Vegetative Propagation by Layering

Stems that are attached to their parent plant are capable of forming roots on coming in contact with a rooting medium. Layering exploits this property of stems. It involves development of roots on a stem while the stem is still attached to its parent plant. A layer is the rooted stem following detachment from the parent plant.

Many plants like Strawberry and Raspberry are propagated by natural layering method. The natural layering occurs because these plants form runner, which are soft horizontal stems running above the ground. Wherever the ends of such runners touch the ground, new plants are formed at those places. In this way, many more strawberry or raspberry plants are formed from the parent plant in a natural way.

Timing for Layering

The best time to perform layering is when the plant is in its dormant stage. For must shrubs, layering should be done in spring so that the adventitious roots are formed by fall, when the plant is in its active stage. Shrubs with flexible stems are best suited for layering.

Types of Layering

1. Simple Layering

Simple layering can be done on most plants with low-growing branches. To perform simple layering:

1. Make a Cut: Make a 1/2 to 3/4 inch cut through the stem 3 to 5 inches from the tip
2. Dig a Hole: Dig a shallow depression in the ground and bend the branch so that the cut portion is into the soil. Cover it with soil, leaving the remaining 6 to 12 inches above the soil
3. Bend: Bend the tip into a vertical position and pin it into the soil using a landscaping pin or a brick
4. Support: Insert a small pebble or toothpick into the cut to keep the cut open and if desired, apply a rooting hormone

The sharp bend will induce rooting. Wounding the lower side of the bent branch will also speed up the process. Be sure to keep the area moist. Once you can see well developed roots coming out from bent branch, simply cut the new branch away from the parent plant, dig it up and move it to the desired location.

2. Compound Layering

Compound Layering is similar to simple layering with little variation. It is suitable for plants with long, flexible stem. The stem is bent into the ground every few inches, giving an impression of a serpent. The advantage of this variation is that allows several plants to be produced from a single plant at a time.

3. Tip Layering

Tip layering involves inserting tip of the shoot into the soil. The tip will grow downward first and then it will bend sharply to grow upward. Roots are form at the bend. The re-curved tip forms a new plant which can be separated from the parent plant and planted elsewhere.

4. Air Layering

This method is used for thick-stemmed houseplants that have lost their lower leaves and have become leggy. Most of the Citrus trees can be propagated by air-layering.

You will need a knife, thick cotton thread, plastic sheet and a saw. To perform air layering:

1. Select Branch: The branch should be healthy and free from any pest attacks. The best time to do air-layering is when the plant starts growing new leaves
2. Choose a Spot: Leaf growth will occur above the point of layering, so choose a spot on the stem where you want the soil level to be
3. Make deep cuts: Make two clean cuts around the branch about one inch apart with a sharp knife
4. Peel off the Bark: Peel off the bark between those two cuts
5. Surround with Soil: Make a ball of soil mixed with tree moss or soil mixed with sand and wood ash around the area where the bark has been peeled off
6. Wrap: Wrap the soil with a plastic sheet of right choice.
   Tie the ends tightly with cotton thread, so that no water or air can enter

It may take up to eight to ten weeks for roots to appear. After that you can cut the stem just below the bottom of soil wrap and pot the layer. The new plant will require some pampering until the root system becomes more developed.

Advantages of Layering

1. Grow Multiple Plants: Many plants can be produced from a single plant at a time
2. No Special Equipments: Layering doesn’t require any special equipment or skill
3. Less Care: New plants do not require much care till they are connected with the parent plant.  The propagated portion continues to receive water and nutrients from the parent plant while it is forming roots.
4. Improve Roots: The technique can be used for both creating new roots and improving existing roots

The layering method is used for propagation of plants like: Jasmine, Strawberry, Raspberry, Lemon, Guava, Hibiscus (China Rose), Bougainvillea, Bonsai and many slender ornamental plants.

Reference Links:

1. http://www.ces.ncsu.edu/hil/hil-8701.html
2. http://www.urbanfarmonline.com/urban-gardening/backyard-gardening/4-ways-to-grow-your-garden-without-seeds.aspx
3. http://en.wikipedia.org/wiki/Layering
4. http://www.thriftyfun.com/Propagating-Plants-by-Layering-1.html