LAYERAGE AND CUTTAGE

Layerage and cuttage are a means of propagation whereby parts of a plant are induced to develop roots. Layering is commonly used on larger branches and rooting occurs while the branch is still attached to the plant. Smaller branches user for cuttings form roots after being removed from the plant. Both techniques can be used with citrus, but the resulting plants grow on their own roots without using the advantages offered by certain rootstocks. A rooted cutting or layer can be used as a rootstock for desirable scion varieties, but this is not commonly done.

GRAFTAGE

Graftage refers to any process of inserting a part of one plant into or onto another plant in such a way that they will unite and grow as a single unit. The scion is the part of the new combination which is inserted into the other plant and thereby produces the top of the plant, including branches, leaves and, ultimately, fruit. The stock or rootstock is the plant into which the scion is inserted and it produces the root system and lower trunk. The rootstock may be grown from seed, rooted cuttings or layers.

Grafting involves the use of a scion having two or more buds. There are numerous types of grafts including whip, cleft, bridge, in arch, stump, side, inlay bark, approach and others. Grafting is most commonly used to repair existing trees, to top-work existing trees to change varieties, and to produce new plants. Grafting is not commonly practiced with Florida citrus because it is a more difficult means of propagation compared to budding.

Budding involves the use of a scion with only a single bud attached to a piece of bark. It may or may not include a thin sliver of wood under the bark. Budding is the most commonly used technique for propagating new plants, but it is also used to top-work existing trees to a new variety. It is simple and easy to do, so anyone can be successful after a little practice.

There are several different methods of budding, including T, inverted T, chip (hanging), patch and others. Those most commonly used in citrus propagation are the inverted T bud and the chip bud (hanging bud). The inverted T bud is used when the bark is slipping (easily separated from the wood), whereas the chip (hanging) bud is used at other times.

SELECTING BUDWOOD

Buds should be collected from a tree or trees of the desired variety. Budsticks are commonly selected from the next to last growth flush (the wood behind the current flush) and from the current growth flush after it has matured and hardened. Older growth flushes can be used if the bark still is green.

Round twigs about the size of a pencil are preferred. The buds located in the axils of the leaves (where the leaf is attached to the wood) should be well developed, but still dormant.

After the budwood is cut from the tree, the undesirable wood and/or growth flush should be removed and the remaining budwood should be trimmed to lengths of 20-25 cm (8-10 inches). The leaves should be cut off leaving a stub of the petiole 3-4mm (1/8 inch) long to protect the buds.

Trimmed budsticks should be labeled and used immediately or placed in plastic bags in a cool place. Include a moist paper towel to maintain turgidity and freshness. The label should include the variety, date of collection and source. Budsticks are usually tied in bundles for ease of handling.

STORING BUDWOOD

It is desirable to use budwood as soon after collection as possible, but it can be stored for several months under proper conditions. The bundled budsticks should be sealed in a plastic bag and stored in a refrigerator. The optimum storage temperature is five degrees C (40 degrees F); it should not be allowed to go below two degrees C (35 degrees F). The vegetable drawer of the refrigerator is the best place.

Stored budwood should be checked every couple of weeks for the presence of mold or excess moisture in the bag. Budwood lightly affected with mold should be carefully washed in cold mild soapy water, rinsed, and rebagged in a clean bag. Excessively moist budwood can be lightly blotted on paper towels. Moldy, shriveled or darkened budwood should be discarded, as the buds probably will be dead.

When using stored budwood, it should be kept cool and moist. A good idea is to take enough budwood for a couple of hours use from storage.

BUDDING

Budding can be done anytime there is a suitable stock on which the bark is slipping and when suitable budwood is available. Usually, the bark is slipping from April to November, depending on location. To produce new plants choose rootstocks of pencil size to 2 cm (3/4 inch) diameter, either seedlings or rooted cuttings. The area to be budded should be pruned clean of thorns and twigs. The preferred budding height is 15 cm (6 inches) above ground level.

Preparing the Rootstock
A very sharp knife is used to make a vertical cut in a smooth area of the rootstock about 2.5-3.5 cm (1.0-1.5 inches) long through the bark, deeply enough into the wood to be certain the bark has been completely cut. A horizontal cut about 1 cm (0.5 inch) long is made through the bark at the top (T) or bottom (inverted T) of the vertical cut, again cutting completely through the bark. At the finish of this cross cut, the knife blade is turned slightly upward and given a slight twist to open the bark at the T. The point of the knife can be used to lift the bark along the vertical cut if necessary.

Cutting the Bud
Cut a bud from the budstick while holding the apical end of the budstick away from you. Start the cut about 1 cm (0.5 inch) above the bud and finish a little less distance below the bud. The knife should be held almost parallel to the axis of the budstick, cutting towards the thumb.

Cut only deep enough to take a thin sliver of wood under the bark. The bud should not be scooped out, as this causes too much wood to be taken.

Inserting the Bud
Insert the bud shield under the bark flaps of the stock so that the cut surface is flat against the wood. The bud shield should be completely enclosed in the T; if part of it protrudes, cut it off.

Wrapping the Bud
Wrap the bud with budding tape {polyethylene strips about 1 cm (1/2 inch) wide and 15-25 cm (6-10 inches) long}.

Start the wrap below the bud with 3-4 turns, finishing with several turns above the bud. The end is secured beneath the last circular turn of the wrap. Wrapping should be firm without being excessively tight.

Forcing the Bud
The wrapping should be removed after 2-3 weeks, as union with the stock should have occurred by that time. The bud is then forced into growth by lopping the rootstock. Cut about 3/4 of the way through the stock, on the same side as the bud and about 4-6 cm (1.5-2.5 inches) above it; then push the top over to lay on the ground. The lopped top portion continues nourishing the rootstock and increases the chances of survival of the new plant.

After the bud has grown several inches, the rootstock top can be removed completely by making a sloping cut (high end on the same side as the bud) about 1 cm (1/2 inch) above the bud.

As the bud grows, it will need to be staked and tied at regular intervals to prevent breakage. Remove all other buds and suckers from the rootstock as they appear.

Sources: Citrus Propagation For Homeowners by L.K. Jackson, University of Florida, Institute of Food and Agricultural Sciences (UF/IFAS); Plant Grafting, no. 7.223 by J.E. Ells and H.G. Hughes, Colorado State University Cooperative Extension. 1995-1999