"Cliff's Notes" for Propagation Clinic
I am posting here an essay I wrote for those of you who might have liked to attend my free clinic tomorrow, but already have other plans on your calendar. Feel free to reach out with any questions.
Free Plant Propagation Clinic Grumpy’s Garden Club
May 21st, 2022 written & hosted by Steve Hill
It his book titled, Secrets of Plant Propagation, Lewis Hill wrote, “By planting a seed, rooting a cutting, attaching a graft, and the other myriad of activities of plant propagation...you are involved in the process of creating new life - that awesome natural force that is far beyond man’s understanding.”
Plant propagation is a fascinating sub-category of gardening - like gardening distilled. These advanced gardening practices give us the ability to cultivate the specific plants we love the most and in quantities that are truly exponential if desired.
I will begin this essay with defining my terms and explaining how “propagation” is distinct from both cultivation or germination of plants.
Propagation is simply defined here as the “intentional and controlled reproduction of desirable plants”. If you have divided strawberry root-crowns, dug up “volunteers” in a blackberry patch, or separated crowded aloe vera plants into new pots then you have already engaged in some plant propagation on a small scale. Propagation can be starting plants from seed, or it can be cutting parts off of a plant and suspending them in a humid environment until they produce roots. The idea behind propagation is that we are in charge of the reproduction process. Cultivation is care that promotes the growth of plants & germination is sprouting seeds.
6th grade science may have taught us that plants can reproduce using two different biological processes: Sexual & Asexual reproduction. However, the plants that result from each of these two methods are very different.
With sexual reproduction the genetic material from two different individuals comes together to create a completely new individual. In plants, this happens during pollination of the flower and results in fertile seeds. However, not all plants reproduce best by seed, and the germinated seeds will not result in plants bearing the exact traits of their parents. Occasionally, the offspring possess more desirable traits like the Fuji Apple, or the Hass Avocado. But far more often that is not the case and the offspring will be less desirable than the parent.
Heirloom seeds are types that have been “stabilized” by open-pollination for generations. Each seed is still a unique individual, but the common traits are so homogenized that the variation from one individual to another is very minimal. Heirloom seeds are similar to carefully curated dog breeds with a proven pedigree.
Hybrid seeds are more recently developed varieties that have been carefully cross-bred between two parents having desirable characteristics. The seeds are most often first-generation offspring expected to possess the targeted combination of desirable traits from each parent. Due to genetic drift, the hybrid seeds are only “good” for one generation. If you save the seeds from hybrid fruit - they will not produce that same fruit the next season. If you plant hybrid seeds and really like the characteristics of the plant that grows from them you will need a different method in order to keep those genetics going for future crops. You will need to clone.
Asexual propogation involves isolating a part of the parent plant and using that tissue to generate a copy of the parent. This potentially allows the genetics of the parent to carry on indefinitely in the life of all future clones.
Asexual propagation is accomplished many different ways and each method has it’s strengths and weaknesses. Today, I will explain three different asexual propagation techniques that I use to clone plants.
In this clinic we are only interested in asexual propagation because it is assumed we have “mother” plants with desirable characteristics that we wish to duplicate. In future clinics we hope to discuss the fascinating art of selective breeding whereby new varieties of plants can be developed with unique characteristics all their own.
There are several different methods of Asexual propagation, but today we are going to focus on two of the simplest and most practised methodologies: Layering and Rooted Cuttings. Both of these types can be accomplished using several different techniques. I have experienced good success with what I will share.
Layering is a propagation method that takes advantage of a natural feature of many plant species where the tissues will begin to form root cells at the point where they make contact with damp soil. Layering in its most basic form happens all the time unaided by humans where a low hanging branch touches the ground and becomes rooted to that spot. This is one way in which groves of trees or masses of shrubs form in the wild.
This is the simplest way of generating a clone, but it requires having branches long enough to reach the ground and that is often not possible when plants typically grow toward the sun.
Air layering is a variation of common layering in that this technique brings the soil up to the branch. Typically, the technique involves creating a watertight chamber containing moist, soilless media wrapped around a wounded branch. This technique “tricks” the plant into thinking it is touching the ground. The plant responds by generating roots inside the chamber during the growing season. Prior to entering dormancy in the winter, the chamber and a part of the branch are removed from the main plant and potted up - resulting in a new self-supporting plant and a genetic clone. The biggest advantage to this technique is that the rooting takes place while the branch is still attached to the mother plant supported by its existing roots and leaves. There is virtually no stress to the mother plant, nor are the baby roots taxed with supporting leaves. It’s kinda foolproof.
I researched what other gardeners have done and combined several air-layering ideas to create a simple, inexpensive, and highly effective technique for myself. I have experienced success rates of well over 80% every season I have used it - even with plants that are notoriously difficult to clone, like Muscadine vines.
The materials needed for our Air-Layering packets include the following:
Food-grade plastic bags: We buy model “S-5390” from Uline: 6” x 10” - 1,000 bags for $19
Perlite - This volcanic mineral can be purchased from any garden center in various quantities.
Peat Moss or Coconut Coir - it does not matter which material you use.
A Clean, Sharp Knife or pruning shears
String or Bailing Wire about 18” long
The Air Layering Process:
It is most effective to begin air Layering in the Spring so the branches have maximal time to produce new roots before the winter sets in. Some plants like evergreens cannot be successfully air layered at any other time.
Prepare your soil-less medium by mixing 50% dry perlite with 50% dry peat moss (or coconut coir) into a container until thoroughly mixed and there are no lumps or chunks.
Add water to the mixture to dampen it and let it rest for several minutes so that the water can soak into the material. Mix the material as you add water so that all parts receive moisture.
This may take several attempts to get the right level of moisture.
You do not want the material to be soggy and heavy. You want the material to be thoroughly damp or moist, but not so wet that you can easily wring out water by squeezing it in your hand.
There is no substitute for patience in this process. Peat moss or coconut coir can absorb a great deal of water, but it happens so very s-l-o-w-l-y. Rushing the absorption will result in dry spots or a medium that is too wet and leads to problems with rot or root failure.
While the soilless media is resting, prepare your plastic bags by inserting a knife or scissors into the bag along the seams about halfway down the length of the bag and cutting the seam open from the midpoint to the top. When you have slit the plastic halfway down both seams you should end up with a bag that can now only be half-filled and has two long flaps at the opening.
Place about 1.5 - 2 cups of moistened, soilless mixture in each prepared bag and fill it gently so that it is not too dense.
Choose a 1 or 2 year old stem that is straight, healthy, and vigorous. Trim off the leaves and side shoots from a section of the stem that is between 8” and 12” long.
At the middle of this trimmed section use the edge of a sharp, clean knife or shears and scrape away just the outer layer of bark until you can see the lighter wood of the cambium layer. Do not scrape the bark off of the full circumference. Just a small section of damage will be enough to expose the cambium to produce a callus where roots will form.
While it is not necessary, some gardeners will dip or coat the damaged tissue in Rooting hormone. We have had much success without that extra step and expense. However, you may wish to do it if it will help ensure that your efforts are successful.
Tear off a piece of duct tape about 10” long and have it ready in a handy spot. You will need to have it close so that you can reach it and apply it with only one hand free.
Bend the stem enough that it can be inserted into the bag and the damaged bark can make good contact with the media. I push the branch into the mix so that it ends up at the middle of the mixture.
Wrap the loose plastic flaps tightly around the stem and pull them over the bag - wrapping them around the media package. Place the duct tape around the wrapped bags tightly so that air and water can not easily get into the moist media. This takes practice, but once you understand the concept you will be able to adapt it to any plant and find your own way to succeed. Plan on making more than you need.
Finally, tie the string or bailing wire around the middle bulk of the bag and the stem in such a way to support the weight of the package without straining the point where the branch is still attached to the mother plant. This is done to keep the weight from breaking the branch off in high winds. That kind of damage has caused failures for me in the past.
Check on the air-layering package at least every few weeks to make sure it is not taking on too much rain water, or drying out too quickly. Otherwise, you can leave these packets alone until late Fall.
Prior to the first expected hard freeze of the winter season you need to cut the branch free from the mother plant and trim the leafy branch tip coming out of the bag so that only three or four total leaves remain. This helps to balance the quantity of new roots to the leaves they must support.
Pot up your new plant in an appropriately-sized pot using high-quality potting soil & protect from freezing that first winter. I keep my clones outside and on the ground against the South side of a building where they can receive rainwater. I do not supplement their water at all until Spring.
Do not fertilize the new clones until April 1st and do not let them produce fruit the first season for best vigor.
I have found that the best time to establish air layers in North East Texas (Zone 8a) is between June 1st and August 1st. It is difficult to find stems vigorous enough to support the media packages prior to June 1 and air layers started after August 1st do not typically have enough time to form strong enough roots before the first frost. So, we typically mark the calendar so that we always know the period from June 1 to August 1 is when we will be setting up air layers in the vineyard or nursery.
This becomes part of an annual garden rhythm.
Some other helpful tips concerning air layering include:
Be mindful of sun exposure on the surface of the bags. Plastic does not stand up well to UV light and solar heat gain can be a root killer. Try to place your air layers where they will be protected from direct afternoon sun if possible. If that is not possible, consider painting the bag with white latex paint.
If you notice that the media has dried out in one of your bags, there is nothing wrong with adding water to it using a turkey baster. Try to find out why the moisture is escaping and correct that with duct tape.
Each air layer package will have two points where the stem penetrates the bag as it passes through. Make sure when you remove the package from the mother plant that you cut the stem at the right place. You want to disconnect it from the mother. Don’t accidentally decapitate your new plant.
Failing to trim the tip of the new stem is not the end of the world, but it will stress the new roots next spring when the plant comes out of dormancy. You only need to keep two or three nodes, I promise.
It is crucial that you understand the balance between the visible portions of a plant and the invisible roots that support it. You gain nothing by trying to keep a lot of leafy top growth if there is not enough root structure to supply those leaves with water and minerals. This is a common mistake!
Water the plant as soon as it is potted up to make sure there are no air gaps in the soil, however, watering throughout the winter months is usually not necessary. Inspect new plants often to be sure.
Do not fertilize until the Spring. You want the plant to remain dormant so that it can build core roots.
If you have a permanent location in mind for the new clones there is no need to pot them up first.
Pros & Cons of Air Layering for Plant Propagation:
The process does virtually no harm to the mother plant.
The mother plant provides all the support the baby plant needs as roots develop.
Watering the media is usually not required. This is typically a very trouble free system.
Very high success rate (>80%) with low cost in materials and work.
The process requires at least 8 weeks for viability of the clone, sometimes longer.
The work must happen out in the field at the location of the Mother plant.
Difficult to produce large quantities of clones without access to many identical mother plants.
Clones must be protected from extreme temperatures because they are not connected to earth.
Pros & Cons of Common Layering for Plant Propagation:
Usually no cost involved at all.
Does not require protection from extreme temperatures because the earth is a heat sink.
This is very easy to do.
Requires a branch long enough to reach the ground - not every plant is a suitable candidate.