successful propagation.
When taking the actual clippings, there are a few things to keep in mind.
Cutting Length | Wood Selection
The length of the cutting wood changes depending on which method one is going to be using for propagating. Generally it is considered that one or two buds will be below ground, and one or two buds will be above ground. Further, when grafting onto a root, depending on the type of tree the orchardist is propagating, one will either want one or two central leaders or an open concept based on four buds commonly found in peach trees. This means one or two buds are expected to continue on as the main leader of the tree that all other lattices will then stem off of. For budding, one only needs a branch with a lot of good buds on it. In the first year, you’re only looking for the leader growth and rooting or graft success.
When making preparations of the scion wood for grafting, the orchardist can either use a heading or a thinning cut for the scionwood depending on the source tree for the scion wood and how it is desired to train it. A inherently longer thinning cut will produce scion wood that has considerably more buds than the desired 3 for grafting. Thus, more than one scion may be cut out of the scion wood.
Cutting Width | Wood Selection
When grafting or budding the size of rootstock the scion will be grafted onto needs to be matched with the size of the scion itself. It is ideal to have the basal (bottom) end of the scion to match the exact diameter of the rootstock so that the cambium layers match up exactly.
Naturally no two plants grow the same, so even if two rootstocks have been planted at the exact same time, it is likely they will have a slightly different diameter.
This is also why a longer scion or bud wood is desired so that it can be perfectly matched when the time comes. There will likely be a little bit of wasted wood when trying to match up the diameters.
Buds | Wood Selection
There are two types of bud: leaf buds and flowering buds.
Leaf buds will offer a shoot that can turn into a scaffold.
Flowering buds turn into a flower that offers a reproductive organ.
Selecting Root Stock for Propagation | Fruit & Nut Tree Propagation
When propagating a plant, consider what size of plant is desired and what location the plant will be placed. With this in mind, a rootstock can be selected for size. Each rootstock also promises various resistances to diseases. These can be researched and debated on various sites on the web and likely the nursery’s website and staff. Generally rootstocks run in order of smallest to largest: dwarf (10 – 50% vigorous tree size), semi-dwarf (60-70%), semi-standard (or semi-vigorous)(80%), and standard (or vigorous) (100%).
Scion Bench Grafting | Fruit & Nut Tree Propagation
Bench grafting is the term given to the method of grafting that is done upon the comfortable bench of a workshop. It is often done in early Spring so that after the graft has been done, a 4 – 6 week dormancy period for healing (more on this below) is desired for the fresh graft union to heal before planting into the nursery, orchard, or garden.
Cutting the Graft Union | Bench Grafting
There are many techniques used to bench graft wood, but the most reliable and effective is the whip and tongue method, shown above. This requires a very very sharp knife. Another method is to use a tool that will cut an omega or V shape from the scion wood and rootstock that fits one into the other. Using a grafting tool is often advantageous when large amounts of grafting need to be performed.
Sealing the Graft Union | Bench Grafting
Once the grafter successfully mates up the scion with the rootstock, aligning the cambium layer, it is imperative to seal that grafting union to keep out any unwanted bacteria, viruses, water, or bugs that might harm that graft union. Remember that the union is in varying degrees of healing for ~ 2 years.
Wax has been traditionally used, but there are other mediums to use now. Some big grafters will dip the top of their newly grafted trees directly into a big pot of wax to make the process quicker.
Parafilm is a wax that stretches and can very effectively seal the graft union. I have taken the 4″ roll and cut 1 cm (1/2″) wide strips out of it. So I was left with a 4″ long 1cm wide strip. With this, you tape it like you would tape a hockey stick, and wrap it around making sure it’s forming a tight seal. The film stretches and it will break if you stretch it too long. Buds will be able to break through the parafilm, so by the end of the growing season the parafilm will start to split.
Tape options are available, as are elastics and various ties. Many of these options have the drawback that they don’t flex when the buds start to pop out or when the tree starts to grow, so you have to go around after a year and cut the tape away to prevent the tape from strangling the tree.
Dormancy Period | Bench Grafting
After the graft has been done, it is advantageous to let the graft sit in dormancy to heal for a period of about 2 months (4 – 6 weeks). This helps callus to form and heal the graft union slowly. Temperature should be from 7°C to 21°C depending on the humidity and and duration of healing period. The more humid and hotter the less time the healing period needs.
After the healing period, the root graft may be planted directly into the nursery bed.
Budding, Bud Grafting, or Topworking | Fruit & Nut Tree Propagation
There are a few different methods to budding that have various benefits and slightly different complexities. Each method has different ways that the cambium layer between the bud and the tree connect. Budding is a great technique when there is a gap or empty space in the tree’s canopy that the orchardist would like to fill in.
Budding is usually done in the middle of the growing season when the bud has exposed itself and is ready to grow vigorously. Budding is also done in the field on trees that have more or less established themselves already. This means they’re the tender first few years of growth. It is understood that the older a tree gets, the less it likes being completely chopped off and moved or topworked, like bench grafting would necessitate.
Bud Wood | Budding
Scion wood and budding wood are very similar: they each have a number of buds and are taken from 1 year old laterals. In use, the bud wood doesn’t have to be chopped into sections, each bud is removed from the bud wood and inserted into the desired section of the tree.
Sealing the Bud Union | Budding
Sealing of the bud is done in a similar fashion to the bench grafting. It is even more important to ensure that the bud can break through the seal freely. Unlike the bench graft, it is only a single bud that has been grafted onto the host tree of the new variety that will grow.
Direct Planting with Cuttings | Fruit & Nut Tree Propagation
Direct planting is done by taking a cutting from a tree and putting it into a rooting medium and allowing it to grow, first by stimulating root growth, and then by letting it shoot and start to grow upward. Instructions for the type of cutting can only be given based on the type of cutting taken. This is separated into hardwood and softwoods, where hardwoods refers to mature, dormant stems with more wood in them and softwoods refers to new, soft, succulent growth.
Rooting Medium | Direct Planting
Rooting medium refers to what the cutting will be placed in as it’s nursed into life. It typically has an organic component and a coarse mineral component of varying mixtures. It has four main functions:
- Hold the cutting in place to allow rooting to take place.
- Provide moisture for the cutting.
- Permit the exchange of air to the basal end of the cutting.
- Reduce light penetrating to the basal end of the cutting.
Sand is often used for the coarse material, but various other forms of rooting medium are available: perlite, vermiculite, expanded shale, pumice, scoria, polystyrene, rockwool..
For the organic component, peat, sphagnum moss, or barks are often used.
A rooting hormone is often used as well, which stimulates the growth of roots to form. Roots are necessary for nutrients to be taken up into the cutting to begin growing again. Auxins are one of the first hormone responses in plants that stimulates root development, and is what a rooting hormone is generally made of. Indole-3-butyric acid (IBA) or α-naphthalene acetic acid (NAA) are two common synthetic auxin, IBA being also found to occur naturally, that can be bought at most plant stores in varying potency levels identified in parts per million (ppm).
This rooting medium is then put into a pot or tray and the cutting basal end is dipped into the rooting hormone, slight tap to knock off excess hormone, and placed in the pot or tray with the basal end down.
Hardwood Propagation | Direct Planting
Hardwood stems are taken from more mature laterals in the dormant season, sometime from late fall to early spring. Hardwood refers to the wood of the clipping itself, it an older, harder growth from the tree. It can be propagated into a field, or more controlled in a greenhouse with fog, mist, or humidity control.
The cutting should be 10 – 76 cm (4 – 30 inches) in length and special care taken to identify which end is basal and which end is apical.
Rooting hormone with an IBA or NAA at 2500 – 5000 ppm should be used to ensure a root will develop, with a max of 10,000ppm for the really hard to root cuttings (which can only be known ahead of time based on species that is being propagated). One can also, with success, soak willow branches in water to extract a natural rooting hormone, but it is very hard without proper equipment to measure the potency of this and thus hard to measure an ideal application of this. However, it is a cheap and natural alternative to the synthetic approaches and purely speculative instinct tells me it will do little harm and much benefit.
Softwood Propagation | Direct Planting
Softwood refers to fresh shoots from a tree that are soft and easy to bend. These clippings are taken in the spring to early summer and ideally propagated in a greenhouse situation with controlled mist, fog, and humidity.
The cutting should be about 7.5 – 12.5 cm (3 – 5 inches). Special care needs to be taken to identify which end is basal and which end is apical.
These root easier (and thus more sensitive to transportation) than the hardwood clippings, so an IBA or NAA of 500 – 1250 ppm is ideal for the rooting hormone.
Conclusion | Fruit & Nut Tree Propagation
In conclusion, there are various methods that can be chosen to propagate a tree, and some of these methods even cross over into bushes and shrubs or tomatoes!
Care and attention must be given to the time of year the cutting is taken, and also the environment that cutting is then placed in. There are various stages of growth that happen during the propagation, which require temperature, humidity, and sunlight to be controlled. The more control one has over these variables, the more success they will have in the graft union holding. This is always a cost/benefit analysis that every orchardist must weigh.
For an orchardist, the benefit of propagating their own plants is that it is a fraction of the cost one must pay at the nursery, and far more satisfactory to see that you did it yourself. However, I have been warned numerous times that propagating plants in a nursery is a full time occupation in itself and increases the workload a budding orchardist will then have. Many orchardists let nurseries do all this work for them, and purchase the established tree with the specific desired varietal and roostock for roughly 10x the cost and are left to plant the trees and begin training them.
Happy grafting and do make a note below if you have any more suggestions based on your own experiences grafting!
References | Fruit & Nut Tree Propagation
Don’t listen to me, research from experts with far more experience out there! Below is a list of resources I have found invaluable in our propagation practices.
Plant Propagation – Principles and Practices by Hartmann, Kester, Davies and Geneve
This book is basically all you need to launch yourself on the way to becoming a propagation expert. It has every sort of propagation for every sort of plant you could dream of.
Also note that each image above has been linked to its source, and each of those sources are going to be great help to dig further into the topic for the reader.