Simple layering is one of the easiest methods of propagating new plants. Unlike cuttings, which have to survive on their own, layered shoots are encouraged to form roots while still attached to the parent plant.
Some plants naturally self-layer, with shoots touching the ground rooting and forming new plants. Examples of plants with this ability include Campsis, ivy, Symphoricarpos and Hydrangea anomala subsp. petiolaris. The layering propagation technique takes advantage of this natural tendency.
Layering is an effective propagation method for plants that do not root readily from cuttings, such as Magnolia, hazel, Cotinus and flowering Cornus species. Other plants that respond well to layering include: Acer, Camellia, Chaenomeles, Daphne, Forsythia, Hamamelis, Jasminum, Rhododendron and azalea, Syringa and Viburnum.
Layering is best suited to plants that have stems that can be bent down to ground level. If this doesn't happen, try air-layering, a technique used to root sections of stem on the parent plant without bringing them down to soil level.
Layering will only produce a small number of new plants. Commercial techniques such as French layering and serpentine layering (see below) are no longer used much, but can produce a larger number of new plants and are feasible for home gardeners.
How to layer plants
There are several methods of layering that can be used. Here are the details for four of the most common.
This technique works well for shrubs with shoots that can be bent down to ground level.
- Choose flexible young shoots on the outside of the plant that can be bent down to ground level
- Mark the point where the shoot touches the ground with a bamboo cane
- About 30cm (1ft) from the shoot tip, make a 2.5-5cm (1-2in) incision along the stem, running through a leaf bud (remove the leaf first if the plant is in leaf). This will create a wedge that is propped open with a small piece of wood
- Apply hormone rooting compound to the surfaces of the wound
- Make a shallow trench in the soil, 10-15cm (4-6in) deep, back from the bamboo cane towards the parent plant
- Peg the wounded section of stem into the trench with a loop of thick wire
- Secure the tip of the shoot to the bamboo cane, so that it is growing upwards
- Fill up the trench with soil, firm in and water if dry
Roots should develop within 12 months. When a good root system has formed, sever the layer from the parent plant and transplant to its final position, or into a pot for growing on.
This technique works well for blackberries and hybrid berries.
- In mid- to late spring, choose a long arching stem that easily reaches ground level
- Bury the tip of the shoot 7.5cm (3in) under the surface of the soil. Peg it down (if necessary) with a loop of thick wire. Water if dry
Roots should develop from the shoot tip by the following autumn or spring.
Other methods of layering
French layering involves cutting back the parent plant hard in spring to produce lots of new stems near ground level. The following spring, these new shoots are pegged down on to the soil like the spokes of a wheel radiating out from the base of the plant. As side shoots grow upwards from these stems, soil is mounded over them to encourage rooting. By the autumn or the following spring, these rooted sections can be separated and planted out independently.
This technique is only suitable for shrubs that grow vigorously, such as Cotinus, Cornus and Prunus tenella.
Serpentine layering involves looping the stems of climbers in and out of the soil to encourage roots to form at several points along the same stem. The technique for each buried section is very similar to simple layering. Thin-stemmed climbers need not be wounded.
This technique is suitable for climbers with long flexible stems, such as Clematis, honeysuckle, Humulus lupulus, Parthenocissus, Vitis, Wisteria and Hydrangea anomala subsp. petiolaris.