Learn Marcotting, It's Quite Easy
The asexual method of propagating crop plants by marcotting (or air layering) can be easily performed with less skill. Air layering is just slightly different from other methods of layering such as tip layering, simple layering, compound or serpentine layering, etc. In all these methods, the induction of root development is done by wounding the part of the plant to be rooted.
The following practical methods are common in propagating plants by marcotting:
1. Plant and Shoot Selection
A shoot with plenty of leaves is chosen from a healthy plant. The size of the stem at the part to be rooted is generally about that of an ordinary pencil, but this is not essential. Both the thickness and length of the stem vary depending on the plant part to be layered (trunk, branch or twig), the intended size of the air layer or marcot to be produced, and the plant species.
In roses, air layers are normally thinner. In herbaceous plants like aglaonema and dieffenbachia, the stem used in marcotting is always thicker.
2. Girdling and ScrapingThis procedure is skipped in bamboo and herbaceous plants. For trees, shrubs and semi-woody plants, a strip of bark is first removed from around the portion of the stem to be rooted. This involves pressing of a sharp knife against the bark preferably as close as possible below a node, moving the knife in circular motion around the stem. A similar cut is made generally about 2 cm to 5 cm below the first cut, but it can be wider with larger stems. The two cuts are then connected by a straight cut and the bark is pried loose and removed.
3. Slitting and Wedging
In herbaceous plants, a slanting upward cut is made up to the middle of the stem at the portion where the node is located. To prevent healing, a sphagnum moss, coir dust or a piece of wood is inserted into the wound to serve as wedge.
A slightly moistened sphagnum moss or coconut coir dust is placed around the debarked stem and wrapped with a piece of plastic sheet. A transparent plastic sheet is preferred to be able to see later if roots have developed. In many plant species, however, the stems can be marcotted even with pure soil.
The rooting medium may be as thick as 1 inch (2.5 cm) from side to side or bigger depending on the earliness to develop roots and size of the stem. The longer is the time required to induce rooting and the bigger is the stem, the thicker should be the rooting medium.
Both ends of the plastic sheet are gathered and tied securely against the stem, with one end just under the bottom part of the debarked stem (lower cut) and the other a short distance above the upper part (upper cut). It is important that the upper cut should be covered with the rooting medium because it is from this cut that roots develop
As an alternative, the plastic sheet may be placed first on the stem with one end tied just below the lower cut. The rooting medium is then inserted gradually and the upper end of the plastic wrapping is tied securely to the stem. This technique is more convenient and applies with any rooting medium which crumbles if not held by the hand.
To prevent breaking of the stem with big and heavy rooting medium, it is tied to another branch or to a stick attached to the parent plant.
A container can be made also with a relatively thick plastic sheet with the bottom gathered and tied just below the lower cut and the top is expanded to form a shape like that of a funnel. The sides are overlapped and stapled.
In plants which easily root like Ficus and croton or san francisco (Codiaeum variegatum), this funnel-shaped container can be made out of some thick leaves. The sides are secured in place by piercing with a stick. The container is then filled with rooting medium which is kept moist by regular watering.
5. Separation of the Air Layer or Marcot From the Parent Plant
The rooted shoots are severed from the parent plant when plenty of roots have developed. At this time the rooting medium becomes hard and rough when touched. New shoots will also have sprouted from the portion of the stem immediately below the rooting medium. In many plant species this occurs at least 15 days from marcotting.
The marcotted shoot is immediately potted into suitable container. The intensity of care that will ensure the successful establishment of the layers will depend on various factors such as size of the shoot, size of the rooting medium, and profuseness of roots. For maximum survival, the newly potted layers are kept under partial shade and high humidity.
By actually doing it, you will realize very shortly that marcotting is easy.