Layering has evolved as a common means of vegetative propagation of numerous species in natural environments. Layering is also utilized by horticulturists to propagate desirable plants.
Natural layering typically occurs when a branch touches the ground, whereupon it produces
adventitious roots Important structures in plant development are buds, shoots, roots, leaves, and flowers; plants produce these tissues and structures throughout their life from meristems located at the tips of organs, or between mature tissues. Thus, a living pla ...
. At a later stage the connection with the parent plant is severed and a new plant is produced as a result.
The horticultural layering process typically involves wounding the target region to expose the inner stem and optionally applying rooting compounds. In ground layering or simple layering, the stem is bent down and the target region is buried in the soil. This is done in
plant nurseries
A nursery is a place where plants are propagated and grown to a desired size. Mostly the plants concerned are for gardening, forestry or conservation biology, rather than agriculture. They include retail nurseries, which sell to the general p ...
in imitation of natural layering by many plants such as
bramble
A bramble is any rough, tangled, prickly shrub, usually in the genus ''Rubus'', which grows blackberries, raspberries, or dewberries. "Bramble" is also used to describe other prickly shrubs, such as roses (''Rosa'' species). The fruits inclu ...
s which bow over and touch the tip on the ground, at which point it grows roots and, when separated, can continue as a separate plant. In either case, the rooting process may take from several weeks to a year.
Layering is more complicated than taking cuttings, but has the advantage that the propagated portion continues to receive
water
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...
and
nutrient
A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...
s from the parent plant while it is forming roots. This is important for plants that form roots slowly, or for propagating large pieces. Layering is used quite frequently in the propagation of bonsai; it is also used as a technique for both creating new roots and improving existing roots.
Method and process
A low-growing stem is bent down to touch a hole dug in the ground, then pinned in place using something shaped like a
clothes hanger
A clothes hanger, coat hanger, or coathanger, is a hanging device in the shape/contour of:
* Human shoulders designed to facilitate the hanging of a coat, jacket, sweater, shirt, blouse or dress in a manner that prevents wrinkles, with a lowe ...
hook and covered over with soil. However, a few inches of leafy growth must remain above the ground for the bent stem to grow into a new plant. Removing a section of skin from the lower-facing stem part before burying may help the rooting process. If using
rooting hormone
Auxins (plural of auxin ) are a class of plant hormones (or plant-growth regulators) with some morphogen-like characteristics. Auxins play a cardinal role in coordination of many growth and behavioral processes in plant life cycles and are essenti ...
, the stem should be cut just beneath a
node
In general, a node is a localized swelling (a "knot") or a point of intersection (a vertex).
Node may refer to:
In mathematics
* Vertex (graph theory), a vertex in a mathematical graph
*Vertex (geometry), a point where two or more curves, lines ...
. The resultant notch should be wedged open with a toothpick or similar piece of wood and the hormone applied before burying.
The buried stem part then grows new roots which take hold in the soil while the above parts grow as individual new plants. Once the end of the stem has grown long enough the process can be repeated, creating the appearance of a row of plants linked by humped, intermittently buried stems. Better results can be achieved when the top of the plant is closer to the vertical.
Once the process is completed, the buried section should be kept well-watered until roots begin to form. The new individual plant may require one to two years before it is strong enough to survive on its own. When it is, the original stem should be cut where it enters the ground, thereby separating the two plants.
Plants types and benefit
As layering does not involve
sexual reproduction
Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote tha ...
, new plants are effectively clones of the original plant and will exhibit the same characteristics. This includes flower, fruit and foliage. Plant selection usually involves plants with a flexible stem.
Simple layering can be more attractive when managing a cascading or spreading plant. These plants tend to propagate in this manner anyway, and potting a new limb will give extra plants without having to sow new seed.
Simple layering can also help when a plant has overgrown its pot and is drooping over the side. The long stem is layered into another pot until it roots, thus bringing it back to soil level.Simple Layering of an Indoor Plant Part 2
Missouri Botanical Garden
The Missouri Botanical Garden is a botanical garden located at 4344 Shaw Boulevard in St. Louis, Missouri. It is also known informally as Shaw's Garden for founder and philanthropist Henry Shaw. Its herbarium, with more than 6.6 million ...
(In depth practical instructions with detailed photographic illustration, specific to indoor varieties)
Ground layering
Ground layering or mound layering is the typical propagation technique for the popular Malling-Merton series of clonal
apple
An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple fruit tree, trees are agriculture, cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, wh ...
root stocks, in which the original plants are set in the ground with the stem nearly horizontal, which forces side buds to grow upward. After these are started, the original stem is buried up to some distance from the tip. At the end of the growing season, the side branches will have rooted, and can be separated while the plant is dormant. Some of these will be used for
grafting
Grafting or graftage is a horticultural technique whereby tissues of plants are joined so as to continue their growth together. The upper part of the combined plant is called the scion () while the lower part is called the rootstock. The succ ...
rootstocks, and some can be reused in the nursery for the next growing season's crop.
Ground layering is used in the formation of visible surface roots, known as "nebari", on bonsai trees.
Air layering
In air layering (or marcotting), the target region is wounded by an upward 4 cm long cut and held open with a toothpick or similar, or a strip of bark is removed. The wound is then surrounded with a lump of moisture-retaining medium such as
sphagnum moss
''Sphagnum'' is a genus of approximately 380 accepted species of mosses, commonly known as sphagnum moss, peat moss, also bog moss and quacker moss (although that term is also sometimes used for peat). Accumulations of ''Sphagnum'' can store w ...
or
cloth
Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, different fabric types, etc. At first, the word "textiles" only referred to woven fabrics. However, weaving is not the ...
, and then further surrounded by a moisture barrier such as
plastic
Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptab ...
film tied or taped to the branch to prevent moisture loss or ingress of too much water as from rain.
Rooting hormone
Auxins (plural of auxin ) are a class of plant hormones (or plant-growth regulators) with some morphogen-like characteristics. Auxins play a cardinal role in coordination of many growth and behavioral processes in plant life cycles and are essenti ...
is often applied to the wound to encourage root growth. When sufficient roots have grown from the wound, the stem is removed from the parent plant and planted, taking care to shield it from too much sun and to protect it from drying out until the new roots take hold. It can take the layer from a few weeks to one or more growing seasons to produce sufficient roots; this is largely dependent on the plant species and the vigor of the parent plant.
See also
*
Coppicing
Coppicing is a traditional method of woodland management which exploits the capacity of many species of trees to put out new shoots from their stump or roots if cut down. In a coppiced wood, which is called a copse, young tree stems are repeate ...
*
Hedge laying
Hedgelaying (or hedge laying) is a countryside skill that has been practised for centuries, mainly in the United Kingdom and Ireland, with many regional variations in style and technique. Hedgelaying is the process of partially cutting throug ...