Saturday, July 25, 2009

Double Wall Potting Technique - A Tutorial

This tutorial shares a technique that I used with good success to propagate bay laurel trees. The example here is an attempt to use the process to multiply lavender. You will need to stay tuned for future updates to see how well it worked.

The process requires two clay pots that differ slightly in size. In this instance I used a 4-inch and a 6-inch pot. It is the size combination that I use most often, but other sizes work well too.

Pots do not need to be new, but they must be clay for this process to work well.

As you can see, a cork has been placed in the pot hole. Sometimes I do this with both the small and the large pot, or sometimes only in the smaller pot. It is crucial that the smaller pot is plugged with a cork.

There are several places to find corks. They can be purchased in the section of home improvement stores that have packaged nuts, bolts, cotter pins and the like. You may need to ask for help to locate them. In a pinch (you know, a plant propagation emergency), I have used a pocket knife to shape a used wine cork to the appropriate size and shape.

A little dirt goes into the larger pot, enough so that when you place the smaller pot inside the larger one, the upper lips of both pots will be about level.

Next, the space between the two pots gets filled with a light potting mix or seed starting mix.

When I do this, some soil invariably ends up inside the smaller pot as well. This will hurt nothing, but if you have tidiness issues, there is a simple solution.

The soil mixture between the pots should be well tamped down. Lift the smaller put out. Dump it and replace that smaller pot.


Here I am using the pruned portions of an old, established lavender to start new plants. This process works to propagate both soft wood and and hard wood cuttings. Those are simply done at different times. Soft wood cuttings are taken during a period of active growth and hard wood cuttings during the period of dormancy, so late fall or early winter.

The lavender is cut into more manageable sections.

These are the final bits of the plant that will be put into the pots to propagate. As this is my first time trying this with lavender, I experiment a bit, using different lengths and trying both tip cuttings and heel cuttings.

Cuttings must contain a leaf node on the remaining stem. This is where new roots will grow.

Cuttings can be dabbed with rooting hormone prior to placement in pots, but I have also had success without it. Here I am using a wooden skewer to make a hole to insert my cuttings.

In the last step, the small inner pot is filled with water. The small pot is kept full of water. In several weeks, when the shoots show new growth they are potted into individual containers.

Almost one month later

This process started at the end of June, after visiting Beagle Ridge for the Lavender Festival. It is the pruned portion of their plant that was propagated here. It was gathered with permission to propagate.

As you can see in this last photograph, only a few of the shoots started. I have had better luck propagating bay laurel and other things. That leads to a discussion of things that can go wrong. On hot summer days, the outdoor cats quickly find this handy source of drinking water and can be seen lapping from the inside pot.

In this instance, my spousal unit plunked some of those dunks that prevent the maturation of mosquito larvae into the pots. The dunks are supposed to be environmentally safe and friendly, but I have to wonder if that did not interfere with the development of roots. One answer to both concerns would bet to put mosquito netting over the top of the smaller pot.

As a result of my efforts, I have gained a few very inexpensive lavender plants and obtained enough photographs to instruct others in this technique. If I try to propagate lavender again next year, I will probably employ rooting hormone which may increase my success.

This process does work well to propagate a variety of plants, so give it a go if you are so inclined.



  1. That is a great tutorial! I am going to have to try it because I love lavender and would like nothing more than to have a whole farm of it! I wonder if this technique would work with rosemary too? Very cool and thanks for all the tips.

  2. The biggest thing I learned about laveder is that it needs really great drainage and very low soil fertility. Ellen at Beagle Ridge literally plants it in "dirty crusher run limestone." It's a type of gravel!
    It's worth a try with rosemary. Let me know how it goes.