On April 23 2018 East Van Bonsai hosted an air-layer demo lead by Peter B. Here are some photos and words regarding the layer done on a big larch. Assuming all goes to plan, Peter will revisit the larch in August. Hopefully enough roots will have formed by then to remove the layer in the same year.
Tools and supplies used; Sharp knife (box cutter). Aluminum wire. Clear plastic. Sphagnum moss. Rooting hormone. A brush to paint on the hormone.
Step 1. Begin by soaking the moss in water for at least ten minutes.
2. Decide on the location to make the cut for the layer. Marking the bark with chalk can be helpful in marking your line.
3. Using a clean sharp knife(box cutter or grafting knife) cut around the circumference of the branch. Many people suggest making the size of the cut twice the diameter of the branch. The top cut is where new roots will emerge. Cut deep enough past the green cambium layer. Be sure to scrape away all white, pithy wood. Leaving too much behind can easily cause the tree to bridge the gap.
4. Fasten the clear plastic to make a bag around the branch. Put the bag around the branch leaving the top open to add the moss.
5. Apply rooting hormone around the cut, along the top where the roots are desired.
6. Remove handfuls of wet moss from the water. Squeeze out excess water from the moss. The moss should lose most of the moisture before placing it in the bag. If water drips from the moss, it’s too wet. Continue filling up the bag with moss.
7. Once the bag is full, seal it up by overlapping the plastic or securing it with tape. It’s helpful to tie and secure wire around the top and bottom of the air-layer bag. Tighten the wire firmly to hold the bag, but not so tight to bite the bark.
8. Wrap the bag with cling wrap. Go around the entire air-layer a few times, putting pressure to tighten everything. The pressure on the moss against the cut helps roots to form.
9. Poke a few holes around the lower area of the bag. This allows any water to drain in case the air-layer bag gets flooded.
10. Protect the bag from direct sun. If the tree being layered is in a bright location, cover the clear plastic with aluminum foil.
If an air-layer is done correctly, one can achieve success on many different tree species, provided that the tree produces back budding and is in good health. East Van Bonsai will post a follow up article when the larch is removed.