by Marilyn Homewood, Master Gardener in Training

“A seemingly magic process of creation”

Layering is an asexual (vegetative) method of plant propagation that produces genetic replicas of the parent plant. In this technique, the newly developing offspring remains attached to the parent plant.  This keeps it supplied with water, carbohydrates and nutrients avoiding some of the pitfalls of traditional cuttings.

What makes this possible is totipotency. Every cell in any plant—except for egg and sperm —is capable of regenerating into a complete organism or differentiating into specific cell tissues. Under appropriate conditions, a cell can be induced to multiply into roots, shoots, leaves, or flowers.  One example of this is the formation of adventitious roots.  These are roots that form from “non root” tissues.  Growth of these roots are promoted in part by the plant’s own hormone auxin.

“Wounding” the shoot being layered by making a small sloping shallow cut on the underside of the stem/branch induces this process.  Wounding is known to produce adventitious roots by increasing levels of auxin at the wound site and by forming callus (dedifferentiated plant tissue capable of becoming roots).

Simple Layering

• Select a young vigorous shoot that is low to ground
• Wound stem, keeping wound slightly open using matchstick
• Dust with rooting hormone
• Dig shallow hole, set stem in contact with soil,
• Secure stem in place (u-shaped pin or rock)
• Fill hole and mulch to keep moist
• Check for roots in fall, sever from parent and replant new shrub
• Recommended for climbing roses, forsythia, honeysuckle and boxwood

Tip Layering

• Works well on plants with long whippy stems like berry crops
• Tip of shoot is pegged into soil, secured and buried at point of contact
  

Serpentine Layering

• Similar to simple except that multiple points are wounded and buried
• Good for plants that produce long shoots such as clematis, grapes, wisteria, rambler roses, vining honeysuckle, willow and viburnum
  

Stooling/Mounding

• Process encourages masses of basal shoots which are allowed to layer naturally
• Cut parent shrub back to near ground level in dormant season to encourages masses of basal shoots
• In spring, when shoots are at 15cm, they are covered with dirt leaving tips exposed
• Repeat process as shoot grow to 25 cm
• Buds inside dirt will form roots
• When plant reaches dormancy again, remove soil and newly rooted shoots and plant on
• Recommended for this technique are smoke bush, dogwoods, spirea, daphne, magnolia, cotoneaster
  

Resources

Bryant, Geoff (1992) Propagation Handbook, Basic Techniques for Gardeners, Stackpole Books

Dunn, Bruce (Feb. 2017) Layering Propagation for the Home Gardener, Oklahoma State University Extension, http://extension.okstate.edu

Evans, Ervin, Blazich, Frank (Jan. 1999) Plant Propagation by Layering, North Carolina State Extension, http://content.ces.nscu.edu

Rich, Lee (2007) Making More Shrubs, http://finegardening.com

Stefman, Bianka, Rasmussen, Amanda (2016) Physiology of Adventitious Roots, Plant Physiology, Vol 170 pp 603-617.

Yadav, Deependra, Sing, S.H. (2018) Vegetative Methods of Plant Propagation: I- Cutting, layering, budding, Journal of Pharmacognosy and Phytochemistry, 7 (2) 3267-3273.