We make a thousand or so air-layers or marcots every year and I am often asked how to make them. This site is in answer to that question.
To start with you will need: quart ziploc bag (1 for each layer)
some fine peat moss or sphagnum moss
some rubber bands cut once so that it is a strip(2 for each layer)
some rooting hormone, the brand and strength aren’t important for most plants. I use Dip N’ Grow full strength for most of my work: 2-Ounce Dip ‘N Grow Rooting Hormonesome regular size aluminum foil
some Parafilm M 2 x 250 feet to use as a sealant
a pair of pliers
a small paint brush
I choose a branch that is 1/2 to 3/4 inch in diameter and that is sloping upwards toward the tip. Smaller branches run the risk of breaking off before they are rooted and even if they survive they are less hardy than bigger branches. Larger diameters are fine but much of the foliage will have to be cut off when it is removed from the tree and potted.
Next I cut the bottom out of the ziploc bag so that it forms a plastic tube. Remove the leaves and any side branches from the branch you have chosen. Then I place the ziploc tube on my arm and use my hand to grasp and gently collapse the leaves on the branch so that I can slide the the ziploc tube off of my arm and onto the branch and down to the place where there is sufficient branch diameter.
Now I use my garden shears to cut bark down to the wood twice about 1 inch apart. Once the two cuts are made I use my pliers to remove that bark and rough the wood a little underneath. A little is enough. If you rough it too much you weaken the branch.