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Horticulture 1000
HT1093 - Plant propagation 3 - Layering
Division Conditions required for successful asexual plant propagation
2

Layering

Layering is a form of asexual (vegetative)  propagation. It involves encouraging root development on a stem  while the stem is still attached to the parent plant.

Reasons for layering plants:

  • you can layer plants that don't grow easily from cuttings
  • the layered stem still gets water and nutrition from the parent plant until it has roots and can support itself
  • layering is used to propagate plants that can't be propagated easily by other methods, for example some large rhododendrons.

Ground layering

Rosemary Rosemary.

Plants with low growing trailing stems can be ground layered. This type of plant naturally layers so a plant propagator can take advantage of this growing habit. You can ground layer blackberry, ground cover rosemary, azaleas, rhododendrons and carnations.

Here are the steps used in ground layering.

Choose a healthy, young stem growing close to the ground Choose a healthy, young stem growing close to the ground.
  • Choose a healthy, young stem growing close to the ground. It must be flexible so it can be bent down to lie along the soil surface.
  • Remove the leaves from the area to be layered.
Slip a matchstick into the cut to keep it open and expose the cambium tissue to the soil Expose the cambium tissue to the soil.
  • On the underside of the stem, make a small cut one third of the way through the stem. This exposes the cambium tissue where the roots will form.
  • Dust the cut with rooting hormone powder.
  • Slip a matchstick into the cut to keep it open and expose the cambium tissue to the soil.
Peg the stem to the ground Peg the stem to the ground, cover the cut in soil and keep it damp. This allows roots to form from the cambium tissue.
  • Peg the stem to the ground, cover the cut in soil and keep it damp. This allows roots to form from the cambium tissue.
  • Some leaves may need to be removed from the end of the wounded stem to prevent wilting.
  • Attach the upright stem of the layered stem to a stake. This will help it grow upright.
Cut the new plant from its parent when a root system has grown Cut the new plant from its parent when a root system has grown.
  • Cut the new plant from its parent when a root system has grown.
  • Plant the new plant in fertile soil and keep it moist.

Air layering

Air layering involves a stem being layered above ground.

The plant produces roots on the layered stem while it is still attached to the parent plant.

A rubber plant A rubber plant.

This method is useful on plants without flexible stems that are difficult to bend down to the ground.

It is rarely used commercially in New Zealand because it is slow and only a few plants can be produced from one parent plant.

Tropical or sub-tropical plants may be propagated by air layering.

Suitable plants include the rubber plant, weeping fig, and New Zealand puka.

Here are the steps used in air layering.

Remove the leaves from a healthy stem 30 mm from the growing tip Remove the leaves from a healthy stem 30 mm from the growing tip.
  • Remove the leaves from a healthy stem 30 mm from the growing tip. The new roots will form here.
Make a diagonal cut in the stem that will ringbark it Make a diagonal cut in the stem that will ringbark it.
  • Make a diagonal cut in the stem that will ringbark it.
  • Dust the wound with root hormone and slip in a matchstick.
Cover with a plastic bag and tie firmly Cover with a plastic bag and tie firmly.
  • Cover the wound with damp sphagnum moss. Sphagnum moss holds water and is sterile.
  • Cover with a plastic bag or black polythene. Tie firmly. The black polythene excludes light and stops algae and fungi growing in the moss.
Pot up the new plant Pot up the new plant.
  • When a strong root system has formed, cut off the stem below the roots. This can take six to eight weeks.
  • Pot up the new plant.

Complete Activity 2A in your workbook

Key points   Key points

  • Layering is a method of asexual propagation in which a stem is made to produce roots while still attached to the parent plant.
  • The parent plant provides the new plant with water and nutrients while the roots are forming.
  • Layering can be used for plants that are difficult to propagate using other methods.
  • Air layering is used for plants with inflexible stems that may be difficult to propagate using other methods.

What's next?

Go to: 3 Conditions required for successful asexual plant propagation.

 
Division Conditions required for successful asexual plant propagation