Propagation

Air Layering: Propagating Difficult-Rooting Plants


Air layering point wrapped with plastic

Perhaps one of the most important propagation methods to have in your gardening toolkit is air layering. You may already know you can divide plants, and propagate by seed, or by cuttings, but understanding the process of air layering plants is different and useful. 

Air layering is not just for houseplants. While your parent plant can be a houseplant, air layering propagation is effective on many woody plants, vines, ornamental plants, and even fruit trees and shrubs. All it takes is a little wound in the mother plant, some sphagnum moss, a good wrap, and you’re well on your way to a whole new plant. 

So let’s discuss air layering. We’ll talk about the scientific process behind propagating plants with air layering, and how to air layer, with indoor plants and outdoor plants too.

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What is Air Layering?

This technique dates back to ancient China and Japan, where air layering bonsai was popular. It’s not the most common propagation technique by any means, because it takes a while for a cutting to grow when it’s air layered.

So, why choose this method over another type of propagation? Clearly, growing from seed is easier, right? Well, yes and no. Seeds are simpler to start but take much longer to reach maturity and are not genetically identical to the parent plant.

If you want an exact copy of a particular plant you love, you have to propagate it directly to clone it. Air layering uses existing plant material to create new roots, so it produces genetically identical clones.

This process occurs in nature without human intervention. If a plant’s branches droop and touch the ground, sometimes they’ll produce roots. This new stem is identical to its parent and can be severed from the parent to form a new plant.

The Scientific Process Behind Air Layering

Layers of bark
The many layers of a plant stem. Source: Parton Barksiding

During the propagation process, you remove a 1” wide section of the outer layers of a plant stem (bark, cambium layer, and phloem) in a process known as girdling. Then, you apply a rooting hormone to the area to stimulate root growth from the cut area and wrap the area in sphagnum peat moss to retain moisture. Finally, you wrap the moss in a plastic wrap of some kind and secure it with rope or string.

By removing these sections of the plant, you prevent nutrients from moving below the cut area. However, water and nutrients can still move up to the area. This means that the leaves on the stem will remain healthy, and the buildup of nutrients at the cut site (along with rooting hormone) will activate what is known as adventitious buds, causing them to produce roots. Once these roots have developed enough, the stem can be cut off the parent plant and planted elsewhere.

Air Layering vs Taking Cuttings

The only difference between air layering and taking cuttings is the stem is completely removed when you take a cutting. Propagation by cuttings is a better technique for smaller, younger stems as they often survive via capillary action that delivers water and nutrients to the plant. Hardwood cuttings are easier to prop via air rooting.

Air layering allows you to propagate from a large stem or branch by forcing the stem to produce roots at the cut area.

How to Air Layer Plants

Now that we’ve discussed air layering in general terms, let’s cover the step-by-step instructions for carrying out this propagation method. You’ll find there are several different ways to accomplish the goal of creating a plant from a stem or branch that takes root and becomes an identical copy of its parent. 

On Timing

One very important thing to remember when you’re practicing air layering propagation is to do it at the right time. Especially if you’re working outdoors or with fruit trees, you don’t want to select a branch during dormancy – in cold winter, or hot summers. Instead, work with propagation in early fall and mid-spring, when active growth cycles aren’t slowed by weather extremes. While you may still succeed in mid-summer and winter, you’ll have the most success in a temperate season. 

Gather and Prepare Materials

Most of the materials you need to air layer are already around your home, except for the rooting hormone. While rooting hormone can speed up propagation time, it’s not mandatory, and plants will propagate without it.

  • Sharp, sterilized cutting instrument: any sharp knife, budding knife, Felco 2 pruners, etc.
  • A moistened growing medium: sphagnum peat moss, or coco coir
  • Rooting hormone (optional)
  • A covering: plastic bag, plastic wrap, polyethylene film, or aluminum foil
  • Small piece of thin hard plastic: a piece of a plastic bottle or something similar works
  • Something to affix your covering: string, garden twine, floral ties, twist ties, 
  • Scissors
  • Water
  • Bowl

After you successfully propagate your plant, you’ll need:

  • Pot/garden plot
  • High-quality potting mix or garden soil
  • Stake and/or string

Once you have all your materials gathered, soak your sphagnum moss and squeeze out until moist, but not soaking. You should have a damp moss ball about the size of a tennis ball. If you have rooting hormone handy, add it to the water you soak your moss in to spur root growth.

Cut a sheet of plastic or aluminum foil to about one square foot and put it aside. Cut two pieces of string long enough to wrap around the stem on both sites. Choose the stem on your plant that you want to propagate and the section you will cut. A good rule of thumb is to cut 4 to 6 inches below a node.

Make Your Cut

Layering point stripped and coated with hormone
Air layering point stripped and coated with a rooting hormone. Source: velacreations

Now it’s time to air layer! With a sterilized knife, make a 45-degree cut through at least half of the branch, but no more than two-thirds. Support the other side of the branch as you cut, but keep your thumb in a position where it won’t be sliced if you accidentally cut through the branch!

When you’re air layering in plants with woody stems, or if you’re air layering trees, make two parallel cuts with your sharp knife, and then scrape away the top portion of the ring of bark. Penetrate through the top ring of bark with your knife, making contact and exposing the green layer underneath. This process is called air grafting. 

Insert the Plastic

Take your small piece of cut plastic and slide it into the cut. This prevents the plant wound from healing itself and sealing the cut over the next few weeks.

Wrap With Moss or Planting Media

Grab your moist sphagnum moss or coco coir and firmly press it around the stem. It should surround the stem and be firm, but not extremely compressed. Over the next few weeks, the cut area will send new roots into the moss, giving you a nice little root ball to pot up or plant directly in the garden soil.

Wrap With Plastic

Hold the moss in place around the stem, and cover the moss with plastic wrap, foil, or polyethylene film. Take your pieces of string, floral ties, twist ties, or even gardener’s tape, and wrap them around the top and bottom a few times, then tie them tightly. You may want to stake or tie up the top side of the branch, as the severity of the cut might weaken its ability to stand on its own. Make sure the ties are tight enough to keep the moss in place, but not so tight they restrict the growth of new roots around the stems.  

Sever the Branch

Wait at least a few weeks. Air layer roots develop in most plants within a few weeks. In some cases, new roots form in months. Monitor your progress by looking through the plastic wrap to see if there are roots forming. If you’re working with foil, peel back the wrap gently to see how your air layers are developing. When you see a critical mass of air-layered roots that are at least two inches long, sever the branch from the plant completely by cutting about 1inch below the site.

Plant It!

Once you sever the stem, remove the wrap. Do not remove the moistened sphagnum moss ball — remember, this is where all the roots are! Pot up your plant in a small pot with high-quality soil. Keep the pot small so the soil doesn’t have excess moisture for too long. The last thing you want is to rot the roots of your newly air-layered plant, especially after all the time you put into getting it to this point! This is especially true for indoor plants. 

For hardier plants that aren’t as susceptible to rots and root more easily, you can plant a rooted stem or rooted branch of one of them directly in your garden plot. This method is a quick and easy way to clone salvias, and lantanas, for instance. But many plants benefit from their new roots being potted for a short time after the air layering is complete. 

Plants That Can Be Propagated via the Air Layering Technique

Now that we’ve discussed air layering plants and how to air layer, let’s cover the plants you can propagate via this method. If you’re interested to know how to go about air layering, try one of these, and follow our steps above. You may notice many tropical plants on this list.

It’s also a popular method for fruit and nut trees like:

Tip Layering

Another layering method that is not air layering, is tip layering. Here, instead of coir or moss, you’ll wound the stem of the plant, removing the top layer of bark in basically the same way. Then you pin it in the garden next to where it is growing and cover it with growing medium, or compost.

When tip layered, or ground layered plants grow roots that are at least two inches long, you can detach the wounded stem from the plant, and move it elsewhere. If the plant is sensitive to excess moisture, pot it up separately and keep it out of direct sunlight in a good quality growing medium until it is well established. 

This and other methods are preferred above air layering in a perennial garden where woody plants reign. Several outdoor plants can easily be propagated this way. I have a cat mint plant that can attest to this very fact! After several of the neighborhood cats sat on the plant, it spread in the process. This also suggests that ground layering could simply be a form of helping your plants spread, rather than propagating them. 

This is also the prop method most commonly used for the rubber plant, strawberry plants, boysenberries, and dewberry. The key here is the plants should be quick to root, and many of the plants listed here can be propped in this way as well. 

Frequently Asked Questions

Air layering point wrapped with plastic
Air layering point wrapped in moist peat and plastic. Source: velacreations

Q: What is air layering method?

A: Air layering plants is a way to produce aerial roots on a wounded branch, which when detached and planted form a clone of the parent plant.

Q: How long does it take for air layering to root?

A: It can take anywhere from a few weeks to a few months, depending on the plant. 

Q: What are the steps of air layering?

A: Cut the plant, cover the wound, wrap it with damp sphagnum moss, wrap the moss, affix, and wait! Then detach and plant. More explanation of this concise how-to is in the How To Air Layer section of this piece. 

Q: What time of year is best for air layering?

A: It’s best to carry out air layering in temperate seasons. 

Q: What plants can be air layered?

A: There are so many. We have a list of specific plants in this piece. But many woody plants, fruit trees, tropical plants, and herbaceous plants can be air layered. 

Q: What soil is best for air layering?

A: The best media for wrapping your wounded stems are sphagnum mosses. 

Q: What are the disadvantages of air layering?

A: It does take some time. So bring your patience with you when you try it out. 

Q: Can you air layer any tree?

A: Not necessarily. But you can air layer many trees. 

Q: What is better: grafting or air layering?

A: It depends on the tree and which prop method it is most suited to.

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