What Is Air Layer?
Air layer refers to a type of plant which grows underground and absorbs water from the soil. The plant then releases it through its leaves or flowers when they are touched by raindrops falling on them. This method of survival is called evapotranspiration.
The term “air” in this case means the atmosphere and not oxygen, which is only present at high altitudes where there is little sunlight. Evaporation of water vapor from the soil occurs because the temperature difference between the ground and air is greater than what would occur at lower elevations. Soil moisture content decreases with increasing altitude due to less solar radiation reaching the surface. At higher elevations, the amount of available energy (heat) is greater than at lower elevations.
Therefore, evaporation takes place. Water vapor molecules are able to move faster than water molecules without oxygen. Thus, the rate of evaporation increases with height above sea level.
Evaporative cooling is one way in which plants cool themselves during hot summer days and cold winter nights. It allows them to carry on with life activities, photosynthesis, growth and development.
Air layering is a procedure in which a plant is grown without making any roots from the stem section. The process involves removing a portion of stem, rooting it and taking care of it as a separate individual. Though the name suggests that the process involves air in some way, this is not exactly true. In reality, it simply involves allowing the stem to dry out.
It can be a tricky process for the uninitiated, but with some patience and care it can be mastered by anyone.
The plant is made to form roots on its stem. This is done by removing an internodal section of the stem (the portion which connects two nodes) and keeping it in a wet medium (soil, sand, sawdust mixture, etc.) With the help of small incisions at each end of the stem, root formation can be stimulated. After some time, roots will start to develop and the plant can be potted up individually.
The portion of the stem from which roots developed is severed from the parent plant and can be planted in the ground.
How To Air Layer?
These are the steps involved in air layering:
Choose a stem that is from the previous year’s growth and is well-fleshed. The fleshing of the stem means that it has enough space for roots to form along with woody portions.
Cut off the stem that is going to be layered so that only 4 to 5 leaves are remaining above the cut.
Remove the uppermost leaves and make an incision in the stem so that it is oozing out some sap. It is important to keep the upper portion of the stem moist since it is the point of origin of roots which are going to develop.
Create a bed for the layered stem by placing some slightly moistened sphagnum moss or perlite in a small pot.
Put the stem in the pot so that the incision is just below the surface of the moss or perlite. If there are two nodes (leaf scars) below the incision then place the stem so that the second one from the bottom is at the surface level. This will ensure better formation of roots.
Cover the stem with more moistened moss or perlite and place a plastic bag over it to hold in the moisture.
The stem should be checked every few days to see if rooting has occurred. When this happens, the plastic bag can be removed and the stem can be potted up into a bigger container after the roots have developed more.
Advantages Of Air Layering:
Though there are quite a few techniques for increasing the size of plants, air layering is easily the most effective one. Since there is no damage done to the original plant, it can be used over and over again on the same plant.
It is also helpful in controlling the size of the plant since only a portion can be layered to make clones. The new plant starts growing very quickly and can easily be propagated.
Air layering is a great way of propagating plants that are difficult to clone or root from cuttings such as some bamboos, begonias,and ixoras.
The layered stem can be used immediately or stored in damp sand for later use.
Disadvantages Of Air Layering:
The only real disadvantage of air layering is that it can be a bit tricky to get right at times. It is essential to choose stems that have multiple nodes where leaves emerge such as peach and nectarine trees.
Also the upper portion of the stem should be between one-quarter and one-third inches in diameter. If the stem is too thin, it may not have enough tissue for roots to form. If it is too thick, the inner tissues may not get enough oxygen and the rooting will be uneven.
Large trees should only be layered in late winter or early spring and in areas with warmer weather where the season is long enough for them to root.
Air layering is not appropriate for all plants but for those that it does work on, it can double or even triple the size of a plant in one growing season.
The most important thing to remember when air layering is to keep it simple. It is better to make a few cuts rather than going overboard and complicating matters.
Air layering is an easy, effective way of multiplying plants. It can be used by anyone with a bit of patience and luck.
Sources & references used in this article:
Effect of plant growth regulators on rooting survival of air layering in litchi. by AK Das, P Birendra – Advance Research Journal of Crop …, 2014 – cabdirect.org
Success of air-layering in custard apple (Annona squamosa L.) as influenced by ringing of shoots and growth regulators. by RS Chovatia, SP Singh – Orissa Journal of Horticulture, 2000 – cabdirect.org
Air layering in Prosopis cineraria (L.) MacBride. by KR Solanki, NL Kackar, SK Jindal – Indian Forester, 1986 – cabdirect.org
Air layering in forestry practice. by K Kadambi, SN Dabral – Indian Forester, 1954 – cabdirect.org
Evaluation of different organic media and water holding materials with IBA on rooting and survival of air layering in guava (Psidium guajava L.) cv. Allahabad Safeda. by RK Maurya, NR Ray, JC Chavda… – Asian Journal of …, 2012 – cabdirect.org
Vegetative propagation of dhakijam and garjan by air-layering. by MH Rashid, M Serajuddoula – Bano Biggyan Patrika, 1984 – cabdirect.org
Air-layering studies in some forest trees. by PK Khosla, PS Chauhan, R Sood – Indian Journal of Forestry, 1979 – cabdirect.org