Technology of vegetative propagation of ornamental plants by layering and grafting

Propagation by layering allows obtaining viable nursery plants without the risk of young shoots dying, as they continue to receive nutrients from the mother plant. This method is indispensable for crops that are difficult to root, as it does not require strict control of humidity and temperature of the environment. However, the technology is quite labor-intensive and yields a small output of finished nursery plants. For this reason, in commercial floriculture, layering is used less frequently than other methods of vegetative propagation">methods of vegetative propagation.

Methods for obtaining layers: horizontal, vertical, and air layering

To obtain horizontal layers, young dormant shoots are used in early spring. They are laid out radially in furrows, pinned to the prepared soil, and earthed up as the vertical shoots grow, 2 to 4 times per season. Rooting is stimulated by longitudinal incisions in the bark or by wrapping copper wire around the base of the shoot in 2–4 turns. By autumn, several new plants are formed from each branch. The method is suitable for the propagation of hydrangea, roses, and lilac.

Vertical layers are obtained by repeated earthing up of young shoots to one-third or one-quarter of their height. This method is effective for hydrangeas and peonies. Work with peonies begins in the second half of April, raking soil away from the bushes to expose the buds. The stems are covered with a light mixture of sod soil, humus, and sand, and a bottomless box is installed to retain the soil and moisture.

• Age of mother peonies — 4 years and older
• Number of shoots per bush — 10–20 pcs.
• Height of the box — 25–30 cm
• Period until flowering — in the 3rd year

When growing vertical peony layers, the box is initially filled with the soil mixture halfway, and as the shoots grow, more soil is added. To awaken dormant buds, the tops of the shoots are pinched, and regular irrigation is organized. In early September, the boxes are removed, the stems are unearthed, and the rooted shoots are cut off. They are transferred to nursery beds, where the young plants bloom in the third year.

Air layering is used for breeding evergreen crops, such as azalea, dracaena, magnolia, ficus, and yucca. This method allows roots to be obtained directly on the branches of an adult plant. The success of the procedure directly depends on the age of the selected shoot.

1. Clear the leaves from the shoot for a length of 30 cm at the site of the intended rooting.
2. Make an inclined "tongue" incision towards the center of the stem or remove a ring of bark 5–12 mm wide around the circumference.
3. Insert damp sphagnum moss into the incision with the back of a knife blade so the edges do not fuse.
4. Place the shoot in a dark polyethylene sleeve, tie it at the bottom, fill it with damp sphagnum, and tie it tightly at the top.
5. Leave the layer on the plant for a year, periodically checking and moistening the moss. After roots appear, cut off the rooted shoot below the root ball.

Grafting technology and rules for scion harvesting

Grafting is a way of creating a plant with new properties through the artificial fusion of a rootstock and a scion. The method is widely used in ornamental gardening when growing roses, lilac, cacti, lemon, azalea, and camellia. Plants can be grafted both in open soil and in greenhouses, where winter grafting is most commonly practiced.

Scion material is harvested in the form of cuttings and buds from the upper or middle part of the mother plant's canopy, using the previous year's growth. For summer grafting, shoots are cut immediately before the procedure, as they lose moisture quickly. For winter and spring work, cuttings are harvested in advance — in November or December, before the onset of severe frosts, when the plants are in a phase of deep dormancy.

Growing rootstocks and budding technique

For the rootstock, plants of the same species as the scion are used. Nursery plants are grown from seed for 1–3 years in open soil or in containers, ensuring that transplanting and nursing are carried out.

• Duration of rootstock cultivation — 1–3 years
• Age of rootstock for budding — 2–3 years
• Diameter of rootstock trunk — 0.7–1.5 cm
• Height of budding at the root collar — 6–10 cm
• Height of budding on the trunk — 0.6–2.0 m

For the work, prepare budding, grafting, and pruning knives; in rare cases, scalpels and blades may be useful. Cuttings are cut using pruning shears. For tight binding of the components, use strips of synthetic film, thin rubber, or strong wool and cotton threads.

Budding is a method of grafting using a single bud (eye) with a small piece of bark (shield). It is carried out during periods of active sap flow, when the rootstock bark easily separates from the wood. In spring, it is grafted with a sprouting bud, and in summer (in July–August) — with a dormant one.

Procedure for simple budding:

1. Take the scion shoot in your left hand with the top facing you. Using a budding knife, cut the shield with the bud so that the cut starts 1–2 cm below the bud and ends above it.
2. Remove the wood from the shield (this is necessary for most tree species). For summer grafting, leave a leaf stalk 4–6 mm long on the shield.
3. Make a T-shaped incision in the rootstock bark down to the wood and carefully lift the bark on both sides of the incision.
4. Insert the shield with the bud into the formed gap under the lower edge of the horizontal cut and bind the graft site tightly.

Bud grafting (chip budding) is a reliable method for roses, lilacs, and other deciduous species. In this case, the shield is fitted to a side cut on the rootstock rather than into a T-shaped incision. For structural strength, a special tongue is made on the rootstock.

Grafting with a cutting: whip grafting, bark grafting, and chip grafting

Whip grafting is used when the diameters of the scion and rootstock match perfectly. For simple whip grafting, cuttings with 3–5 buds are taken from the middle or upper part of a shoot. The top cut is made with a sharp knife just above a bud, and the bottom cut is made in the form of a wedge 2.5–4 cm long, ending right below the bud. A similar cut is made on the rootstock, after which the components are connected, bound, and the top is covered with garden wax.

Tongue-whip grafting helps to secure the components more firmly and avoid their displacement. For this, longitudinal tongue-shaped incisions 1–1.5 cm long are made on the slanted cuts of the rootstock and scion, one-third of the way from the ends of the cuts. When joined, the tongues must fit tightly into each other.

Bark grafting is carried out during spring sap flow or in winter. This method is excellent for mature trees and top-working. For greater strength, the slanted cut on the scion can be made with a shoulder.

Procedure for bark grafting:

1. Cut off the rootstock shoot above the future graft site.
2. Make a longitudinal incision in the rootstock bark down to the wood.
3. Prepare the scion cutting: make the bottom cut slanted and the top one straight, 3–4 cm above the bud.
4. Insert the cutting under the bark so that the lower bud is 3–4 mm below the rootstock end, and the start of the slanted cut is 3–4 mm above it.

Chip grafting is used in cases where the scion diameter is smaller than the rootstock diameter. It is performed with or without a tongue, preparing the cuts on the cutting in the same way as in whip grafting.

Cleft grafting is performed in late winter, spring, or summer. It is best to start the work in spring, before the buds begin to grow actively.

• Slanted cuts are made on both sides of the scion cutting, resulting in a double-sided wedge.
• The top part of the rootstock shoot is removed and the shoot is split along the axis, slightly longer than the length of the scion's wedge-shaped cut.
• The cutting is inserted into the cleft, ensuring the cambial layers of both components match.

The diameters of the rootstock and scion must match. If there are significant differences in the thickness of the rootstock and scion shoots, several clefts are made and two cuttings are inserted into each, ensuring the cambial layers match on at least one side.